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Storm Water Mgmt-SY 910101 CITY-WIDE -- STORM WATER MANAGEMENT STUDY '-- '- for the City of COPPELL,TEXAS Albert H. Halft' Associates, Inc. January 1991 ~~ i~< C!l '" ::> f- ~~:i O:i:::::;w ~I-W~ c~~ o C!lw a: > Z ~g"'Of- W f- "-Z c:J '" a:::> ~ ~l!: 88 I I I I I . : I ~ -=:3: ~ .....-- I":' I~ I 1 ,r------..-""\. ~;'l- . 1---, ) !!\~\...y 1*..\. O. ~ll OF Tt-!E~;;:-r ~ ~ I ~~_ ----=::4: . ~ I .~ ~- ~ ~ I -.~ 'H~Q ___/ ~-~: ~ I ;f~J~' --_/~/ i ~ I ~O.~Cl!..EEKtI ~- I " R~'v--- ,1 II.;, (~ .-.-\ U, ~ ;; g; ~ ~ ~I ! !II -! - )( 1lI~!il.~ ~ w Ii'~)( ~e ~ ~ ~ ~ ~~ - . =..i ~a ~~~~-' "'I ~ 0 I li:1 ----I "- s ~ 9 ~ < '" I lii ... w 0.0 !< 1 ... it 1 I 1 1 1 I I I 'O^'S l::Uh 1 1 I I ...1 _.;J ~ ~ ~ ~ ~ ~ ~ ~ o o o o c o o '0 o o o o fl l-....J A CITY-WIDE STORM WATER MANAGEMENT PLAN for THE CITY OF COPPELL, TEXAS Prepared by o o o o o o Albert H. Halff Associates, Inc. 8616 Northwest Plaza Drive Dallas, Texas 75225 January 1991 @ Albert H. Halff Associates, Inc. 1991 fr L fI u for o o o o o o THE CITY OF COPPEll.. Mr. Mark Wolfe Mayor Mr. Bill Smothermon Mayor Pro Tern '1 U Mr. David Thomas Mr. Tom Morton Mr. Jim Cowman Mr. Ron Robertson Mr. John Nelson Mr. Peyton Weaver !' i i l i U Councilpersons o Mr. Alan D. Ratliff City Manager o Mr. Steven G. Goram Director, Department of Public Works 11 l...J Mr. Gary L. Sieb, A.I.C.P. Director, Planning and Community Services o o ..-\ U o G Ms. M. Shohre Daneshmand, P.E. Acting City Engineer Mr. Rick Wieland Parks and Recreation Manager Accepted January 29, 1991 Coppell City Council 'I U III ~ .. 111111 _11- 111111 ALBERT H. HALFF ASSOCIATES, INC. ENGINEERS · SCIENTISTS · SURVEYORS DALLAS. ARLINGTON. CHICAGO · FORT WORTH 8616 NORTHWEST PLAZA DRIVE. DALLAS. TEXAS 75225 214/739.0094 January 29, 1991 AVO 10751 ! I ...., -. ...J City of Coppell 732 Deforest Road P.O. Box 478 Coppell, TX 75019 -. I n U Att: Mr. Alan D. Ratliff City Manager o Re: City-Wide Storm Water Management Report Gentlemen: n L Attached is the City-Wide Storm Water Management Study authorized by the City of Coppell on March 27, 1990. This report includes a discussion of the history of flooding, factors affecting flooding, hydraulic and hydrologic methodology, a planning inventory and a discussion of storm water mitigation techniques. It also contains storm water management recommendations and inundation limits and profiles for streams in the City of Coppell. In addition, local drainage problems compiled from citizen complaints are analyzed and solutions proposed. f r ,-I 11 U ,...... I I The draft report was submitted for review on July 3, 1990. Staff review and public comments were received and incorporated into this final report. The final City-Wide Storm Water Management Plan was approved by the Coppell City Council on January 29, 1991. It has been a privilege for our firm to perform this study and help develop a comprehensive storm water management plan for Coppell. We especially appreciate the cooperation of the residents and landowners of Coppell, as well as the members of the City Council and staff, that have assisted in the development of this study. Respectfully submitted, r !"',.~ ~ - ,...... ..' .-,... ..., . ALBERT H. HALFF ASSOCIATES, INC. til--c;4f-: Walter E. Skipwith, P.E. . , .~ . I!. 9LtlM. !/...dUJ C. Jean Hansen, P.E. ~:.'....-:..~~'\ /} s ~:j~~~i 'i ')-4 . - '" '''; -".. :;; '/;1" : . C . -.:: :: l.Jy' ,,;....:,.. ~ -:.- ';- -" <~/". ~':: //,-." ,"!. I, ..;:\'~ ~".",,"-.,::- '(,I'...., .... - ...\'(~~ i \'i~/I'~', /.'1\ \:;, ~ ,'"':, <:J."._.<:.~_ '.,,",,':,,~--..\$:..~ .J t'.. . " / '" -... " r TRANSPORTATION WATER RESOURCES LAND DEVELOPMENT MUNICIPAL ENVIRONMENTAL STRUCTURAL ,---, I SURVEYING GLOBAL POSITIONING SYSTEM (G.P.S.) LANDSCAPE ARCHITECTURE REMOTE SENSING AND MAPPING PLANNING TABLE OF CONTENTS CITY-WIDE STORM WATER MANAGEMENT STUDY CITY OF COPPELl, TEXAS pag:e Letter of Transmittal ........................................... v Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiv List of Photographs ............................................ xv List of Plates in Appendix F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi Acknowledgements ............................................. xvii Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix 1. Introduction 1-1 A Objectives of the Study ..................................... 1-1 B. Scope of the Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 C. Description of the Watershed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6 D. History of Flooding ........................................ 1-6 1. Hydrologic Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6 2. Historic Floods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7 3. Storm Water Management Before 1990 . . . . . . . . . . . . . . . . . . . . . 1-8 4. Flood Frequency Analysis ............................... 1-10 E. Flood Plain Regulations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11 F. Degree of Protection ....................................... 1-11 II. Flooding Information ......................... .'. . . . . . . . . . . . . . . . . 11-1 r- A Climatic Factors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1 1. Frequency and Duration of Rainfall ....................... 11-1 2. Time Distribution of Rainfall ............................ 11-2 3. Areal Distribution of Rainfall ............................ 11-2 4. Direction of Storm Movement. . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2 5. Initial Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2 B. Physiographic Factors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-3 1. Basin Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-3 a. Geometric Factors ................................ 11-3 b. Soils and Infiltration Losses . . . . . . . . . . . . . . . . . . . . . . . . . 11-4 c. Physical Factors ....... . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-4 2. Channel and Flood Plain Characteristics .................... 11-5 a. Carrying Capacity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-5 i. Cross Section ................................. 11-5 ii. Slope of the Stream Bed . . . . . . . . . . . . . . . . . . . . . . . . . 11-6 iii. Resistance to Flow ............................. 11-6 b. Valley Storage ................................... 11-8 i. Definition.................................... 11-8 ii. Previous Studies ............................... 11-8 vii ~ ,-----, €-AI €-AI 1-AI 1-AI 1-AI 1-AI 1-AI ..... ffiA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. SUOJlllln1i~'M UOHJtulSUo;:) '€ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. suonlllng~'M UOJSJAJpqnS 'Z . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. gUJUOZ ~Sn pUlrl '1 . . . . . . . . . . . . . . . . . . . . . . ~JOswW UOnU~^~ld ~gllwlla IlllnlJtulSUoN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. UOHJJ~ld pooH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. UOHllJ!TIpoW l~qlll~M. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . uOHJnpOllUl 'a 'J 'S: 'V 1-AI .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . uOHllgmw ~gllwlla pooH 'AI r- 0€-II1 6Z-II1 6Z-II1 6Z-II1 9Z- III SZ-II1 SZ- III SZ-II1 ZZ-II1 ZZ- III OZ- III 61-II1 61-II1 61-II1 91-II1 Sl- III Sl-II1 Sl- III €1-II1 01- III 01-II1 8- III 9- III 9- III Z-II1 Z-II1 1-II1 1-II1 1-II1 ,----- ..... r- r- . . . . . . . . . . . . . . . . . . .. ^lHllnQ l~lllM. pUll IJOUn'M l~lllM. Wl01S '€ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . mlla AlnllOQ l~lllM. 'z . . . . . . . . . . . . . . . . . . . . . . . . . . llJl~lJlJ IllJO'l pUll ~lms 'Illl~~d '1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. AlnllOQ l~lllM. . . . . . . . . . . . n~ddo;:)}o AlD ~ql UJ uomsod~a pUll UO!S013 'J . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. UO!S013 I~uullqJ 'q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . UO!S013 ~qSl~lllM. 'll . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. uomsod~a pUll UOJS013 '6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~l!S gUJPOOH '8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ~l!S IllsodSJa ~lSllM. pnos 'L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~SllJ ffid gUJ1SJX3 '9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ~Hn!ln 'S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ~HnPlld UOHllllOdsulll~. '17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. dJqSl~lL\\() Au~dold '€ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. gUJUUllld oolldS u~dO 'z . . . . . . . . . . . . . . . . . . . . . . . ~nIllA JJUooS pUll S:)n~ql~V IllJOlllN '1 . . . . . . . . . . . . . . . . . . .. AI01U~^UI gUJUUllld lu~W~gllUllW l~lllM. Wl01S . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ~sn pUlrl ~dOI~^~a ^nnd '€ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~sn pUlrl gUJ1SJX3 'z . . . . . . . . . . . . . . . .. ~l!S IllJ~OIoollqJlV pUll ~sn pUlrl JJl01SJH '1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~gUllqJ J!qdll~ow~a pUll ~Sn pUlrl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~mpI!M. 'z . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. UO!llll~g~A '1 . . . . . . . . . . . . . . . . . . . ~mpI!M. "iJ UO!llll~g~A - lU~UIUOlJAu3 IllJ~OIO!S: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. STIoS '€ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ,{gOIooD 'z . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~lllwnJ '1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lU~UIUOlJAu3 IllJ!sAqd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . uO!pnpOllUl 'd '3 'a 'J 'S: 'V 1-111 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. AI01U~^UI gUJUUllJd '111 n-II 01-11 01-11 6-11 6-11 ~~lld . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~!pnlS l~qlO 'q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . uOHlllqnllJ 'll . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. OOU~llroUo;:) ~mold 'Z . . . . . . . . . . . . . ; . . . . . . . . . . uonmndwo;:) ~mOld oollpns l~lllM. '1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . UOHllWlOJUI UJllJd pooH (p.JDlI!lDOO) S.LN:UNO:J .110 ~nlV.L 'J TABLE OF CONTENTS (continued) E. 4. Tax Incentives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Purchase and Reallocation of Land .. . . . . . . . . . . . . . . . . . . . . . . 6. Public Information and Education . . . . . . . . . . . . : . . . . . . . . . . . . 7. Watershed Management ................................ 8. Debris Removal ...................................... 9. Inspection of Engineering Works. . . . . . . . . . . . . . . . . . . . . . . . . . Structural Damage Prevention Measures . . . . . . . . . . . . . . . . . . . . . . . . . 1. New Channel Construction or Old Channel Improvements ...... 2. Closed Conduits ...................................... 3. Levees and Floodwalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. Sumps and Pump Stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Reservoirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Flood Retarding Basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7. Raising Ground Elevations .............................. 8. Floodproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9. Watershed Management (Structural) ....................... a. Porous Pavements ................................ b. Infiltration Beds and Dry Wells ...................... c. Parking Lot Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . d. Rooftop Storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Relief Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Public Disaster Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Flood Insurance ...................................... F. V. Design Criteria Pal!e IV-3 IV-3 IV-4 IV-4 IV-5 IV-5 IV-5 IV-5 IV-6 IV-6 IV-6 IV-6 IV-6 IV-7 IV-7 IV-7 IV-7 IV-8 IV-8 IV-8 IV-8 IV-8 IV-9 V-I A Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V-I B. Floodway Capacity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V-I C. Channelization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V-I D. Slopes in Cut and Fill ...................................... V-2 E. Levees, Berms, and Floodwalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V-2 F. Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V-3 1. New Bridges ......................................... V-3 2. Existing Bridges ...................................... V-3 G. Culverts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V-5 H. Parkways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V-5 I. Land Acquisition .......................................... V-5 J. Erosion Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V-6 K. Appearance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V-6 VI. Stream Management Alternatives and Recommendations. . . . . . . . . . . . . . .. VI-I A B. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specific Stream Flooding Sites ................................ 1. Grapevine Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Flooding at Bethel School Road & Hawk Lane .......... b. Erosion Downstream of Denton Tap Road/ Meadowcreek Road ............................... ix VI-I VI-I VI-l VI-2 VI-3 r- Of:- IA 6'l-IA 6'l-IA 6'l-IA 9(;- IA 9'l- IA r-- ~-IA v'l-IA v'l-IA v'l- IA tl-IA tl-IA tl-IA 'l'l- IA O'l- IA O'l- IA O'l-IA 81-IA 81-IA 81-IA Ll-IA Ll-IA 91-IA SI-IA vl-IA vl-IA vl-IA vl-IA €1-IA n-IA n-IA 6-IA 6-IA 6-IA 6-IA 8-IA L-IA L-IA L-IA ~i1Rd x . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 'lJ m~llS '€1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .. UO!S!^!pqnS pu~g )fRO 'q . . . . . . . . 0 . . . . . . . . . . . . . . 0 . . . . 0 . . . . . . . . . pRO~ ~lms 'R . . . . . . . 0 . . . . . . . . . . . . 0 . . . . . . . . . . . . . 0 . . . . 0 . 0 0 IJ m~llS ''l1 . . . . . . . . . 0 0 . . . . . . . 0 0 . . . . . . . .. ~UR'l MonOH gUlPUlA\ .:> . . . 0 . . . . 0 . . . . . . . 0 . . . . 0 . . . . . . ~UlSSOlJ pRO~ ~POOld 'q o 0 . . . . 0 . . . . 0 . . . . . . . . . o. gUlPOOld )flRd UMOlg M~lpUV 'R . . . . . . . . 0 . . . . . . . . . . . . . . . . . . . . . . 0 . .. q:>URlg pOOMUOllOJ 'n . . . . . . . . . . . . 0 . . . . . . . . . . . .. plR^~lnog )flRd ~lRlOd.IOJ 'q . . . 0 0 0 . . . . . . . . 0 . 0 . . . . . . . . . . . . . . 0 0 . . . pRO~ n~ddOJ 'R . 0 . . . . . . . . . . 0 . . . . . . 0 0 . . . . . . . . . . . . . . . . . . . . 0 la m~llS '01 . . . . 0 . . . . . . . . . . . . 0 . . . . . . ARMmdS )flRd UMOlg M~lPUV 'q . . . . . . 0 . . . . . 0 . . . . . . . 0 . . . . . . . gUlPoold pRO~ l~lOJ~a 'R . . . . . . . . 0 0 . . . . . . . . . . . . . . . . . . . . . . 0 0 0 . . . . . )f~lJ UOlU~a '6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . l~^rn Al!U!l.L ~ql JO )flod mra '8 . . . . . 0 . . . . . 0 . . . .. pRO~ ~lOOW JO lSll3 - ~^pa u~lglRpg '1fI pRO~ 100q:>S I~Ql~g U~Ml~g ~gRUlRla lO'1l~^O .~ o . . . . . . . . . . 0 0 . . . . . 0 0 . . . . l~uuRqJ guow ~.IV AqSlRW 'p . . . . . 0 . . . . . . . . . . .. pRO~ ~lOOW JO m~llsdfl uO!lU~l~a .:> . 0 0 . . . . . . . . . 0 . . . . . . . . . .. pRO~ ~lOOW JO m~llSUMOa 'q . . . 0 . . . . . . . . . . . . 0 . . . . . . . . . . . . . . pRO~ 100q:>S l~ql~g 'R . . . . . 0 . . . . . 0 . . . . . . 0 0 0 . . 0 . . . . . . . . . . . . . . . . .. 90 m~llS 'L . . . . . . . 0 . . . . . 0 0 0 0 . . . . . . . 0 . . 0 . . . 0 . . . . . . 0 . .. SD m~llS '9 . . . . . . . . . . 0 0 . . . . . . . . . . . . . . . .. VvD m~llS pUR vD m~llS oS o . . . . . 0 . . . . . . 0 0 . . . . . . . 0 . . . . . 0 0 . . . . . . . . . . .. €D m~llS 'v . . . . . . . . 0 0 . . . . . . . . . . . . . . . . . .. V'lD m~llS pUR 'lD m~llS '€ . . . . . 0 . . . . 0 . . . . . . . 0 0 . . . ARM){lRd UOd~ld JO m~llsdo SlU~m~^Olduq ~gRUlRla JO UO!lRnIR^3 'q . . 0 0 . . . . . 0 0 0 . . . . 0 0 . 0 . . . 0 . . . . . . . . . . . . . pRO~ l~ql~g pUR ARM){lRd llod~ld JO UO!l~Sl~lUJ ~Q.L .g . 0 . . . . . 0 0 . . . . . . 0 . . . . . . . . . . . . . . . . . 0 0 . 0 pRO~ l~ql~g 'J . . . . . . . . . (l:>Rl.1 'H'J'N) ID m~llS JO Almnqp.L ~mRuufl .~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 0 . ~uR'l q:>O'1 'p . . . . . . . . . . . . 0 . . . . . . . 0 0 . . . 0 . . . . . .. (l~llS n~q:>l!W) pRO~ n~ddOJ JO m~llSUMOa UO!S0l3 .:> . . . . . . . . . . 0 . . . . . . . . . 0 0 0 . . . . . . . . . . . . . pRO~ n~ddOJ 'q . . 0 0 . . . . . . . . . . . . . . . . . . ('lS splRH) pRO~ 100q:>S l~ql~g 'R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 0 mR~llS ''l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ~^pa Ul~l~Mqlnos .g . . . . . . 0 . . . . . . . . . . . . . . 0 . . . . . . . .. ~^pa Ul~l~Mqlnos Ol ~ Ul~l~Mqlnos pUR SlnO'1 'lS 'j . . . . 0 0 . . . . . . . . . . . . . 0 0 0 S€9-HI JO m~llSUMOa UO!SOl3 .~ . . . . 0 . . . . . . . . . . . . . . 0 . . . . . . . . 0 . . . . spRO~ l~ql~g pUR 100q:>S I~Ql~g JO UO!l~Sl~lUJ ~ql JO gUlPOOld 'p . . . 0 . . . . . . 0 . . ~ . . . . . 0 . . . .. ~Pl!J POOMARW l~U pRO~ )f~l:>MOp~W lR Almnqp.L ~mRuufl UO UO!SOl3 0:> (panUJlOoo) s.LNllNO:J .!IO 3'IRV.L TABLE OF CONTENTS (continued) Pal!e C. Basin-Wide Management Alternatives. . . . . . . . . . . . . . . . . . . . . . . . .. VI-3D 1. No Action. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-31 2. Valley Storage Preservation. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-31 3. Flood Plain Encroachment Limits . . . . . . . . . . . . . . . . . . . . . . . .. VI-32 4. Storm Water Detention. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-33 a. Regional Detention ............................... VI-33 b. On-Site Detention ................................ VI-33 5. Erosion/Sedimentation Control .. . . . . . . . . . . . . . . . . . . . . . . . .. VI-34 a. No Action ...................................... VI-34 b. Grapevine Creek Downstream of Denton Tap Road/ Meadowcreek Road ............................... VI-34 c. Grapevine Creek Between Freeport Parkway and LBJ Freeway .................................... VI-34 d. Stream G6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-34 e. Denton Creek ................................... VI-34 f. Parkwood Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-34 g. Woodridge Channel ............. . . . . . . . . . . . . . . . . .. VI-34 6. Buffer Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-34 a. Parallel Parkways .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-34 b. Parkway with Drainage Swale System .................. VI-35 7. Open Space Preservation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-37 a. Greenbelt Preservation/Open Space Acquisition . . . . . . . . .. VI-37 b. Hike and Bike Trails .............................. VI-39 D. General Watershed Recommendations ...... . . . . . . . . . . . . . . . . . . .. VI-42 1. Passive Flood Warning & Protection Systems ................ VI-42 2. Survey Monumentation System ........................... VI-42 3. Construction Site Erosion Control ........................ VI-43 4. Construction Plan Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-43 5. Creek Inspection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-43 6. Creek Vegetation Preservation ........................... VI-43 7. Flood Plain Dedication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-44 8. Zoning Map Flood Delineation Revision. . . . . . . . . . . . . . . . . . .. VI-44 9. Park Preserves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-44 10. Urban Storm Water Permits ............................. VI-44 a. Drainage Data Base ............. . . . . . . . . . . . . . . . . .. VI-44 b. Base Maps .............. . . . . . . . . . . . . . . . . . . . . . . .. VI-44 c. Sampling/Gaging/Flood Warning Systems .... . . . . . . . . . .. VI-44 d. Water Quality Management ......................... VI-45 11. Finished Floor Certification ............................. VI-47 12. Flood Plain Ordinance Revisions. . . . . . . . . . . . . . . . . . . . . . . . .. VI-47 E. Recommended Flood Plain Management Plan. . . . . . . . . . . . . . . . . . .. VI-47 VII. Local Drainage Problems - Alternatives and Recommendations. . . . . . . . . . .. VII-1 A Freeport Parkway near Southwestern Boulevard .................. VII-1 B. Bullock and Howell Streets .................................. VII-6 C. Brooks LanelHunterwood Subdivision .......................... VII-8 xi TIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ~lllIeI :d X!pugddy l-g . . . . . . . . . . . . . . . . . . . . . . . . . . . . lIllla :>TInlllpAH }O AIlImmns :3 X!pugddy . I-a . . . . . . . . . . . . . . . . . . . . ~lnprulS ~ggl:::> gUHspg}O AlOlUgAU{ :a X!pugddy 1-:::> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. SlU!lIIdmOJ ggllU!lIla ::::> X!pugddy I-a . . . . . . . . . . . . UlIIeI lUgmggllulIW 19l1lA\ WlOlS gp!A\-At!:::>}O g:)ulIldg:):)y gU!lggW {punOJ At!:::> IlIpgds }O ~lnU!W :a X!pugddy lngddOJ }O At!:::> gql ql!M gUd uo ~pgpnpU{ loN] 06€L8 'oN g:)UlIU!PlO U!lIIeI pooH ngddOJ }O At!:::> :v X!pugddy I-IX Aqdll~OTIq!a 'IX I-X ~lON pug -x I-XI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SWlg.1}O AlllSSOID 'XI 6-I1IA .............................................. SUO!snI:>UOJ 'a 8-I1IA ..................................... Sg:)lnOS gU!pund 19q1O .:::> L-I1IA ................................ UOHlIlUgmgIdUII 9 gSllqeI '9 L-I1IA ................................ UOHlIlUgmgIdUII S; gSllqeI 'S; 9-I1IA ................................ UOHlIlUgmgIdUII V gSllqeI 'v S;-I1IA ................................ UOHlIlUgmgIdUII € gSllqeI. '€ v-IlIA ................................ UOHlIlUgmgIdUII Z gSllqeI 'Z Z-I1IA ................................ UOHlIlUgmgIdUII 1 gSllqeI '1 Z-I1IA .................................... SlUgmgAOldUII}O gU!SlIqeI 'a I-IlIA ....................................... Atmq!SlIgd :>!Wouoo3 V I-IlIA .............................. UlIIeI pgpugmmoog'M}O UO!llllUgmgIdUII 'I1IA Iv-IIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. SUO!snI:>UOJ '.1 Dv-IIA . . . . . . . . . ~wnlS gUPgg~ug 19vo pUll ~lV mgIQOleI snooulIng:)S!W 'S 6€-IIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . g:)UlIUglU!lIW ggllU!llla AlIMPllO'M ''M 6€-IIA . . . . . . . . . . . . . . . . . . . .. lUgmg:)lIIdg'M IlIJUlIeI pUll g:)UlIUglU!lIW 1991lS '0 L€-IIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. gUlI'1 }~IgIdllw 'eI v€-IIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IgUUllq:::> ggPPPOOA\ '0 v€-IIA . . . . . . . . . . . . . . . . . . . . . . . . . pllO'M g~lI'1 APUlISlplllAgInOa lnqlJy:>lIW 'N Z€-IIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Uo!S!^!pqns SM.Op~W 'W O€-IIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. PlllAgInOa IgnmllsJpllo'M glOOW '1 LZ-IIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IgUUllq:::> pOO~llIeI "}I 9Z-IIA . . . . . . . . . . . . . . . guwooId 1991lS gUlI'1l~l:)MOpllqSlgApa n01l)l ApUlIS 'f vZ-IIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. gApa UlIMS pUll gUlI'1 ~MlIH 'I ZZ-IIA . . . . . . . . . . . . . . . . . . . .. (UOH!PPY ~~S nguuOJ) gUlI'1 gIlIa AplIqS 'H 61-IIA . . . . . . . . . . . . . . . . . . . .. plIO'M g~lI'1 ApUlIS III gApa smH gupgdSJqA\ 'D Ll-IIA . . . . . . . . . . . . . . . . . . . .. uOHWPY g:)lIIeI 19mmns ~llllsg POOMUOllOJ 'd vl-IIA . . . . . . . . . . . . . . . . . . . . . . . . . .. ~llleI gmoH gUqoW gIgulIP.1 UgPIOD 'g n-IIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. SlggllS gA~ pUll AqZOJ 'a golleI (panopooo) Sl.N~O:J ~O 3'1HV.L 1-1 1-2 1-3 1-4 II-I 11-2 11-3 11-4 11-5 11-6 III-I III-2 III-3 III -4 III-5 III -6 III-7 III -8 III-9 III-lO III-11 V-I LIST OF TABLES Streams in the Coppell Storm Water Management Study ............................................... Specific Flooding Sites Identified by Natural Drainage Subcommittee .................................... Trinity River Basin Stream Gaging Stations in the Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pertinent Data on Corps Lakes in the Upper Trinity River Study Area .................................... Point Rainfall Data for Coppell Area (inches) from TP-40 .................................................... Seasonal Rainfall Limits for AMC-Total 5-Day Antecedent Rainfall. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Loss Rates - Block and Uniform Method .............................. Roughness Coefficient Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Summary of Discharges - Minor Tributaries ............................ Comparison of Discharges - Major Streams. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Soils of the City of Coppell ........................................ Mammal Species within the Study Area ............................... Fish Species within the Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Historical and Archaeological Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Population Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Existing and Proposed Parks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Existing and Proposed Flood Plain Fills ............................... Stream Flooding Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Local Drainage Problem Flooding Sites ............................... Erosion Sites ................................................... Elm Fork Trinity River Water Quality Data ............................ Flooded Stream Crossings - Safety Ratings Page 1-3 1-4 1-7 1-8 II-I 11-3 11-4 11-7 11-11 11-12 III -4 III-9 III-lO III-12 III-13 III-18 III-21 III-23 III-24 III - 26 III-3D V-4 VI-I Parkway/Swale System Land Development Cost Comparisons ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-35 VI-2 Recommended Greenbelt Additions .................................. VI-37 VI-3 Recommended Wildflower Species for Greenbelt Preservation Areas ...................................... VI-38 VI-4 Passive Warning and Protection Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VI-42 VI-5 Specific Stream Flooding Site Alternatives - Summary of Recommendations ..................................... VI-48 VI-6 Basin-Wide and General Watershed Alternatives - Summary of Recommendations ..................................... VI-49 VII-l VII-2 -. Local Drainage Analysis Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VII-2 Local Drainage Problem Sites - Summary of Recommendations ..................................... VII-42 xiii 8€-IIA 9€-IIA €€-IIA l€-IIA 6Z-IIA gz-IIA SZ-IIA a-IIA lZ-IIA 81-IIA 91-IIA H-IIA 01- IIA L-IIA S-IIA 9V"IA I1tIA 9€-IA 8Z-IA lZ-IA 61-IA Zl-IA O1-IA 9-IA S-IA Z-AI gz-Ill LZ- III tl-Ill S-Ill 6-1 S-I 30Vd AIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ~Ue'J JWI~Idgw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. I~UUgq;) ~~PPPOO1\\ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. UO!S!^!pqnS SMOpWW . . . . . . . . . . . . . . . . . . . . . . . . . . .. p1M~Inog I~nures PUg pgo'8 ~lOOW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I~UUgq;) POOM111gd . . . . . . . . . . . . . . . . . . . . . . . . ~Ue'J l~.J:)MOpgqS PUg ~^PQ noU)l ,{PUgs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ~^PQ UgMS PUg ~Ue'J lIMgH . . . . . . . . . . . . . . . . . . . . . . . . . . . .. (~~SIII~uuO;)) ~Ue'J ~IgQ ,{pgqS . . . . . . . . . . . . . . . . . .. pgo'8 ~1Ie'J ,{ptrnS '1\\ 19 pgo'8 smH ~up~dS!ll!t\ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. OOgId l~UIWns PUg pOOMUOnO;) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1I1gd ~moH ~TIqoW ~~UgpJ.. U~PIOD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Sl~llS ~,{-e)l PUg ,{qzO;) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . pooA\l~lunHl~ue'J S1(OOlg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 'lS n~MOH PUg 'lS lI:>onng . . . . . . . . . . . . . . . . . . . . . . . 'P^Is: Ul~l~Mqlnos 1WU ,{gA\1{lgd 1l0d~ld . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ~~go ~~glS-l~l;) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ugld oogds u~dO ~l!sodmO;) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. lu~mdoI~^~Q Uo!S!^!pqns 10J ~^nllUl~lIV ~~llU!lllQ . . . . . . . . . . . . . . . . . . . .. q:>Ug1g pOOMuonO;) - ~Ue'J MonOH ~U!PU!1\\ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. UOngnlllSUI U!lllQ q:>U~ld P1g~:>gg Ill:>!<L\L - 90 mW1lS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Uon~s SSOl;) Ill:>!<L\L pgO'8 ~lOOW JO mW1lSUMOQ 90 mW1lS . . . . . . . . . . . . . . . .. pgo'8 n~ddO;) JO WWllSUMOQ UO!S013 1 0 mg~llS . . . . . . . . . . . . . . . . . .. 10 mW1lS SlU~m~^OldlIll pllO'8 Iooq:>S I~ql~g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~^ngUl~lIV UO!l"BZIT!qglS I~UUgq;) 1I~1;) ~U!^~dll10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. SWlV Ill:>np;) - IOllUO;) UO!S013 1I~1;) ~U!^~dll10 ........................... . spoql~W UOnll~mw ~~gmgQ pooH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~l!S UO!S013 pUll ~U!PoOH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~I:>A;) UO!S013 I~UUgq;) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. dgW 1~^0;) pue'J . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~l!S Ill:>~OIOOgq:>lV PUg Ill:>pOlS!H 'dgW SUOS Ig1~U~0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0661 's ,{gw - ~U!POOH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,{pnlS JO ~dooS 3..UT. smIIl31.!I.!lO J.sn SI-IIA tl-IIA H-lIA ZI-IIA n-IIA O1-IIA 6-IIA 8-IIA L-IIA 9-IIA S-IIA t-IIA €-IIA Z-IIA l-IIA O1-IA 6-IA 8-IA L-IA 9-IA S-IA 1tIA €-IA Z-IA l-IA I-AI 1tIll €-Ill Z-Ill I-III Z-I 1-1 'ON LIST OF PHOTOGRAPHS NO. DESCRIPTION PAGE 1 Denton Creek - Upstream of Denton Tap Road in Andrew Brown Park . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cover 2 Stream G4 - The Duck Pond Greenbelt Park ................. ii 3 Stream G6 - Moore Road . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv 4 Elm Fork of the Trinity River at Sandy Lake Road . . . . . . . . . . . . . vi r- 5 Stream G2 South of Bethel School Road .................... xviii 6 Stream G 1 - Downstream Face of Bethel Road . . . . . . . . . . . . . . . . Chapter I 7 Elm Fork of the Trinity River - Wellington Apartments Flooding, May 1990 Chapter IV 8 Parkwood Channel Upstream of Moore Road . . . . . . . . . . . . . . . .. Chapter V 9 Cottonwood Branch Flooding - Behind 250 Winding Hollow Ln. .. VI-27 10 Stream G1 - Upstream of Bethel School Road ................ VI-40 11 Grapevine Creek Downstream of Denton Tap Road Erosion, June 1990 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chapter VIII 12 Denton Creek/Cottonwood Branch - Andrew Brown Park Flooding, May 1990 .................... Chapter IX xv lAX ZJ m~llS IJ m~llS q:JUlUg POOMUOllO;) 10 m~llS ){~lJ U01U~0 ){lOd UJ[3 9D m~llS !;D m~llS VPD m~llS PD m~llS ~D m~llS VZD m~llS ZD m~llS 1 D m~llS ){~lJ ~lI!^~d-elD ){~lJ ~lI!^~d-elD 91-!; ~l-eld !;1-!; ~l-eld Pl-!; ~l-eld El-!; ~l-eld ZI-!; ~l-eld n-!; ~l-eld 01-!; ~l-eld 6-!; ~l-eld 8-!; ~l-eld L-!; ~l-eld 9-!; ~l-eld !;-!; ~l-eld P-!; ~l-eld ~-!; ~l-eld Z-!; ~l-eld 1-!; ~l-eId ~IYOld POOH l~ .kOOl pu-e -Z q:JU-elg pOOMuollO;) ZJ m~llS pu-e 'IJ m~llS 'q:JU-elg pOOMUOllO;) 10 m~llS pu-e 'IJ m~llS 'q:JU-elg pOOMUOllO;) 10 m~llS pu-e ){~lJ U01U~0 q:JU-elg POOMuollO;) ~u~nlJUo;) q:JU-elg POOMUOllO;) pu-e ){~lJ U01U~0 ){~lJ U01U~0 l~^rn Al!UJ.I.L ~ql JO ){lOd UJ[3 ){~~lJ ~lI!^~d-elD 1 D m~llS pu-e ){~lJ ~lI!^~d-elD 9D m~llS pu-e 'vPD pu-e PD m~llS '~D m~llS 'vZD pu-e ZD m-e~llS PD m-e~llS pu-e '~D m~llS 'ZD m~llS 'ID m~llS '){~lJ ~lI!^~d-elD 9D m~llS pu-e !;D m~llS 9D m~llS pu-e !;D ~llS '){~lJ ~lI!^~d-elD ){~lJ ~lI!^~d-elD x~PU} ~l-eld ~l-eld uon-epunU} pooH l~A-OOlloJ pu~~;}'"} 8-P ~l-eId L -V ~l-eld 9-P ~l-eld !;-P ~l-eld P-P ~l-eld ~-P ~l-eId Z-P ~l-eld I-P ~l-eld L-~ ~l-eld 9-~ ~l-eld !;-~ ~l-eId P-~ ~l-eId ~-~ ~l-eld Z-~ ~l-eId 1-~ ~l-eld O-~ ~l-eld ~ ~l-eld ~l-eld l!m!'1 UO!l-epunuI pooH l~A-OOl d-eW ~Sfl pUlrl pu-e ~lV ~~-eU!-elO uon-e:JO'] l~rOld JI XI<IN3ddV NI SaLVld JIO .Lsn Z ~l-eld 1 ~l-eld ACKNOWLEDGEMENTS r--"' ,j Albert H. Halff Associates, Inc. wishes to acknowledge the valuable assistance of the many organizations and individuals who have assisted in the preparation of this report. We wish to express our gratitude to those who have contributed their time and effort to this study, especially those mentioned below. r ,--. I ' .~. ",,} ,--.. i I Mr. Alan D. Ratliff, City Manager and Mr. Steven G. Goram, Director of Public Worlcs, Mr. Gary Sieb, Director of Planning and Community Services, Mrs. M. Shohre Daneshmand, Acting City Engineer, and Mr. Per Birdsall, Mr. Ray Gonzales, and Mr. Rick Wieland of the City of Coppell Public Works Department, who have provided invaluable assistance in the development and completion of this report. Members of the City Council of the City of Coppell, especially Mr. Ron Robertson and Mr. Peyton Weaver, also provided guidance and leadership throughout the preparation of this study. lJ ,..., l ~ The employees of Halff Associates who have worked most closely on this project include: Mr. Walter Skipwith, Ms. Jean Hansen, Mr. Thomas Guillory, Mr. Larry Trotter, Mr. Richard Westsmith, Mr. James T~ Spillman, Ms. Tamara Palmer, Mr. Timothy Spiars, Mrs. Susie Nevitt, Mr. Isaac Williams, and Mrs. Con stanza Andreescu. r LJ l' I , l. r I l I Halff Associates deeply appreciates the dedicated efforts of all the groups and individuals who have helped to perform this study. c C G o o rl .J xvii ABSTRACT In the City of Coppell the Elm Fork of the Trinity River and its tributary flood plains encompass approximately 2000 acres of land. These stream channels and flood plains provide the only scenic relief in an area typified by flat farm and grass lands.. Formed by centuries of storm water conveyance, these flood plain areas contain a wealth of scenic and environmental assets making adjacent land areas highly prized and desirable locations for all types of development. This same pattern of flooding which created the rich variety of vegetation and wildlife habitat can also threaten the users of the flood plain and adjoining developed land. The urbanization of Coppell, which is one of the fastest growing communities in the Dallas/Fort Worth area, is causing increases in storm water runoff. As a result, the historic flooding and erosion patterns are exceeded, posing a hazard to life and property and damaging the fragile ecosystems along the natural streams of the area. Consequently, a city-wide storm water management plan is necessary to mitigate the flood hazards and damages that urbanization can bring to a community such as Coppell. During the past five years the City of Coppell has received numerous drainage complaints in both the established residential subdivisions and these rapidly developing areas. To compile and review these complaints the city council of Coppell appointed a Natural Drainage Subcommittee in 1989 made up of citizens and staff. This committee prepared a comprehensive list of the problem areas and made recommendations as to the severity and priority of each problem. In recognition of these problems, the City of Coppell authorized Albert H. Halff Associates, Inc. to proceed with a City-Wide Storm Water Management Study in March, 1990. The study consists of the investigation into the designated 100-year flood plain of the Elm Fork of the Trinity River, Grapevine Creek, Denton Creek, Cottonwood Branch, and nine unnamed tributaries of these streams. Analyses of local drainage problems compiled from citizen complaints are also included. City-wide storm water management alternatives are evaluated to help prevent future flooding problems in the existing and developing neighborhoods of Coppell. The study found that the City of Coppell's flood plain management efforts along its tributaries have been generally successful in keeping houses out of the 100-year flood plain. The inventory of flooding sites shows only 15 occupied residential structures and one apartment complex inundated by the 100-year design flood along the 25 miles of streams studied. All but five of the individual residences are in older areas of town which may be expected to redevelop. Twenty-four streets on eleven streams are also flooded.. In addition, stream bank and channel erosion is occurring as urbanization increases flood flows and the natural drainage paths are altered. The recommendations included in this report to alleviate or control these stream flooding and erosion problems are shown on Table 1. These flood control recommendations remove nine of the fifteen residences from the 100-year flood plain for a fully developed watershed. The residences on Deforest Road along the Denton Creek channel, one residence on Cottonwood Branch at the State Road crossing and two residences on Stream G 1 remain in the design flood plain. These are all in areas which are expected to redevelop. The Wellington Apartments also remain in the Elm Fork of the Trinity River flood plain. It is recommended that the City of Coppell request that the apartment flooding be investigated along with a detailed study of the Riverchase area as part of the Corps of Engineers Feasibility Phase Study of the Trinity River. Additional information on each flooding site can be found in Chapter VI of this report. xix xx 'ITA 19ldl1q:J IT! punOJ gq UR~ Sgl!S gSgql JO q~l1g UO UOpl1WlOJU! fBuoPWPV 'I gyql1.L IT! 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I wv~s I SNOI.LVON3WWO;)3lI 30llS NOISOH3 ONV DNIOOO'l!l WV3lI.LS .110 AHVWWnS 13'1HV.L TABLE 2 SUMMARY OF LOCAL DRAINAGE PROBLEM SITE RECOMMENDATIONS I SITE LOCATION I ESTIMATED COST I Freeport Parkway near Southwestern Boulevard $ 280,0001,2 Bullock and Howell Streets $ 37,000 Brooks Lane/HWlterwood -- Stage I $ 162,000 -- Stage IT $ 63,000 Cozby and Kaye Streets -- Cozby Street $ 17,lXllf -- Kaye Street (North) $ 102,OOOZ - Kaye Street (South) $ lll,OOOZ Golden Triangle Mobile Home Park $ 90,0002 CononwoodlSummer Place $ 42,000 Whispering Hills Drive at Sandy Lake Road $ 56,000 Shady Dale Lane $ 39,000 Swan Drive $ 30,000 Hawk Lane $ 26,000 Sandy Knoll Drive/Shadowcrest Lane -- Sandy KnolllShadowcrest - Stage I $ 22,000 -- Sandy Knoll/Woodhurst Pavement $ 19,000 -- Sandy KnolllShadowcrest - Stage IT $ 60,000 Parkwood Channel $ 405,000 Moore Road/Samuel Boulevard -- Samuel Boulevard/Meadowridge Condo. Flooding $ 69,lXllf -- Moore Road - Interim Pipe & Inlet $ 28,000 - Permanent Drainage Imp. $ 249,000 Meadows Subdivision -- Stage I $ 45,000 -- Stage IT $ 150,000 MacArthur Boulevard/Sandy Lake Road $ 12,000 Woodridge Channel -- Interim Solution $ 9,000 - Ultimate Solution $ 530,000 Mapleleaf Lane - Stage I $ 49,000 -- Stage IT $ 28,000 Fieldcrest Loop $ 61 ,25Q4l TOTAL LOCAL DRAINAGE PROBLEM SITE RECOMMENDATIONS $ 2,791,250 1 Recommendation not made. Less expensive alternative shown for comparison. 2 Potential cost sharing with developer and/or property owner. 3 Recommended alternative and estimated cost from report by Ginn, Inc., July 14, 1989. Many of the drainage complaints not included in the sites shown on Table 2 were similar and could be characterized as "poor drainage". Site visits revealed weed and silt choked drainage ditches and channels. Formulation of an expanded maintenance program which may require additional city personnel and/or equipment is recommended. Other complaints throughout the city concern standing water in the streets. It was determined that the majority of these problem sites stem from differential movement of the pavement due to the underlying expansive clay soils. A regular street maintenance program is also recommended. XXI nxx .f: ~lqB.L lI! Uh\oqs S! SUO!lUpU~WUIO~~l ~qSl~lUh\ lUl~u~~ pun ~P!h\-lI!suq ~ql JO h.mUIWnS V .IA l~lduq;) U! 6-IA ~mH uo Uh\oqs s! unld s!l{.L .1U~IlllIBd~Q uO!lu~n~~ pun S~lUd ~ql ql!h\ AI~SOI~ ~lUUWloo~ oSlU SUh\ Snull ~~q pun ~~ IUUO!lWPU pUU SAUh\~lUd 'uo!l!s!nb:lu 11~Ug~U~ ~Uwnpu! 'uvlcl tJ:)vdS uadO ansodwo:J ~q.L .SlU~IlllIBd~p g.ry pUU ~U!uunld 'uo!l~~dsll! ~uWnnq '~:lunU1J 'S~lOh\ ~nqnd ~ql wOlJ P~l!~HOS oSlU SUh\ lndUJ .SlgUh\O Au~dOld lUnp!AWU! ql!h\ s~u!l~~m lUlgA~S pUU ~ll!lU~q ~Hqnd U q~nOll{l ~l!~HOS SUh\ lndu! 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L..: f1 i I l "" ri Lf r-" ! L j' I I I '...~ 0, I , o o fl u o r I i '-. n LI o n o 11 L.- TABLE 3 SUMMARY OF BASIN. WIDE AND GENERAL WATERSHED RECOMMENDATIONS I RECOMMENDA nON I ESTIMATED COST1 I Valley Storage Preservation - Parallel Parkways $ 2,700,000 Greenbeh Preservation/Open Space Acquisition (286 acres) -- Trail System Extension $ 880,000 General Watershed Recommendations . Passive Flood Warning Systems $ 26.000 . Monumentation 2 . ConslJUction Site Erosion Control -. . Review of Drainage ConslJUction Plans -- . Creek Inspection - . Urban Storm Water Permits -- a. Drainage Data Base Not Estimated b. Base Maps. Topography Not Estimated c. Sampling/Gaging - Interim $ 4,000 . Finished Floor Certification - . Flood Plain Ordinance Revisions - . Initiate Regular Ditch Maintenance Program _. . Initiate Regular Street Maintenance Program - I Estimated Costs are total conSlJUction costs. City, developer or private participation not estimated. 2 Provided to City Staff separately. The [mal recommended City-Wide Storm Water Management Plan is the culmination of all these efforts. This plan was approved by the Coppell City Council in January of 1991 and is estimated to cost $11,965,250, including structural flood control and drainage system improvements as well as basin-wide and general watershed recommendations. The citizens of Coppell approved $800,000 in drainage improvements in a 1990 bond package. The individual recommendations were evaluated based on the severity of the problem, public safety, property damage, danger to existing structures and height, velocity and duration of flooding. This evaluation in conjunction with the approved bond funds was used to develop a six phase suggested implementation plan which is included in Chapter VIll of this report. Phases 1 and 2 correlate approximately to funds available in the existing bond program. Additional funding will be required to complete subsequent phases of the proposed improvements. Several of the flood control projects could also be funded through joint efforts with individual property owners, developers or other entities. Other funding sources such as municipal drainage utility districts and public improvement districts are also discussed in Chapter Vlli. Implementation of this City-Wide Storm Water Management Plan will help to control existing flooding and erosion problems and reduce the threat of increased flooding due to man's activities. The flood plains of Coppell, a valuable natural resource, will also be preserved for future generations. XXlll I. INTRODUCTION The Coppell area was first settled in 1832 and has known the names of Grapevine Springs and Gibbs. The current name of Coppell was established around 1890. The City now occupies a unique and enviable position. It is bordered by Interstate Highway 635 on the southwest, State Highway 121 on the north, and the Dallas-Fort Worth International Airport on the west. This strategic location within the Dallas-Fort Worth metroplex places the City of Coppell in an active development rone. In fact, the city is already experiencing rapid development. In 1980, the recorded population was only 3,826 persons. (1) This number increased to more than 10,500 by 1986(2) and according to the recently released 1990 census data is currently 16,881.'3) The City of Coppell contains three major waterways which ultimately drain into the Elm Fork of the Trinity River along the eastern corporate limits. Formed by centuries of flood water erosion, Grapevine Creek, Cottonwood Branch, Denton Creek, and the Elm Fork flood plains contain a wealth of scenic and environmental assets. The adjacent land areas have become highly prized and desirable locations for all types of development. However, the same flood waters that created the rich variety of vegetation and wildlife habitat, threaten both existing and future developments. Continued development along the flood plain and in the city increases storm water runoff, causing larger and more frequent floods, which are the most fatal of all natural hazards in the United States. Flooding accounts for 163 deaths across the U.S. in a normal year, while tornadoes and lightning strikes are responsible for 98 and 97 deaths, respectively. (4) In the Spring of 1989, flooding caused approximately 25 deaths and in excess of 12 million dollars in damages throughout North Texas. (S) Developments in and along the flood plains of Coppell also experienced flooding and drainage problems as a result of the 1989 floods. Realizing these problems, the City of Coppell commissioned this City- WuIe Storm Water Management Study to address drainage problems that might be caused by both historic and future floods. A Objectives of the Study The main objective of this study is to develop a comprehensive City-Wuie Storm Water Management Plan which will address existing drainage, flooding, and erosion problems and provide a master plan to control future flooding problems within the city. The study consists of investigations into the designated 100-year flood plain along Grapevine Creek, Cottonwood Branch, Denton Creek, the Elm Fork of the Trinity River and selected tributaries, as listed in Table 1-1 and shown on Figure 1-1. Investigations will also be made into local drainage problems as identified by the citizens and staff of the City of Coppell. Flooding sites will be inventoried and alternative solutions to these problems will be presented. A comprehensive storm water management plan will be developed which includes flooding and erosion mitigation measures, open space, parkway and recreation plans and general watershed recommendations. The objectives of the Coppell City- Wuie Storm Water Management Plan are: 1. To prevent loss of life; 2. To minimize property damage; 3. To minimize erosion and deposition; 4. To preserve open space; 5. To preserve animal and plant life; 6. To use the flood plain for water conveyance, transportation routes, and utility rights-of-way; 7. To provide recreational areas; 8. To put flood plain land to .its best and highest-priority use; 9. 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Ol suolJ;) ;)A!lgJ;)dooo lI! ;)lgdp!ugd Ol SlU;)P!S;)J gU!lS!JU;) Aq spooq1Oqqgpu ~qms 0.1 "01 TABLE 1-1 STREAMS IN THE COPPELL STORM WATER MANAGEMENT STUDY Stream Name Study Limits Length of Study Total (Feet) Drainage Area (Mi2) Grapevine Creek -4,000' Downstream of MacArthur Blvd. 30,400 14.1 to 1-635 Stream G 1 Grapevine Creek to Freeport Parkway 6,000 1.3 Stream G2 Grapevine Creek to Downstream of 3,300 0.4 Plantation Drive Stream G2A Stream G2 to Bethel School Road 1,000 0.1 Stream G3 Grapevine Creek to 450' Downstream of 1,400 0.1 Briarclove Lane Stream G4 Grapevine Creek to Willowsprings Drive 4,400 0.3 Stream G4A Stream G4 to 100' Downstream of Bethel 900 0.05 School Road Stream G5 Grapevine Creek to Bethel School Road 1,500 0.05 Stream G6 Grapevine Creek to Shadowcrest Lane 4,800 0.3 Elm Fork on the Grapevine Creek to Denton Creek 11,100 2459.01 Trinity River Denton Creek Elm Fork to S.H. 121 37,200 719.02 Stream D1 Denton Creek to 1,000' Upstream of 4,200 0.5 Coppell Road Cottonwood Branch Denton Creek to 3,500' Upstream of 22,700 7.1 Royal Lane Stream C1 Cottonwood Branch to 300' Upstream of 1,600 0.2 State Road Stream C2 Cottonwood Branch to 400' Downstream 1,500 0.1 of Ruby Road TOTAL LENGTH OF STREAMS STUDIED 25.0 mi. ---- 1 D.A calculated at Carrollton Dam 2 This D.A includes Grapevine Lake which has a D.A of 695 mi2. 1-3 Ta: uO!l:Y.)S 'IA J~ldRqJ Y ~lJS 'IIA J~ldRqJ o UO!l:Y.)S 'IIA J~ldRqJ f ~lJS 'IIA J~ldRqJ '1 ~lJS 'IIA J~ldRqJ '1 ~lJS 'IIA J~ldRqJ 'zra: uOJl:Y.)S 'IA J~ldRq;) '6'a: uOJl:Y.)S 'IA J~ldRq;) 'L'a: UO!l~ 'IA J~.dRq;) 'ca: uO!l:Y.)S 'IA J~ldRq;) Ta: uO!l:Y.)S 'IA J~ldRq;) 'ca: UO!l:Y.)S 'IA J~ldRq;) Ta: uOJl:Y.)S 'IA J~ldRq;) G ~lJS 'IIA J~ldRq;) o UO!l:Y.)S 'IIA J~ldRq;) G ~lJS 'IIA J~ldRq;) 'p'a: UO!l:Y.)S 'IA J~ldRq;) 'L'a: uO!l:Y.)S 'IA J~ldRq;) W ~lJS 'IIA J~ldRq;) o UO!l:Y.)S 'IIA J~ldRqJ ;) ~l!S 'IIA J~ldRq;) 'M UO!l:Y.)S 'IIA J~ldRq;) )I ~l!S 'IIA J~ldRq;) 'Ira: UO!l:Y.)S 'IA J~ldRq;) o ~l!S 'IIA J~ldRq;) W ~l!S 'IIA J~ldRq;) 'M UO!l:Y.)S 'IIA J~ldRq;) f ~l!S 'IIA J~ldRq;) 3 ~l!S 'IIA J~ldRq;) a: ;ms 'IIA J~ldRq;) 'M uO!l:Y.)S 'IIA J~ldRq;) H ~lJS 'IIA J~ldRq;) 'M uO!l:Y.)S 'IIA J~ldRq;) 'z'a: 'IA J~ldRq;) N ~l!S 'IIA J~ldRq;) W ~l!S 'IIA J~ldRq;) W ~l!S 'IIA J~ldRq;) d ~l!S 'IIA J~ldRq;) 'z'a: UO!l:Y.)S 'IA J~ldRq;) d ~l!S 'IIA J~ldRq;) o ~l!S 'IIA J~ldRq;) 'Z'S UOH:Y.)S 'IIA J~ldRq;) f ~l!S 'IIA J~ldRq;) '1 ~l!S 'IIA J~ldRq;) 'Z'S UOH:Y.)S 'IIA J~ldRq;) 3;)N3'M3d3'M AGf1..LS r-I gUJPOOld [e:)0'] gUJPOOld 1~J1S gUJPOOld 1~J1S € 'oN OSJV ~S gUJPOOld 1~J1S AlpRdR;) AlpRdR;) ~gRUJRJG 1;) m~J1S ';r.)URU~lUJRW )[~J;) U01U~G qlloN '90 m~llS 90 }O ..umnq!lllIR:>O'] )[~J;) ~1IJ^~dRJO 90 m~llS )[~J;) ~1IJ^~dRJO ~JnlJnJlselJUI ~JnlJnJlselJUI (a 'ON ~S) IR:>O'] PO pUR €O sm~J1S 90 m~J1S (gUJPOOld 1~J1S) IR:>O'] ~JnlJnJlselJUI (Z€ 'oN ~S) ~JnlJnJlselJUI ~JnlJnJlselJUI ~JnlJnJlselJUI qJURJa: POOMUOUO;) ;r.)URU~lUJRWI~JnlJnJlselJUI (6 'ON ~S) IR:>O'] ;r.)URU~lUJRWlIR:>O'] ~JnlJnJlselJUIlIR:>O'] ~JnlJnJlselJUI ~JnlJnJlselJUI ~JnlJnJlselJUI IR:>O'] IR:>O'] ~JnlJnJlselJUI ~JnlJnJlselJUI ~JntJnJlselJUl (OZ 'ON ~S) ~JntJnJlselJUI ~JntJnJlselJUI 1 0 m~J1S ~JntJnJlselJUI I~uuRq;) IR:>O'] m~lsAs ~gRUJRJG pJRpURlsqns - IR:>O'] ~JnlJnJlselJUl )[~J;) U01U~G }O ..uRlnq!lJ, ~!pnlSUfl ~JnlJnJlselJUI W3'1S:0'Md dO 3cLUlWV3'MJ.S pRO'M )[~JJ MOp~W Lp ARA\)[JRd 1l0d~Jd UO ~xell~^O Sl~IUI 9t ..ulU3 SA\OP~W pURNgrn !;p UOH:y')Sl~lUll~J:>MOpRqSlIlOU)! 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(f; i rr .I I \ ,--:"y,--' I I ~ i!. / r<l f' -. -I- . ______J_-~) ~~ . \&" \.l ! --, i I / , ~-~ ~ ,\ I -_/ ~ \., .. :~~~ ;:::::> \- --.: -; h / 1.__ · Ii" ". ~A/ . c", (-AI '\ 1 : I' I 90000 I : I o z w (!) ~ UJ ~ 0 ~ 8en ffl!J en Li~..J~~ ~..J t-~~~~ ~~ ~~:i~~ ~ 1il:i ~~5~~ 9 ~~ >- enD c~ ~ wa: CJ) CIJ I- ~ W u;:) "':I: Wm wo ....J _ W c: wa: C[: w en~ ua: w z ::::; I 0: W !;t I ...JI ..-~I-~ , q I~Z::) I d -a:WI- I WO~(/) Dc ~~~~.~- ~I CJ~~~ @~~~ z o ~ -' o 0: 0: ct U o ~ N ~ o m :;: "' .. .J ~ z ......a::$ ~ 0 '"'- -- ~-~ ~ e-r ....,. V> ct -' -' ct o ~:j' ...... II h I ~J lit 'I' -- ./0" .' 'j / 'j I / .~- ..J ~~ 00: .. ~ C. Description of the Watershed The City of Coppell is located in the northwest comer of Dallas County. The northern boundary of the city extends into Denton County to the Lewisville municipal boundary. The Dallasffarrant County line forms the western limits of the city. Other surrounding municipalities include Dallas, Irving, Grapevine, Flower Mound and Carrollton. The city contains approximately 15 square miles of land and includes portions of the drainage areas of Grapevine Creek, Denton Creek, Cottonwood Branch and the Elm Fork of the Trinity River. Plate 1, Appendix F, the Project Location Map, shows the general location of the City of Coppell in relation to the Dallas-Fort Worth metroplex. The Elm Fork of the Trinity River flows in a southerly direction forming the eastern city limits of Coppell from downstream ofthe Carrollton Dam at Sandy Lake Road to its confluence with Grapevine Creek. This reach of the Elm Fork is approximately 2 river miles long with a total drainage area at Grapevine Creek of almost 2,500 square miles. Grapevine Creek and Denton Creek, two major tributaries of the Elm Fork, form portions of the southern and northeastern boundaries of the city, respectively. At its confluence with the Elm Fork Grapevine Creek has a total drainage area of fourteen square miles, 6.3 square miles of which are located within the City of Coppell. Also included in the Grapevine Creek watershed is the 2.7 square mile drainage area of the North Lake Generating Plant cooling lake. This plant, operated by Texas Utilities Electric Company, is located immediately south of Belt Line Road and is accessible to the citizens of Coppell for recreational uses. Denton Creek encompasses a total drainage area of 719 square miles which includes the Grapevine Lake drainage area of 695 square miles. The remaining 24 square mile drainage area includes portions of the Cities of Grapevine, Lewisville, Carrollton, and Coppell. Also included is the 7 square mile watershed area draining to Cottonwood Branch, a major tributary of Denton Creek. Numerous small tributaries of these major creeks also traverse the City of Coppell providing drainageways for existing and future developments within the city. As these major streams and their tributaries meander through the City of Coppell, they bisect some of the most desirable development locations in the metroplex. Along Grapevine Creek much of this land has already been developed, primarily within the last ten years, but large tracts still remain, especially along Cottonwood Branch. Rapid development of such areas is often accompanied by increased flood flows resulting from urbanization and reclamation within the flood plain. Land use plans to convert most of the remaining vacant and agricultural acreage to residential, commercial, and industrial development already exist for Coppell and its surrounding cities. This City-Wule Storm Water Management Study will complement these existing land use studies, while serving to minimize problems from future flood events. D. History of Flooding 1. Hydrologic Instrumentation There are two active United States Geological Survey (USGS) stream gages within the study area. The gage on Denton Creek is located at State Highway 121 on the left bank of the downstream side of the bridge. This gage has been active since October of 1947. Since July of 1952 flow at this gage has been regulated by Grapevine Lake. The other stream gage is located on the Elm Fork of the Trinity River at Sandy Lake Road approximately 40 feet upstream of the Carrollton Dam. This gage was activated in 1907. The flow at this gage is largely regulated by Lewisville Lake (November 1954) and by Grapevine Lake on Denton Creek. The City of Dallas diverts water from the pool at this gage and from the river 14 miles downstream for municipal use. A water treatment plan returns water to the river south of this station. Texas Utilities Electric Company also diverts water from this pool into North Lake to supply cooling water for their electric plant. 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J(~J;) UOlU~a 8uOI-e poou~p~dx~ s-eM poog JOr-eUl -e 'SlU~P!~J 1-e:l01 Ol 81I!pJO:Y.>V SPOOH :>pOlS!H 'Z 's'o's'n ~ql Aq {Y.)qs!lQnd SUon-e^~I~ pu-e ~8J-eq:lS!P - ~8-e8 UI~JlS pJo:Y.)J snonunuO;) t p-eo'M ~J(lr] APU-eS uo ~8ppq JO ~P!S UI~JlSUA\Op J(U-eq lJ~Vsmc~~ lU~~Jd-L061 'UOlrrOJJ'e;) J~U J~^rn Al!1J!l~ J(JOd UIl3 OOSSS080 lZl HS uo ~8ppq JO lU~~Jd-Lt61 J~!d lJ~Vsmc~~ '~U!^~d-eJO J~U J(~J;) UOlU~a OOOSS080 pJo:Y.)'M JO POP~d UOn-e:lOJl~UI-eN Uonms J~qUlnN Uonms sosn VIDIV AUilJ.S IDLL NI lSNOLLVJ.S ~NI~V~ WVIDlJ.S NIsva: 1I~ AJ.INnu f-I3'1UVJ. numbers of livestock out of the flood plain.(10) This flooding continued into June 1989 with the period from June 1-14 characterized as a period during which it rained somewhere within the Upper Trinity River Basin everyday. Both Lake Lewisville and Grapevine Lake recorded peak elevations above the crest of their uncontrolled spillways. The peak flow over the spillway on Grapevine Lake, June 14, 1989 was recorded at 4,525 cis, or 2,525 cfs greater than the Denton Creek channel capacity. (11) In the City of Coppell, numerous drainage complaints were received from citizens. Major flooding occurred along Sandy Lake Road approaching the Elm Fork of the Trinity River and in Andrew Brown Park at Denton Tap Road and Cottonwood Branch. This flooding, along with the increasing development along the floodplain, led to the commission of this City-WuJe Storm Water Management Study. During the course of this storm water management study, in May and June of 1990 severe flooding again hit the metroplex area. For the second year in a row residents of the Trinity basin paid a heavy price in terms of loss of life and property caused by flooding throughout the basin. The first five months of 1990 were the second wettest on record for North Central Texas with 29.21 inches of rain recorded as compared to the normal amount of 13.9 inches for this same time period. (12) Additional heavy rainfall on May 1-4 caused even greater flooding than in 1989 with a flow of 8,040 cfs recorded on May 4, 1990 over the uncontrolled spillway at Grapevine Lake. (13) In Coppell, Sandy Lake Road was closed again and water backed up into Riverchase Golf Course making the clubhouse an island. The east end of the Wellington Place Apartment complex on MacArthur Boulevard near the golf course had water in cars and apartments. (14) Figure 1-2 is an aerial photograph taken May 5, 1990 showing the flooding along the Elm Fork of the Trinity River in the Coppell area. Early estimates from the Corps of Engineers put this flow in the 25 to 50 year return period. 3. Storm Water Management Before 1990 Grapevine Dam on Denton Creek and Lewisville and Ray Roberts Dams on the Elm Fork of the Trinity River are the major flood control projects affecting the study area. These reservoirs, providing flood control, water supply, and recreation, were completed in 1952, 1954 and 1987, respectively. Denton Creek and the Elm Fork of the Trinity River were studied in conjunction with the planning for Grapevine and Lewisville Lakes in a report entitled House of Representative Document Number 403 (HD No. 403), "Trinity River and Tributaries, Texas" published in October 1941.(15) Ray Roberts Lake is part of the plan of improvements recommended in House of Representatives Document Number 276 (HD no. 276) "Trinity River and Tributaries" published in August 1965.(16) Pertinent information on all three of these lakes is given in Table 1_4.(17) TABLE 1-4 PERTINENT DATA ON CORPS LAKES IN THE UPPER TRINIlY RIVER STUDY AREA Name Location Drainage Length Max Spillway Level Pool Data Volume Area of Height Elevation (ac-ft) (sq.mi.) Dam (ft) (ft NGVD) (ft) Grapevine River Mile (R.M.) 11.7 695 12850 137 500' Ogee Conservation 535 181,100 (1952) on Denton Creek, trib uncontrolled Flood Control 560 425,500 of Elm Fork Max. Design 581 758,800 Lewisville R.M. 30.0 on Elm Fork 1660 32888 125 500' Ogee Conservation 522 618,400 (1954) Trinity uncontrolled Flood Control Max. 532 954,500 Design 549.2 1,804,300 Ray Roberts R.M. 60.0 on Elm Fork 692 15250 131 100' Broad Conservation 632.5 799,600 (1987) of the Trinity River Crested Flood Control Max. 640.5 1,064,600 uncontrolled Design 658.8 1,931,900 1-8 066 ~ '9 AVW - ~NI(]OO'.:I ~-I 3I::1n~l.:I The City of Coppell also joined the Federal Emergency Management Program on June 11, 1975. The original Flood Insurance Study (PIS) for the City of Coppell was published in August 1980. In February of 1984 a FIS update was published showing profiles for the 10-, 50-, 100-, and 500-year floods, delineating the 100- and 500-year floods and establishing a floodway encroachment limit for the Elm Fork, Denton Creek, Grapevine Creek and Cottonwood Branch. (1S) Flood insurance studies for the adjacent communities of Carrollton, Grapevine, and Irving, Texas were prepared concurrently with this update and are in total agreement. The Dallas County PIS was prepared before levee improvement data along the Elm Fork of Trinity River was available and does not match these studies. In November 1976, a report entitled Partial Hydrologic and Hydraulic Data for Flood Plain Delineation, Grapevine Creek, City of Coppell, Texas, was published.(19) This report covered the reach of Grapevine Creek between Moore Road and Denton Tap Road. The 100-year frequency flood elevations and discharges were developed based on a fully developed watershed and, as would be expected, are higher than those developed for the Coppell Flood Insurance Study. In addition numerous other individual hydraulic studies have been published during the past ten years for developments such as Riverchase and Vista Ridge adjacent to the flood plain. Rapid development along the streams of Coppell led to the update of the 1984 Flood Insurance Study in 1989 and 1990. The updated study is scheduled for publication in 1991. In conjunction with this Flood Insurance Study update, discharges based on fully developed land use were calculated by Kimley-Horn and Associates, InC.(20) To extend this study and develop a coordinated Master Plan for storm water management within the city, Coppell commissioned Albert H. Halff Associates, Inc. to prepare this City- WuIe Storm Water Management Plan in March of 1990. 4. Flood Frequency Analysis The 100-year flood discharges presented in this study have been calculated using the 100-year frequency rainfall data published by the u.S. Weather Bureau. (21,22) In computing the 100-year flood discharges, this study has applied unit hydrograph methodology using the Corps of Engineers, computer program HEC-1. (23) Flood discharges can also be determined by statistical analysis of historical flood records at stream gaging stations. This method is commonly referred to as flood frequency analysis. Two USGS stream gaging stations are located on the streams being delineated in this study. Recorded peak flood discharges are published for these gaging stations (See part D.1 of this chapter). A flood frequency analysis can not be performed for the minor tributaries analyzed in this study, due to the lack of recorded gage data. r- The flood discharges for the major streams in this study were developed by Kimley-Horn and Associates, Inc. This study states that data from the existing stream gages and the regulated flows of Grapevine and Lewisville Lakes were evaluated. (24) The Corps of Engineers, HEC-1 computer program was also used for that study. Flood frequency analysis was not used primarily because of the significant changes in the watersheds in and around the City of Coppell. It is increasingly difficult to find watersheds in which the flow regime has not been altered by man's activity. Man's activities which can change flow conditions include urbanization, channelization, levees, the construction of reservoirs, diversions and alteration of cover conditions. As discussed previously, three major reservoirs have been constructed within the watersheds of the City of Coppell. Numerous channelization and land reclamation projects have also altered the homogeneity of the stream channels and flood plains. Flood frequency analysis is often not reliable in such rapidly developing watersheds. 1-10 n-I '.LIwn SIHL a33:JX3 S3W1L3WO'S A.VW SA\O'ld aO'O'ld GNV 'aO'O'ld W3A-0013HL WO',&! A.L3dVS 0'.1 a3.LIWn SI A.CIf1LS SIHL NI NO'llJ3.LOMd '1V:JllJ~d.1VHJ.. aNIW NI wg8: amO'HS SN3ZI.LI:J ''llil:J:JO' A.VW GO'O'ld W3A-OOl 3HL NVHJ.. 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FLOODING INFORMATION r- A flood occurs when the runoff caused by precipitation, rainfall or melting snow, is too great to be confined in normal water channels. Many factors affect the quantity of runoff produced by precipitation. The climatic and physiographic characteristics of the watershed and its flood plain are analyzed in order to establish a specific flood's flow rate and water surface elevations. This chapter contains an inventory of the climatic and physiographic factors that influence flooding in Coppell. The inventory is limited to factors that can be assigned a quantitative value indicative of conditions in the study area. A detailed discussion of all these factors appears in Hydrology and Hydraulics of Flood Plain Studies. (1) This chapter also includes the flood plain information developed in this study. A Climatic Factors Coppell lies in a region of temperate mean climatological conditions and experiences occasional extremes of temperature and rainfall of relatively short duration. Climatological data available from the National Oceanic and Atmospheric Administration for Dallas-Fort Worth, Texas are indicative of the conditions prevailing over the watershed. The mean relative humidity is 65 percent and the average temperature is 66.0 degrees. The record temperature extremes range from a maximum of 113 degrees Fahrenheit in June 1980 to a minimum of 4 degrees Fahrenheit in January 1964. The maximum monthly and 24-hour rainfalls are 14.18 inches in October 1981 and 5.91 inches in October 1959, respectively,<2) Coppell is approximately 250 miles inland from the Gulf of Mexico. Remnants of tropical storms generally occurring from August to October sometimes reach the Coppell area and have caused significant flooding. Intense thunderstorms usually occur in the spring and summer and are the most common cause of flooding in Coppell. However, these thunderstorms can and do occur at any time of the year. Snow seldom falls in significant amounts. in this area and is relatively unimportant as a source of moisture. 1. Frequency and Duration of Rainfall A design storm is characterized by its depth, duration, frequency and distribution. The point rainfall depths used in this study are shown in Table II-I and were taken from National Weather Services Publication Technical Paper No. 40.(3) This document provides accumulated point rainfall amounts for storm durations ranging from 30 minutes to 24 hours and frequencies ranging from 1 to 100 years. For one hour rainfall durations and smaller, point rainfall data was obtained from National Oceanic and Atmospheric Administration (NOAA) Technical Memorandum NWS Hydro-35.(4) TABLE II-I POINT RAINFALL DATA FOR COPPELL AREA (inches) FROM TP-40 Return O.5-Hr. I-Hr. 2-Hr. 3-Hr. 6-Hr. 12-Hr. 24-Hr. Period (Year) 2 1.51 1.90 2.20 2.50 2.95 3.45 4.00 100 3.40 4.25 5.15 5.70 6.90 8.30 9.60 II-I Z-I1 oMol~q Z-I1 ~Jqtl~ lI! UMOqS ~ltl pUtl ,!ooqPUtJH ~UJ.L;J;JUJ1iU'3 /tJuoptJN S:JS ~ql JO Z"P ~Jqtl~ lI! punoJ ~ltl q:)!QM 'bwv) suompuoo ~lnlS!OW IU~~IUtl JO Sf~A~1 ~lql ~uy~p A~~ oWlOIS tl OllOpd UOmpUOO ~lnlS!OW nos ~ql iJuWISStlP 10J ~nb!Ull~1 tl Jr.}dOI~A~p Stlq ~!^l~S uO!ltlAl~suO;) nos "sOn ~ql 'S!ql iJlI!Z1ffii~'M IJoUnl JO ~ltll pUtl ~wnlOA ~ql qloq uo ~D~ IUt!:)~!S tl ~Atlq 01 UMoIDf S! ~lnlS!OW nos IU~~IUV o~~q AtlW DOUnl l~l!P ~lOJ~q Jr.}lsntlqx~ ~q lsnw ltlql ~iJtllOIS l~ltlM-nOS ~ql pUtl 'UO!ltllodtlA~ 'UO!ld~l~lll! 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SllOd~l sno!^~ld lI! Jr.}sn uonnqpIS!p :)n~qluAs ~ql ltlql ~1t!:)!Pll! quoi\\. UOd lI! SJS ~ql ql!M SUOntlSl~^UOO pUtl ~u~PUOd~llO;) "~ltl Apnls ~qllnoqiJnolql Jr.}sn StlM UOntllnp W10IS lnoq ~AI~Ml ~ql (S)'ApnIS ~iJtlU!tllO l~IStlW lI~ddO;) JO hID sno!^~ld ~ql JO ~Stl:) ~qllIl "~iJltlq:)S!p )f~d l~qiJ!q ~ql Jr.}ltll~u~iJ uO!ltllnp WlOIS q:)!qM ~1IJWl~I~P 01 Jr.}ltlnltl^~ ~q lsnw SUOntllnp WlOIS Itll~^~S '~Iqtll IItlJ1l!tll S~fUO!SU~W!P S!Ql ql!i\\. "sqdtllilOlpAq pltlOq~ld pUtl AtlMmds k>u~iJl~w3 10J uonnqpIS!O IItlJU!tl'M :)n~qluAS (SJS) ~!^l~S UOntlAl~suO;) nos ~ql Stl 01 Jr.}ll~J~l ~Jqtll ntlJ1l!tll S~fUO!SU~W!P tl StlM ~!pmS n~ddO;) JO hID lopd lI! Jr.}sn uonnqpIS!p ~W!llltlJ1l!tll ~~ IItlJ1l!tl'M JO uonnqpIS!G ~W!~ oz TABLE ll-2 SEASONAL RAINFALL LIMITS FOR AMC TOTAL 5-DAY ANTECEDENT RAINFALL AMC Group Dormant Season (inches) Growing Season (inches) I Less than 0.5 Less than 1.4 II 0.5 to 1.1 1.4 to 2.1 III Over 1.1 Over 2.1 AMC-I describes the lowest runoff potential, since the watershed soils are dry. AMC-II describes the average moisture conditions, and AMC-III describes the highest runoff potential, where the watershed is practically saturated from antecedent rains. The antecedent moisture conditions can be estimated from the amount of rain that has fallen in the five preceding days by the use of Table 11-2, which gives the rainfall limits by season categories.(9) The 100-year flood runoff computations for this study are approximately equivalent to an antecedent moisture condition (AMC) of II. The effects of interception, evaporation, and transpiration have not been calculated individually for this study. The overall effect of these factors on flooding is encompassed by an initial loss of moisture which is subtracted from rainfall at the beginning of the storm and a uniform loss of moisture subtracted thereafter during the storm. The loss rates used in this study are shown in Table 11-3. B. Physiographic Factors 1. Basin Characteristics a. Geometric Factors The geometric properties of a basin include its length, width, slope, and drainage area within various reaches of the basin. These properties describe the basin's shape and influence the way in which storm runoff will flow past various points along the stream channel. For example, a basin that has a long, thin shape will generally produce smaller peak discharges at its outlet than will a basin which is short and wide. The same is true for a basin with gradual slopes, as compared to one whose slopes are relatively steep. Hydrology and Hydraulics of Flood Plain Studies prepared for the City of Dallas(lO) contains a complete discussion of these factors. This study includes the Elm Fork of the Trinity River, Denton Creek, and Grapevine Creek which are tributaries of the Elm Fork. Cottonwood Branch, a tributary of Denton Creek, is also included. Nine unnamed tributaries of Denton, Cottonwood, and Grapevine Creek are also included in the study. All streams located within the study area are shown on Plate 2 in Appendix F. 11-3 rn 1dooX'3 'U!Rld pooD pROlq R pUR 1U~!PRI~ ~lntRm R Sllq m~llS ~q1 'URm Aq ~l~lIRUn ~l~QA\ 'AtUnOJ SllrrRa l~MqUOU U! ~ln1~J 11r.J!sAqd 1URU!WOP ~q1 S! l~Arn At!U!l~ ~Ql JO JflOd UII3 ~U SlOl:>Rd 11r.J!sAqd ':> fTO W'O lnOHl~q:>UJ - ~lR'M UO!lRl1I!JUI 06'0 ~L'O ~q:>U! - SS<YJ IR!l!UJ PURS ARIJ k)U~nlr,)ld aOH.L:>IW WlI0.ilINIl UNV JI::>O'UI SaLW SSO'I f-n :I"UlV.L 'f:-n ~IQR~ U! 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Z ~lRld uo U~S ~q U1r.J ~!lmnq!ll ~!pnlS ~q1 }O At!SU~P pUR A:>u~nlr,).IJ ~U '~nm l~d l~} 9'96 01 ~nm l~d l~} ~'8Z mo.IJ ~gURl ~dOIS I~uuRq:> 11r.J!dAt 'Apn1S S!q1 U! ~pnpU! ~!lR1nq!l1 ~U!U ~qllOd 'm~llS l~ql!~ uo ~l1r.JOI Sl!OAl~~l IOllUOO POOD lOfRm OU ~lR ~l~U 'AI~^!l~d~l '~nm l~d l~} 9'n pUR L'vl}O ~dOIS ~q ~^Rq sm~llS ~~U '~I!m E'v S! q~U~I ApnlS S,q:>URlg POOMUOllOJ '~lR ApnlS ~q1 urql!A\ gUOI ~nm 8'~ S! Jf~lJ ~U!A~dRlD '~nm l~d l~} 9'1 }O ~dOIS pnm R Sllq q:>rqM m~llS S!Ql }O ~nm O'L ~pnpU! Apn1s S!U '~Jftr'J ~U!A~dRlD 'l!OAl~~l m~llsdn ~glRI R Aq ~rrOllUOO OSIR S! Jf~lJ U01U~a guoIR ~U!PooH '~nm ~mnbs 0991 mo.IJ JjOUnl IOl1UOO pUR Sl~~U3}0 SdlOJ AWly 's'n ~Ql Aq ~lRl~do ~lR Sl!OAl~~l ~~U 'J{lOd UII3 ~q1 ~UOIR gUIPOOD IOl1UOO '~Jftr'J Sll~qO'M AR'M pUR ~II!AS!A\:rJ 'Sl!OAl~~l IOl1UOO POOD lOfRm O^\L '~nm l~d l~J t'E lR 'PUW Al~^ S! ~dOIS I~UURq:> ~U '~nm rz S! Jf~lJ U01U~a q1!A\ ~u~nuuoo Sl! 01 Jf~lJ ~U!A~dRlD q1!A\ ~u~nuuoo Sl! mo.IJ JflOd UII3 ~q1}0 q~U~I I~uURq:> l~A!l ~U for Denton Creek, which is similar to the Elm Fork, tributaries are less mature having eroded the Blackland Prairie and East Cross Timbers soils. Both Grapevine Creek and Cottonwood Branch are young, fairly straight streams with incised channels eroded into the upland soils of Coppell. The watershed lies within the western part of the Gulf Coastal Plain. Throughout the watershed the topography consists of gently rolling to undulating hills interspersed with the narrow valleys of small streams. U. S. Geological Survey 7.5 minute quadrangle maps are available for all of the watersheds. The topographic information covering the channel and flood plains within the City of Coppell was obtained by photogrammetric methods from aerial photography flown in 1985. The portions of the watershed in Dallas and Denton Counties lie in the western fringe of the region known as the Blackland Prairie. The soils in this area fall into two broad categories, upland and alluvial. Upland soils are the product of the disintegration and weathering of underlying strata. Alluvial soils are those which occur as recent deposits in flood plains and old deposits upon river terraces. The basic soil groups in Coppell's watershed are identified in detail in Chapter III of this report. The projected land use within a watershed can be used to determine the ultimate flood plain of that stream for a given storm frequency. Land use influences both the amount of runoff and the peak flood discharge produced by a storm. Changes from rural to urban land use increase the impervious area of a watershed and decrease the area available for infiltration and interception. As a result, rainfall that otherwise would have entered the soil is added to the volume of storm runoff. Impervious coverage as used in this report is an estimate of the percentage of the basin covered with impervious material. Urbanization is the factor used in this study to describe the percentage of an area that has been developed and/or improved with channelization and/or a storm collection network. Urbanization and changes in impervious cover alter the peak flow characteristics. The fully developed land use classification scheme was compiled using Coppell's future land use plan as published in the Comprehensive Plan. Hydrologic calculations for the fully developed land use condition assumed that the entire watershed was completely developed in accordance with proposed land use plans. This condition was used to define flood plain limits and to identify potential flooding sites based on existing channel and flood plain conditions. A more detailed discussion of the land use within the City of Coppell is included in Chapter III. These land uses are shown on Plate 2 in Appendix F. 2. Channel and Flood Plain Characteristics a. Carrying Capacity . The carrying capacity of a stream may be established by obtaining the relationship between the depth of flow and discharge. The ability of a stream (Le., the channel and the flood plain) to carry a given discharge at a specified depth depends on several geometric and hydraulic variables that may differ from point to point in a stream. These variables are: (i) the cross-sectional area of the stream and flood plain and the shape of the waterway; (ii) the slope of the streambed; and (ill) the resistance to flow. L Cross Section The area and the shape of the waterway may be obtained by measuring a cross section of the stream. The shape of the waterway can be described by two quantities, the area (A) and the wetted perimeter (P). These two quantities may be combined into a single quantity (R), known as the hydraulic radius. The hydraulic radius is defined as: 11-5 9-II .SMOO J~lRM ~ql q:>!1lM J~AO OORpnS ~ql jO s~uqgnOJ ~ql Aq JY.}snR:> S! 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Sl:l;)fOJd UOnRmRI:l;)J ;)Idmgxg "lu;)mdol;)A~P IRnU;)P!~J pUR 'nRl~J 'OOYJO JOj JY.}WYRI:l;)J u~q SRq At!UP!^ ~l tq tqRld poog;)1f.L "~IRMS }fURqJ;)AO pUR ~A~I jO UO!l:lnJ1SUOO ~V jO lS!SUOO AIIR:>!dAt SUOnR:>y!pom ;)~1f.L .~n!^n:>R UOnRmRI:l;)J tqRld poog Aq JY.}y!pom u~q OSfR ~ARq tqRld poog }fJOd mlg ~ql jO SUO!l:l;)S lU1r.)yyug!S .tqRld poog ;)ql jO uo!uod R JY.}!dn:>:>o ;)ARq SflYPURIIRdpyunm pUR suonRJ;)do glJ!lI!lD I~AR~ pUR PURS 'AnR:>p01S!H "1I!Rld poog pROJq AI;)AnRI~J R pUR I~UURq:> IRJnlRU JY.}UY;)P-I1;)M R SRq J;)Affi At!U!l~ ;)ql jO }fJOd WIg ~llL "SURld mOl) Sf~pom ~ql OlU! JY.}lRJOWOOtq ;)J~M SfIY tqRld poog 'JY.}PnJ1SUOO l~A 10U lnq 'JY.}AOJddR pUR }f~J;) ;)u!^;)dRJO J;)AO pRO~ dR~ U01U~G SR q:>ns ~Jnl:>nJls M;)N "0661 ARW SR AIlU;)Y.)J SR ~JR ;)mos tq JY.}WJop~d ;)J~M sA;)AJnS JY.}lRpdn .S86I tq UMOg sOloqd IRp~R mOl) JY.}JRd;)Jd sdRm :>!1ldR~odOl pUR s,OL6I pym ;)ql tq gtqU1I!g~q p;)l:>npuoo sA~AJnS PI;)y mOl) JY.}UJWl;)l;)P ;)J;)M ~pl;)mQ;)g tqRld poog pUR I;)UURq;) .AJ1;)mQ;)g tqRld poog pUR I~UURq:> jO ~Jn~m R SR SUO!lRln:>lR:> :>nnRJpAq tq JY.}sn S! J~l;)mRJRd S!llL d = ~ V Paved surfaces such as concrete lined channels, exhibit relatively low resistance to flow. Certain vegetal-covered surfaces, such as heavily overgrown flood plains, may exhibit considerably higher resistance. An increase of frictional resistance tends to reduce the velocity of flow. According to the principle of continuity (Q = A1V1 = AzVz), if the velocity decreases then the area of flow must increase in order to maintain the discharge (Q). This increase in area is manifested by an increase in depth of flow in the channel or flood plain. Manyvariables have been proposed to measure the frictional resistance. One commonly used is an empirical variable called Manning's roughness coefficient, On". A typical On" value for a stream channel is 0.035. In Coppell, On" values were assigned on the basis of field inspections, engineering judgement and comparison with previous studies. Channel On" values typically range from 0.02 for improved concrete channels to 0.10 for overgrown meandering natural channels. Typically, On" values for flood plain areas are higher than channel On" values. Flood plain On" values are often in excess of 0.10. Such high On" values are caused by obstructions such as buildings and dense stands of trees and brush. Table 11-4 summarizes the range of On" values for channel and overbanks used in this study. TABLE ll-4 ROUGHNESS COEFFICIENT SUMMARY Overbanks Channel Minimum Maximum Minimum Maximum Grapevine Creek .045 .09 .04 .055 Stream G 1 .04 .10 .05 .09 Stream G2 .035 .08 .035 .09 Stream G2A .08 .08 .07 .07 Stream G3 .035 .055 .035 .05 Stream G4 .035 .07 .02 .06 Stream G4A .035 .035 .035 .045 Stream G5 .035 .085 .035 .08 Stream G6 .05 .12 .045 .12 Elm Fork .05 .1 .05 .075 Denton Creek .035 .055 .035 .045 Stream D 1 .04 .06 .03 .05 Cottonwood Branch .055 .075 .045 .05 Stream C1 .05 .12 .05 .12 Stream C2 .065 .09 .07 .075 Table does not reflect On" values at bridges and culverts. 11-7 8-11 (n) 'lUnq 8lI!:lq}0 ooueq:> :lIQBl!nOO :lUIeS :lql :lAeq ffiA\ sp:}rOld J:lqlO 'JY.}ll!1W:ld S! l:>:}rOld :lUO p. leql S! :lJ:lq uondwnsse :}1lL 'Sl:>:}roJd uoneweI:>:}J }O ~J1S1L\\Op pue '01 luooerpe '}O ~Jlsdn 'pedW! :lAneInwn:> :lql SM:l~J MOU SWo;) :lql ':lJOWJ:lqpnd 'pooIJ ~A-001 :lql JOj :l8eJ01S 1q uO!l:)nJY.}J lUOOJ:ld SI jO wnwprnw e spu:)wwO:>:}J Sl~1I!8Ug jO SWo;) :)ql 'S:lUW :)Jenbs 01 ueql SS:lI SB:}Je :l8elI!elp ql!A\, S:lpelnqpl JOtqW JOd 'J:)AnI Al!1I!l.L :)ql }O I:)uueq:> 1I!Bw pue }JJOd 1S:lA\ '}JJOd WIg :lql JOj Alpede:> :l8eJ01S A:lIIeA lI! uO!l:)nJY.}J (lUOOJ:)d 0) OU SPU:)WWO:>:}J Sl~1I!8Ug jO swo;) :)ql 'UO!~O jO pJo:>:}~ 8861 WdV l!:)qlUI r- 'lUOOJ:)d LZ J:)qlo :)ql JOj JY.}lunoo:>e UOn:)Id:)p :)8eJ01S A:)IIeA pue ':)SB:}J:>lI! :)ql}O lUOOJ:)d 9 JOj lunoo:>e 01 puno} seM UO!lezJ1rnqJO 'SWo;):)ql Aq JY.}dOI:)A:)P I:)pow :>y80IOlpAq :)ql 8lI!sn 'SlOpej :)S:lql jO ~lJ:) :lql qsnqBlS:l 01 :)pew seA\ 1S:l1 V 'UOn:)Id:)p :)8eJ01S A:lIIeA pue UO!ltrZ!Ueqro :Slopej 0A\l 01 :)np S! suompuoo 8lI!lSJX:) J:)AO :)SB:}J:>U! lUOOJ:)d €€:)1l.L 'S:l8Jeq:>S!p pOOIJ JWA-001 :lql JO} SUon!pUoo 8unspG} J:)AO JY.}~dx:l :lq PInoM lUOOJOO €€}O :lSB:}J:>lI! 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'pue 81I!W!1 ~d pOOIJ sp:}lJe 8~eI JO uoneIsueu 'uo!l:)e l!OAJ~l pue (8~eI) uoneIsuell ~eu:)wou~qd 0A\l 01 ~rqns S! lU:)W:)AOWPOOIJ S!1l.L 'WWllS1L\\Op S:lAOW :)AeM pooIJ e se :)wnIOA lJounJ jO Uo!uod :)WOS :)J01S 01 Alpede:> !Broleu S,WWlls e :)q!l:>S:lp 01 p:lsn WJ:)l :)ql S! :)8eJ01S A:)IIBA :l8el01S A:)IIeA 'q ,-- Halff Associates also evaluated the effects of valley storage depletion as a part of the White Rock Creek Flood Plain Management Study. Several proposed projects on White Rock Creek and its tributaries were evaluated. Five flood plain reclamation projects on the main stem of White Rock Creek were analyzed; two in PIano and three in Dallas. In addition, five proposed channelization projects on tributaries in PIano were evaluated. Valley storages in the reaches affected by the proposed projects were examined with and without the projects. All of the proposed projects were found to reduce valley storage for the loo-year flood. Several of the projects were evaluated for effects on loo-year peak discharges due to this valley storage reduction. For example, a proposed reclamation project on White Rock Creek in PIano was found to have increased downstream loo-year peak discharges by 2 percent due to a 15 percent reduction in valley storage. Likewise, a proposed channel project on Stream 5B27 in PIano increased downstream loo-year peak discharges by 5.6 percent due to a 25 percent reduction in valley storage. These projects were somewhat typical of those examined. While the increases in peak discharges were relatively minor due to these individual projects, the cumulative effect of similar projects on White Rock Creek would be serious. Another test was performed on White Rock Creek in PIano to determine the effect of floodway development on peak discharges. The City of PIano is a member of the National Flood Insurance Program. One major element of this program is the establishment of floodways within a stream's flood plain. The floodways are determined by hydraulic analysis only, and no consideration is given to loss of valley storage. Filling the flood plain as allowed under the floodway concept can increase the flood peak discharge due to valley storage reduction. This increase is not accounted for under current FEMA guidelines for flood insurance studies. White Rock Creek in PIano was evaluated assuming encroachment by fill in the flood plain up to the current floodway delineation. The resulting decrease in valley storage averaged 25 percent on the main stem of White Rock Creek. The increase in loo-year peak discharges due to the encroachment alone was 17 percent at Parker Road in PIano. A similar analysis was performed for Stream 5B27. Valley storage reduction on this stream was estimated at 10 percent. A corresponding 10 percent increase in loo-year peak discharges was determined due to the valley storage reduction only. This demonstrates that upstream changes such as floodway encroachment can translate into downstream increases in peak discharges. An analysis of these results indicates that the effects of valley storage depletion are cumulative and can be responsible for more increases in downstream flooding than any other urbanization change. C. Flood Plain Information This study provides flood plain delineations for the Elm Fork of the Trinity River and tributaries in Coppell. The design flood. in Coppell is defined by ordinance to be the loo-year flood based on fully- developed land uses throughout the watershed. The design flood plain delineations for streams included in this study are shown in Appendix F. For streams with proposed storm water management plans, a revised flood plain delineation based on the recommended plan is also shown in red. Flood plain information for the Elm Fork is from the Regional Environmental Impact Study published by the Corps of Engineers in 1987.(16) Flood plain information for Denton Creek, Cottonwood Branch, and Grapevine Creek are supplied by the City from a drainage study prepared by Kimley-Hom and Associates, Inc. (17) Halff Associates has made a cursory review of this information, but is not responsible for the accuracy and reliability of the information supplied by other consultants. 1. Water-Surface Profile Computation The principal tools of analysis used to delineate the flood plains are two mathematical models, a stream hydraulics model and a flood routing model. The stream hydraulics model is used to establish the 11-9 01-11 09-11 ~Iqe.L U! UA\oqs S! SUompuoo ~sn pueI ~dOI~A~P AIItlJ JOJ ~leln;)Ie:> ~soql pue sg~beqJs!p SId ~ql JO uospedmoo V 08L61 U! 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'Z-:::>3H ~IIe:J 'Sl~~U3 JO SWO;) hWJV OS"n ~lp hq pOOOI~A~P me~Old V o~I~pom oSJe ~le 'smep pue sggppq se qJns 'SJOllUOO JrrnelphH omwlls ~Ql guole SUO!l:Y.)S SSOlJ snopeA 10j uoneA~I~ ooepns l~leM pue ~gleqJS!P U~Ml~q dNSUO!leI~l b. Other Studies ~ Profiles for the lOO-year flood have previously been published in the City of Coppell Flood Insurance Study.(12) In general, the lOO-year flood discharges used in this study, based on a fully developed watershed, are higher than those developed for the Flood Insurance Studies, which used existing (1978) land use conditions. r- TABLE II-S SUMMARY OF DISCHARGES (CFS) MINOR TRIBUTARIES FULLY DEVELOPED LANDUSE STREAM LOCATION DRAINAGE 2- YEAR l00-YEAR AREA DISCHARGE DISCHARGE (Sq. Mi.) USED IN HEC-2 USED IN HEC-2 MODEL MODEL Stream Gl Upstream of Bethel Road 0.64 1000 2900 Stream Gl Downstream of Bethel Road 0.72 1100 3300 Stream Gl Upstream of Coppell Road 0.80 1200 3500 Stream Gl Downstream of Coppell Road 1.11 1700 4850 Stream Gl At the Confluence with Grapevine Creek 1.32 1900 5150 Stream G2 Upstream of Bethel School Road 0.21 365 930 Stream G2 Downstream of Confluence with Stream GZA 0.29 500 1300 Stream G2 At Confluence with Grapevine Creek 0.37 650 1650 Stream GZA At Confluence with Stream G2 0.08 150 350 Stream G3 At Confluence with Grapevine Creek 0.08 160 350 Stream G4 At Woodhurst Drive 0.11 230 720 Stream G4 Upstream of Confluence with Stream G4A 0.18 230 830 Stream G4 At Confluence with Grapevine Creek 0.27 270 1000 Stream G4A At Confluence with Stream G4 0.04 90 230 Stream G5 At Confluence with Grapevine Creek 0.05 55 240 Stream G6 Approximately 300 feet Downstream of Moore Rd. 0.1 250 600 Stream G6 Approximately 1300 feet Downstream of Moore Rd. 0.16 375 850 Stream G6 At Confluence with Grapevine Creek 0.28 600 1350 Stream Cl At Confluence with Cottonwood Branch 0.17 400 1000 Stream C2 At Confluence with Cottonwood Branch 0.08 225 550 Stream Dl Approximately 700 feet Upstream of State Road 0.31 500 1300 Stream Dl Approximately 500 feet Downstream of Coppell Rd. 0.44 330 1500 Stream Dl At Confluence with Denton Creek 0.51 370 1600 11-11 '(;1-11 ":lUJ: 's;ngpossv pUll WOH-kl[lll!)l.\q p;xIO[::J~p ^rmtS a311UflJJ(JD1S"O}f "3dc/o;:) ::Jql mOlJ are ::J[q11l S!Q1 uo S::Jg.req:>sJG p::lqSl::JIRM p;xIO[::J~G Ann.'! z ::ISO pUlrl SUI t OOO'SS oot'LE OO"VOI ::JgRD uoiuo.LlllJ OOS'6t> --- t>6"SU ".18 uOllnH MO[::J8 008'6t> ---- L r'lEI :l[::J::JJ:J ::JU~RJD MO[::J8 ](.1011 mrn 096'9 OOZ9 t>n pool! 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PLANNING INVENTORY A Introduction The City of Coppell Storm Water Management planning inventory includes descriptions of the natural and man-made attributes of the watershed, as well as a detailed representation of environmental features along the creek corridor. The inventory is a compilation of data from diverse sources that can be used in planning and evaluating alternatives for watershed and flood plain management. The specific contents of the inventory include physical and biological components, land use, flooding and erosion sites, and water quality issues and regulations. B. Physical Environment The City of Coppell contains approximately 15 square miles of land which is drained by the Elm Fork of the Trinity River and its major tributaries; Grapevine Creek and Denton Creek. Approximately 36 percent, 5.4 square miles, is drained by Grapevine Creek which ultimately enters the Elm Fork at the southeastern corporate boundary of Coppell. Approximately 53 percent, 7.9 square miles, is drained by Denton Creek, including 2.8 square miles drained by Cottonwood Branch, a major tributary of Denton Creek. The remaining 1.7 square miles drain directly into the Elm Fork of the Trinity River along the eastern city limits of Coppell. The majority of the city is located in the northwest corner of Dallas County, extending into Denton County along the CoppellJLewisville northern boundary. Dallas and Denton Counties are located in north central Texas approximately between the north latitudes of 32"30' and 33"30' and meridians 96"30' and 97"30' west longitude. Gradual changes in elevation are typical of this part of Texas. Ground elevation ranges from about 350 to 900 feet above mean sea level in the two county area. In the City of Coppell, elevation varies from approximately 550 feet above mean sea level in the southwest corner to 420 feet above mean sea level at the confluence of Grapevine Creek and the Elm Fork. 1. Climate The climate of any specific region is defined as the average state of the earth's atmosphere over a long period of time, usually several decades. Short term or day-to-day variation in the atmospheric condition is referred to as weather. The City of Coppell lies at the northern edge of a humid, subtropical climatic zone. The climate is generally mild, with moderate winters and hot summers. Mean annual temperature is 65.50F, with an average temperature of 850F in July and 460F in January. The area has an average of 94 days with temperatures above gooF and 37 days with temperatures below 320F. Mean annual rainfall is 34.5 inches with the heaviest precipitation usually occurring in April, May, and June. Mean annual snowfall is 2.1 inches. Average relative humidity is 64 percent. Prevailing surface winds are southerly. Average wind velocity is 10.9 miles per hour. (1) Natural variations in landform and topography alter the climatic environment characteristic of localized areas, often dampening the effect of regional climatic extremes. When areas in close proximity to each other experience measurable climatic differences, the localized conditions constitute microclimates. North Central Texas creeks and their major tributaries create natural microclimates that differ somewhat from the region's overall climate. These areas typically experience lower temperatures, wind speeds, and solar radiation intensities, and a higher relative humidity. Man-made structures add another dimension to the environment that affects the climatic condition of a localized area. 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J~IOOO 0S{~ S! 11 'J~UIUInS ~V U! AtJP!Ulnq J~qg!1{ pUll ~Jn1~J~dUI~1 J~h.\OI ~^llq 01 spU~l ~l~1lI!I:>OJ:>!UI 1SJ!J ~U (l)'~U!pnnq IIlll hI~^HllI~J hq IY.)punoJJns spJdunoo pu~ Sl~llS h.\OJJ~U (€) pu~ ~SloI 3U!}{Jlld pu~ '~J~nbs 'Sl~J1S S~I~J1 ~P!A\ (Z) ~~}{~I 'SJ~^P 'S}{~J:> }O AtJUPJA ~q1 U! pUllI oo~ds u~do pu~ '~J1 q1!A\ Sl~J1S 'S}{J~d !ffi The Soil Conservation Service classifies soils by their profile or sequence of natural layers. Soils that have profiles which are almost identical make up a soil series. The soil series are then further classified into phases on the basis of differences in slope, stoniness, salinity, wetness, degree of erosion, and other characteristics that affect their use. Areas of two or more soil series which cannot be shown separately on the soil map are classified into phases called soil complexes. Soils within a watershed are often grouped into three broad locational categories of bottomland, transitional and upland soils. Bottomland soils are found within "the normal flood plain of a stream, subject to flooding".(1) Bottomland soils in the City of Coppell are comprised mainly of the Frio, Gowan, Houston Black, and Trinity soil series with small areas of Altoga, Silawa and Ferris-Heiden soils along the flood plain fringe. These are relatively deep sedimentary soils, laid down by repeated flood events over long periods. The Frio and Gowan soils series are made up of friable, loamy, soils with slopes of less than one percent. The Houston Black and Trinity soil series are comprised of deep, calcareous, clayey soils, with slopes that are nearly level to moderate. The Houston Black soils also occur on uplands throughout the watershed and on old alluvial terraces along major streams. The Trinity soils are found mainly in the bottomland areas and are formed in recent alluvium on flood plains.(8) The Altoga and Ferris-Heiden soils are deep, well-drained clayey soils which are sloping to strongly sloping. The Silawa soils are fine, sandy loam soils with slopes greater than two percent. Upland is defined as "land at a higher elevation, in general, than the alluvial plain or stream terrace; land above the lowlands along streams".(9) The transitional soils can be found between the bottomland and the upland soils on stream terraces. These soils often have greater inclines than the upland soils and tend to be eroded and gullied. The transitional and upland soils found within the City of Coppell are comprised of twenty-one soil series, common to both areas. These are the Altoga, Axtell, Bastsil, Burleson, Crockett, Dutek, Ferris, Frio, Gowen, Heiden, Houston Black, Lewisville, Mabank, Normangee, Seagoville, Silawa, Silstid, Smithville, Sunev, Trinity and Wilson soils. The Altoga and Lewisville series consists of deep, well drained silty clay soils which are gently to strongly sloping. The LeWisville soils are found on old stream terraces and the Altoga soils are found on the escarpments of these terraces. The Burleson and Seagoville are nearly level to gently sloping, moderately well-drained clay soils. The Seagoville soils are found on flood plains and the Burleson on old stream terraces. The Ferris and Heiden series are deep, well-drained soils formed in clayey marine sediment. The Normangee, Sunev and Wilson series are all deep clay loam found on uplands, with moderate erosion potential. The Normangee and Sunev soils are moderately well-drained to well-drained respectively. The Wilson soils are poorly drained. The Axtell, Bastsil, Crockett, Dutek, Mabank, Silawa and Silstid soil series are all made up of deep, fine sandy loam. The Axtell, Bastsil and Dutek soils are found on old stream terraces. They are well- drained to moderately well-drained, gently sloping with a moderate erosion potential. The Crockett, Silawa and Silstid soils are found on uplands with the Mabank soils found in depressions on these uplands. Except for the Mabank soils they are all well drained, gently sloping to sloping. The Mabank soils are poorly drained and nearly level. The Mabank and Silawa soils are highly erosive. The Smithville loam is a deep, well drained, nearly level to gently sloping soil found on high bottoms and low terraces.(lO) The Trinity, Frio, Gowan and Houston Black series were also found in the bottomlands of the City of Coppell. The special map unit, Arents, is also found in some areas of Coppell. This map unit is made up of areas that have been mined for gravel and sand. They are usually lower than the surrounding landscape, gently undulating and do not contain uniform soil layers. The soil series and their phases found within the City of Coppellare listed in Table III-l. Figure III-I is a General Soil Map of the city showing the major soil series grouped by location. 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L&.ZZO we( CJ..I> e(~ 00 ~ e (/) i: 'OA1S HnHIHV <9 z '> g; a: ~ z ~$ ~ ~ :;:: u.. C ~ i; --, C. Biological Environment - Vegetation and Wildlife Land use or land cover directly influences the type and diversity of both plants and animals inhabiting an area. It is generally held that the greater the diversity of species, the more desirable the habitat type. Therefore, when a habitat supporting a highly diversified population of biota is replaced by a habitat supporting a less highly diversified population of biota, environmental degradation occurs. The converse is also true, a low diversity supporting habitat converted to a higher diversity supporting habitat creates environmental enhancement. (11) The habitats with the greatest diversities include: grasslands, fence rows, woodlands, wetlands, and water bodies. Urbanization of the flood plain, which disturbs the grasslands, woodlands, and waterways, is an example of environmental degradation. Conversely, the reclamation of former agricultural areas or cleared forest lands by native grasslands and regenerated forests is an example of environmental enhancement. I The presence of wildlife is intrinsically dependent on the quality and quantity of these suitable habitats. Within the generally recognized habitats of the Blackland Prairie, the water bodies, woodlands, grasslands, fence rows, and wetlands contain the greatest number of animal species. The flood plains within the City of Coppell provide a diverse ecosystem containing all these suitable habitats. The preservation of these diverse habitats adjacent to one another is considered an important aspect of wildlife management. (ll) During the course of this City-Wide Storm Water Management Study, employees of Halff Associates made numerous site visits to review flooding complaints throughout the city and inventory the stream corridors. Tree species, major tree stands, unique vegetation and significant environmental features were identified. The characteristic vegetation and wildlife species located and sited within the City of Coppell are discussed in the following sections. 1. Vegetation The City of Coppelllies in the Blackland Prairie vegetative zone of the Texas biotic province. A biotic province is defined as a continuous regional geographic area characterized by the occurrence of one or more ecological associations that differ significantly from the ecological associations of adjacent provinces. (13) In general, the Texas biotic province is characterized by peculiarities of vegetation type, ecological climax, climate, geology and soils, which distinguish it from the moist forest of East Texas and the dry grasslands of West Texas. The Blackland Prairie vegetative zone within this province is characterized by gently rolling to nearly level topography, with dark-colored calcareous clay soils that support prairie grass-forb vegetation. The vegetative zone is further divided into three community classes distinguished by physiographic features: (1) the deep soil prairie, (2) the thin soil prairie, and (3) the. clay or limestone ravine.(14) Within these categories, a complex combination of habitats exist: the upland and transitional region grasslands, the mature forest lands, the flood plain wetlands, and the water bodies. The deep soil prairie is composed of heavy calcareous clay, which originally supported tall and mid-height grasses. This area comprises the majority of the upland soil grasslands, which historically was prime farm land and is becoming urbanized. The thin soil prairie is underlain by the Eagle Ford Shale. The dominant vegetation of the thin soil prairie includes the mid-height and short grasses and a variety of dry site herbs. This category comprises the transitional soil grasslands. The ravine or flood plain category provides the best environment for trees in the Blackland Prairie zone. The shade, the concentration of runoff water, and a proximity to ground water are the major factors contributing to the growth of small hardwood forests in these areas. The upland and transitional grasslands of the study area could contain as many as 135 species of plants, which is the largest number of individual plant species of the study area habitat categories. These II1-6 L -III jO At!:) ;}ql tl!Ql!^\ spU~ll;}A\ "S"e;}l~ PU~Il;}M. ;}P~W-~W lO I~lnl~U ~nOlQl lU;}nUJ;} ;}ql .l;}lIY. 01 51 AtH~nb l;}l~M. Wl01S jO lU;}W;}JU~qu;} lOj ,.{gOIODq::>;}l guPil;}W;} ;}UO .AtH~nb l;}l~M. S,WWllS ~ UO ;}JU;}nlJU! lUmlOdlU! U~ O~ ;}l~ SP~ll;}A\ "POOj lOj SlUm!q~lJU! spu~ll;}M. ;}ql UO pu;}d;}p q:>!QM. 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Wildlife A rich variety of wildlife exists within the City of Coppell despite the rapid urbanization of the area. Habitat destruction through removal, physical alteration, and/or pollution is the primary challenge facing the region. Mammals such as black bear, red and gray wolves, mountain lion, river otter, and bison have disappeared due to habitat destruction, hunting, trapping and behavioral intolerance of human activity. (11) However, species such as raccoon, opossum, striped and spotted skunks, gray and red foxes, coyote, bobcat, cottontail and swamp rabbits, fox and flying squirrels, beaver, armadillo, bats and numerous small rodents persist despite human encroachment. All of these mammals reside predominantly in the woodlands with the greatest density and diversity in the minimally disturbed areas. Table III-2 is a list of the mammal species usually found within the study area. Those recently sited in or near Coppell are marked with as asterisk (*). The more intolerant species of birds, amphibians, and reptiles have also suffered greatly from the encroachment of civilization. However, tolerant species such as the house sparrow and the red eared slider (turtle) have flourished. CIS) Bird diversity is very high in both the grasslands and woodlands, with 57 species known to inhabit the grasslands and 60 species in the woodlands. As would be expected the majority of the forest land species are perching birds. Most grassland species are seed eaters or feed on insects. Red- winged black birds, belted king fishers, blue jays and numerous sparrows were spotted during the field reconnaissance of the streams in Coppell. Two species, the peregrine falcon and the whooping crane are on the Federal rare and endangered species list and could stop over in this area during fall migration on their way to the Texas coast. Unlike birds, reptiles and amphibians are more common to the woodlands than the grasslands, primarily because of the close proximity to water. One turtle species (the Western box turtle), the infamous Texas homed lizard, and two poisonous snake species are relatively common to the forest lands of Coppell. The qualitY of the fishery habitat has, in general, decreased throughout the Trinity River watershed in the Dallas-Fort Worth area, due to development-induced erosion causing stream turbidity and pollution causing low dissolved oxygen concentrations.(19) However, the water quality along the Elm Fork and its tributaries in Coppell is still relatively good. The two most abundant species in this area are the red shiners and bullhead minnows. Table III-3 list fish species expected to occur in this area. Those recently sited are marked with an asterisk (*). Some of these were even sited within the developed reaches of the creeks, such as blue gill and largemouth black bass along Grapevine Creek near Denton Tap Road. III -8 6-III .(S1!r.)~ 'qUOA\ uo.~) !;;}!JD11Icy.JJ. pu1J Dttm ~J. '1u;nu;m7tS l:Wdtu] lTJ1WWUo.lJttuy [DU~N ifTJ.I(f 'P!J1S!G quoA\ Uo.'! 'Sl;);)~U3 JO sdIO:J ,{ULIV'S'fl ::mnos n;xldO:J II! {Y.)A.!;)S(j 0 - . 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S3I::Y.!IdS 'lVWWVW ~.m :>rIUV.L r- TABLE ID-3 FISH SPECIES WITHIN THE STUDY AREA COPPELL, TEXAS Common Name Scientific Name * Threadfin shad Dorosoma petenense * Carp Cvprinus carpio Golden shiner Notemigonus crvsoleucas * Red shiner Notropis lutrensis * Bullhead minnow Pimephales vigilax * Fathead minnow Pimephales promelas * Blackstripe top minnow Zvgonectes notatus Stoneroller Campostoma anomalum Flathead catfish Pvlodictus olivaris * Yellow bullhead catfish Ictaluris nactalis Tadpole mad tom Noturus evrinus * Mosquitofish Gambusia affinis * Largemouth bass Micropterus salmoides * Green sunfish Lepomis cvanellus Longear sunfish Lepomis megalotis * Dollar Sunfish Lepomis narginatus * Bluegill Lepomis macrochirus Dusky darter Percina sciera Bluntnose darter Etheostoma chlorosomum * - Observed in Coppell D. Land Use and Demographic Change Early settlers in the area which is now Coppell, Texas found rolling, tall grass prairies laced with wooded streams of clear water and abundant wildlife. This fertile countryside with plentiful rainfall and a nine-month growing season seemed destined to become agricultural land. With the advent of the railroad passing through Coppell (then Gibbs) in 1889 the town became a thriving farm community.(20) In the 1950's, a change began taking place as the cities of Carrollton, Irving, Grapevine and especially Dallas began annexing land near Coppell. To prevent this, the citizens of Coppell banded together to incorporate the town in 1955.(21) As the Dallas-Fort Worth metroplex area grew, land values increased and the farming community became a thing of the past. Coppell established its city charter in 1%5 with a population of slightly less than 700 people. The opening of the Dallas-Fort Worth Regional Airport in 1972, immediately to the southwest, followed by the construction of IH635 in 1980 led to the city becoming one of the fastest developing areas in the metroplex. (22) 1. Historic Land Use and Archaeological Sites There are seventeen archaeological sites in or bordering the City of Coppelllisted with the Texas Archaeological Research Laboratory in Austin, Texas.(23) These sites have been recorded by both professional and amateur archaeologists since 1940 but an intensive investigation has never been conducted. 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Campsite evidence; mussel shells, two arrowheads, one dart point, limestone hand axe or chopper, flint fragments. 41-DL-27 Burial site, human skeleton found 1939, site recorded 1941. 41-DL-30 Campsite, recorded 8n1. Campsite evidence; projectile points, scrapers, choppers, knives, a double bit axe, and two netsinkers. One human skull also discovered. 41-DL-31 Type of site unknown. Site may have been destroyed by gravel operation. 41-DL-299 Campsite, recorded 8189. 41-DL-300 Campsite, recorded 9189. 41-DL-252 Campsite, recorded 4185, disturbed by erosion. 41-DL-2% Campsite, recorded 11188, disturbed by erosion. 41-DL-297 Campsite, recorded 11188, disturbed by erosion. 41-DL-11 Campsite, recorded 12/40. Site had been pothunted. 41-DL-301 Lithic scatter, recorded 12189, disturbed by erosion and future construction. 41-DL-309 Location provided by Texas Archeological Research Laboratory. No description available. 41-DL-193 Location provided by Texas Archeological Research Laboratory. No description available. 41-DL-13 Location provided by Texas Archeological Research Laboratory. No description available. 41-DL-281 Location provided by Texas Archeological Research Laboratory. No description available. 41-DL-295 Location provided by Texas Archeological Research Laboratory. No description available. HISTORICAL PARKS: Grapevine Springs Park Natural springs site where Sam Houston camped in 1843. Federal Works Progress Administration developed park in 1936 by constructing retaining walls, bridal paths, a baseball field, three bridges, and a historical marker where Houston had supposedly camped. Park was later abandoned. Only partial remains of one bridge, part of the well, and the unmaintained retaining walls now remain. BURIAL SITES: Historic Bethel Cemetery State historic marker dedicated on September 10, 1989. First burial in 1859. All but two of the initial 200 graves have been lost to vandalism and development. Sources: Correspondence with Rosario Casarez of Texas Archaeological Research Laboratory at the University of Texas at Austin, July, 12, 1990. Lou Duggan and Jean Murph, eds., The Citizens Advocate Journal of Coppell Hiswry, Book 1, Centennial Edition, 1890-1990, (Coppell, Texas: Citizens Advocate, Apri1199O). III-12 n-m 'Slu~m~^OldUl! ~lnl:lOllS1UJU! PU-e ~P!^p:l-e redp!Unm AU-em uoddns Ol JY.}~U ~s-eqxtn ~tp ~P!^old ffi^\ Slu~mdoI~^~P I-epl~mmoo pu-e I-ePlsnpU! ~~1l.L 'S€9HI 8uore JY.}l-eu8!~p ~sn I-epl~mmoo pu-e ooYJo ql!^\ I-eptsnPU! lq8n lOJ AJ!l"empd JY.}l-eIS S! ~l!S S!1l.L 1>-e0'M UOlto;) l-e A-eMJ{l"ed UOdOOld JO l~M '){l-ed s~U!sna A-eM~l-eD '~l!S ~l:l-e SZZ -e 8U!doI~^~P AnU~llro OSJ-e S! 'l~dOI~^~P lOf-em l~tpOu-e '(At~'M ~d mu-es AJl~WlOJ) UOp-elOWo;) lu~mdoI~^~a snn~l1D (K)'~xoq JY.}l-e8nnoo JO uopnqplS!P pu-e ~8-elOlS lOJ ~Oq~l-eM -e pnnq Oll:l-ellUOO l~pUn ~l:l-e ~^!J s-eq AP~lJ-e 'UOlnO.I.l1Q U! 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For example, along Grapevine Creek south of Southwestern Boulevard the natural scenic creekside vegetation has been disturbed by channelization. However, there are still some scenic wooded areas along Grapevine Creek where developments have preserved the natural channel. Wooded areas also exist along Cottonwood Branch in western Coppell. These scenic reaches extend east past Thweatt Road to Denton Creek passing through several private residential subdivisions where the natural flood plains have been preserved. The Denton Creek flood plain east of SH 121 down to its confluence with Cottonwood Branch also has a high scenic value. These wooded areas provide habitat for a variety of wildlife. Mature species of bur oak, cedar elm and cottonwood are observed adjacent to the channels. Through the central and eastern portions of Coppell, much of the land adjacent to the flood plains of Grapevine Creek, Denton Creek and the Elm Fork of the Trinity River is developed or under construction. Adjoining development has destroyed many of the natural features but strips of natural wooded areas remain through several of the private residential areas. Creekview Addition and part of the Northlake Woodlands Addition borders one of these scenic reaches along Grapevine Creek. Blue gill, large mouth bass and a variety of birds including red-winged black birds and belted king fishers were spotted during the field reconnaissance of this reach of Grapevine Creek. The flood plain has also been left in its natural state through residential neighborhoods along several of the tributaries of Grapevine Creek. Mature Pecan and other varieties of trees can be seen in these areas. There are also some environmentally sensitive reaches of the Elm Fork and Denton Creek that have been retained as natural. The Riverchase Golf Course borders the Elm Fork upstream of Beltline Road. The golf course contains rolling hills maintained as manicured lawn with mature hardwoods immediately adjacent to the river. Several reclamation projects exist along Denton Creek but for the most part the actual chaimel and immediately adjacent flood plain have not been disturbed. These natural creek corridors with unique vegetation and wildlife provide refuge in the urban landscape and add to the quality and scenic value of the City of Coppell. Preservation of these areas will provide the current citizens of Coppell with prime locations for passive recreation as well as helping to attract future residents to the city. 2. Open Space Planning Open space in this study is defined as undeveloped land available for a number of purposes ranging from providing recreational opportunity to preserving unique vegetation and wildlife habitat. The concept of open space has changed significantly since the 1800's when the entire area was mostly open, and settlers were compelled to develop or occupy the space. For example, in 1880 Dallas County had an estimated population of only 33,488 people.(38) The population rapidly increased to 1,556,385 people in 1980.(39) As the population increased, more and more of the open space was converted to urban land, providing residences and places of employment and trade. As urban development continues, citizens have become concerned about the ultimate form and character of their environment. If a natural open space structure is to exist under a fully developed condition, the land must be identified, planned, and preserved in advance of development. Concern over the significant depletion of natural open space and decreases in rural land use prompted Dallas County to develop an open space plan that describes the existing environmental condition of the county and recommends county- wide open space programs. Objectives of the program include: . provide sufficient open space to meet the recreational and scenic landscape needs of the citizens, . protect a diversity of landscape and habitat types, . determine critical areas considering flood plain corridors and water features as important elements, and III-16 Ll-III At!U!l.L l~ddn ~lll uo uod~'M OOU'BSSreuuo:Y.}'M Sl~~U3 }O sdJOJ ~llL "{'BJnl'BU lI!'Bm~l }flOd UI[3 ~ql PU'B }f~lJ UOlU~a }O S}fU'Bq ~ql1~^~MOq '~SlnOJ 110D ~S'BqJ1~^rn 10} oo'Bds u~do ~l'B^!ld S'B lY.)doI~^~P u~q S'Bq lI!'BId pooIJ }f10d UI[3 ~ql }O At!lof'Bm ~gmI V "sn'B1l ~JP.q pU'B ~JP.q 10} lS!X~ filS ~munuoddo lnq AI~l'B^!ld pOOOI~^~P u~q Ap~l{'B S'Bq lI!'BId pooIJ !;!lIl }O q:mw "l~^rn At!U!l.L ~ql }O }f10d UI[3 ~ql Ol uO!l~uuoo lI~qU~~ ou SJ ~l~ql 'S}f~l:> Sl! }O AU'Bm UO ~l!S }f1'Bd S'Bq n~ddOJ }O AtD ~ql qgnoqlIV "Ol-IA ~1~!d 'IA l~ld'BqJ lI! 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'I'BdpIUnm 1ll!M Atunoo ~lll }O SUOJj~ ~l'BlI!PlOOO . River Basin released in March 1990 states that multi-use trails and public open space land close to homes is the highest priority recreational need to the Dallas-Fort Worth metroplex area. They state a regional goal of linking Lewisville Lake, Lewisville, Coppell and Irving with a trail system located along the Elm Fork.(4S) Even though much of this land is already developed, the possible acquisition. of trail easements should be pursued in partnership with Corps of Engineers efforts. TABLE ill-6 EXISTING AND PROPOSED PARKS IN COPPELL STATUS PARK. NAME APPROXIMATE AREA (in Acres) Existing Andrew Brown Community Park 51.3 Existing Coppell Community Park 114 Existing Hunterwood Park 4.0 Existing Bethel Road Park (Leased) 4.0 Existing The Duck Pond 9.3 Existing Villawood - Greenbelt Park 3.3 Existing Grapevine Creek Park 30 Existing Allen Road Pocket Park 5.5 Existing Parkwood Park 0.5 Existing North Lake Park - (Dallas) N.A Proposed Magnolia Park 30 Proposed Lake Park 33.2 Proposed Grapevine Springs Park 23 Proposed Riverchase Linear Park 55 Source: Existing and Proposed Park Sites obtained from City of Coppell Parks and Recreation Department files, June, 1990. 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UMOqS lOU ~J-e Slu~m~sw pu-e A-eM-JO-Slq~J'M o~l~Idmoo sA-eMI-e lOU SJ UMOqS dJqSJ~UMO 'm-ep lU~JJro ~lI!lI!mqo lI! Atln:>!mp ~ql Ol ~na oSUOJSJAJpqns JY.)dOI~^~P AIM~U JO Sl-eld pu-e su-eld ~ql pu-e sd-em AlJ~dOJd Atp mOlJ JY.)ndmoo s-eM m-ep dJqSJ~UMO 'n~ddOJ 1Il 0.1 Jqpu~ddV '~l-eld UOJl-epunlI! pOOIJ ~J~P ~ql uo UMoqs SJ n~ddOJ JO At!:) ~ql lI! dJqSJ~UMO AlJ~dOJd dJqSJ~1L\\() AtJ~dOJd of: Sanitary sewer mains exist in the flood plains of Grapevine Creek, Cottonwood Branch and portions of Denton Creek. As development continues through western and northwestern Coppell, new sanitary sewer mains will probably be constructed within the flood plains especially along the upstream reaches of Denton Creek. This construction should be performed in such a manner as to minimize channelization and disturbance of the natural environment. Water and natural gas mains cross the creeks of Coppell in many locations but in general they are not located within the flood plain. These crossings usually coincide with road crossings. There is also a petroleum line belonging to Conoco Pipe Line Company which passes through the city immediately south of the St. Louis and Southwestern Railroad. A portion of this pipeline is in the Elm Fork flood plain. 6. Existing Fill Cases Land developments often encroach on the flood fringe and flood plain to reclaim these areas for residential, commercial, or industrial development. Flood plain activities within the City of Coppell are regulated by the City of Coppell Flood Plain Ordinance. A Flood Plain Development Permit is required before any construction activities begin on land within a flood plain. This permit must be signed by the Flood Plain Administrator (City Engineer) and the permit number along with the administrators signature is required on the plat for the subdivision. Existing and approved fill cases within the City of Coppell are shown on the plates in Appendix F. Table III-7 contains a list of these permitted flood plain fills and the current status of construction. III - 20 lZ-III pOOOI:l.\:lQ 10U UO!11n!1:lUU11tp Plllr1 - :ll:lldwo;) pUll UO!llllIml:>:llJ: :lUlrllllholJ: .re:lU UO!l!PPV ql-ION l-Iod:l:Ud q:)ullJH pooMuollo;) UO!1:llU1SUOO J:lpun - p:lAOJddy :llllJ!.lJ Ulllld POOO lIuol1llTlil UO!l!PPV PU:lH ~1l0 q:lUllJH pooMUOllo;) :ll:lldwo;) :llllJ!.lJ lI!llld POOO lIuol1l illd :l11l1sg SPOON\. MOpeqS q:lUllJH pooMUOllo;) :ll:lldwo;) :llllJ!.lJ lI!llJd POOO lIuol1llTlil :llllr1 MOnoH lIlI!plI!N\. lIuOl1l q:lUllJH POOMUOllo;) }O S:lll1!ffiA q:lUllJH POOMUOllo;) lunH 10U - p:lAOJddy uO!1llwllJ:>:llJ: 'P^lH AIl~J1!d }O qlnoS n:lddo;) }O qJlld q:lUllJH pooMUOllo;) pOOOI:l.\:lQ 10U pUlrl - :ll:lldwo;) UO!lIlWllJ:l:llJ: 'P^lH AIl~J1!d }O ql-ION n:lddo;) }O qJlld q:)ullJH POOMUOllo;) 11!nH ~:l:UJ 10U - p:lAOJddy UO!lllW1!J:>:llJ: }O :lP!sqlnoS pllOlJ: dill. 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U01U:lQ 01 'l!'lJ:'N\.'S 'fl 'TS - 1S1!3 SPUIlIp<>oN\. :l'l1!Jql-IoN ~:l:lJJ :l~llJD UO!l1!WllJ:l:l.1 'P^lH mq1JV:lllW :ll:lldwo;) pUll uO!11n!1:lUU1lqJ 01 ~JOd WJ3 :l:lu:lnouo;) - III uO!1:>:lS PjJ1SJQ IOJ1Uo;) POOH lIu!^JJ ~:l:UJ :l~llJD :ll:lldwo;) S011l1S uO!1d!J:lS:lQ UO!1ll:><Y"V1u:lwdOI:l.\:lQ W1!:lJ1S svx:iLL 'TI3ddO::> STII.iI NIYId GO<YI.i mISOdOlld aNY 9NLLSIX:!I L-m 3'18V~ 7. Solid Waste Disposal Sites Landfills have historically been sited in flood plain areas and are important considerations with respect to non point source pollution. Over time, water will percolate through the buried solid wastes and extract dissolved or suspended materials. These liquids are called leachates and can affect the quality of groundwater and adjacent stream flows. The North Central Texas Council of Governments has estimated that by this year (1990) the volume of solid waste generated by the Dallas-Fort Worth region will be 119,050 tons per week. This is 178 percent of the volume generated in 1975.(47) There are two abandoned land fill sites within the City of Coppell; one on Denton Creek and one near the Denton Creek/Elm Fork confluence. Both of these sites have been reclaimed for development. One currently active solid waste disposal site remains on the Carrollton side of the Elm Fork immediately south of Sandy Lake Road next to McInnish Park. An additional land fill site is proposed in Carrollton between the Elm Fork and Denton Creek with access from Sandy Lake Road in Coppell. This landfill has not been approved. 8. Flooding Sites Flooding which may impact residential, commercial, or industrial development includes the inundation of either structures or accessways, resulting in the disruption of the normal activity for which they were designed. The first floor elevation for buildings and the lowest top of road elevations for stream crossings are key elevations used to determine the severity of flooding. Stream flooding sites inventoried within the City of Coppell are listed in Table III-8 and shown on Figure III-4. Flood Plain Management alternatives to alleviate the flooding were developed on Grapevine Creek, Cottonwood Branch, Denton Creek, the Elm Fork of the Trinity River and nine tributaries of these streams. These alternatives are discussed in Chapter VI. r- In addition to stream flooding sites found during the flood plain management phase of this study, local drainage complaints were also inventoried. A compilation of these complaints, received during the study and found during the review of city files is included in Appendix C. A Natural Drainage Subcommittee made up of volunteer citizens working together with city staff identified many of the drainage improvement needs. This committee toured sites during 1989 and prepared a list of over 40 drainage problems, including many of the complaints registered by local property owners. Table III-9 contains the local drainage problem sites not directly related to the streams listed above as compiled from the subcommittee list and 179 drainage complaints. Alternatives to alleviate this flooding are discussed in Chapter VII. They are also shown on Figure III-4. Table 1-1 in Chapter I lists the sites noted by the subcommittee with references to the Chapter and Section of this report where the problem is addressed. r- In general, the City of Coppell's flood plain management efforts have been successful in keeping houses out of the l00-year flood plain. This report shows only 15 occupied residential structures and one apartment building inundated by the 100 year design flood (fully developed watershed). Ten of these structures are in older areas of town which are expected to redevelop in the future. These are primarily along Stream G 1 near the intersection of Bethel Road and Coppell Road and on Denton Creek along DeForest Road. The other five structures are on Grapevine Creek and Stream G6 near the intersection of Bethel School Road and Hawk Lane. The local drainage complaints relate primarily to undersized storm sewer systems or open ditch drainage systems which are no longer functioning as designed. The majority of these types of problems will be eliminated from future subdivisions because the City of Coppell is now requiring 100 year (fully developed watershed) design criteria for all new drainage construction. r- III-22 a-III ~UON ~uoN ZJ mWllS pRO'M ~lms ~uoN 1:::> mWllS pRO'M ~lms gUJPooH }{lRd 1L\\Olg M~lpUV (pRO'M ~}{'ll'l ApURS) pRO'M n~ddo:::> pRO'M ~lms - 1 q:mRlg POOMUOUO:::> plR^~Inog }{lRd ~lRlOdlo:::> pRO'M n~ddo:::> ~uoN 10 mWllS ~uoN pRO'M l~lOJ~O - € }{~l:::> UOlU~O l~^rn pRO'M ~}{'ll'l ApURS Slu~mllRdv uo~um~A\ At!UJl.L ~ql JO }{lOd WI3 pRO'M ~lOOW ~U'll'l }{MRH 909 'W9 - Z pRO'M Iooq:>S I~ql~g pRO'M Iooq:>S I~ql~g lOL - 1 90 mWllS ~U'll'l !lspq;) ~^!l0 l~llR:J ~UON SO mWllS ~^!l0 smH gUJnO'M ~UON VtO mWllS ~^!l0 lSlnqpOOA\ pRO'M Iooq:>S I~ql~g pRO'M }{~l;)MOpWW gUJPOOH PlRA}{:>Rg to mWllS pRO'M }{~l;)MOpWW gUJPoOH PlRA}{:>Rg €O mWllS ~uoN ~uoN vzo mWllS ~uoN ~uoN ZO mWllS l~llS UOWWRH pRO'M I~ql~g ~UJPTIng ~gRlOlS ':>S!W pRO'M n~ddo:::> ~U'll'l q:>O'l - Z l~llS n~q:>l!W pRO'M I~ql~g - Z ~nu~^V UOSl~PUV pRO'M n~ddo:::> - 1 pRO'M Iooq:>S I~ql~g l~llS n~q:>l!W - 1 10 mWllS pRO'M I~ql~g pRO'M Iooq:>S I~ql~g pROlTIR'M A\S "iJ SJnO'l 'lS pRO'M pRO'M ~UJ' lI~g Iooq:>S I~ql~g SZL 'IZL 'lOL - € }{~l:::> ~UJA~dRlO s.\OMpBOlI paPOOI.!l sa.mpl1.llS paPOO~ JO uoptr.')()'} pu~ # mtr.l.ll S TI3ddO:J .!IO A.LI:J saLIS DNIOOO'lil WVIDI.LS s-m :!fIHV.L TABLE m-9 LOCAL DRAINAGE PROBLEM FLOODING SITES CIlY OF COPPELL SITEILOCATION DESCRIPTION Freeport ParkwaylSouthwestem Blvd. Street flooding Bullock and HoweU Street Yard and garage flooding Brooks LnlHunterwood Subdivision Street, yard and garage flooding Cozby StlHunterwood Subdivision Backyard flooding Kaye Street (north) Backyard flooding Kaye Street (south) Backyard flooding Golden Triangle Mobile Home Park Entrance Road flooding Cottonwood Estates Yard flooding Summer Place Addition Street flooding Sandy Lake Road @ Whispering Hills Drive Yard and driveway flooding Shady Dale Lane Backyard, house and garage flooding 625 Swan Drive Street and front yard flooding Sandy KnoU at Woodhurst Street flooding Sandy Knoll at Shadowcrest Street flooding Meadowridge Condos House flooding Town Lake Apartments Parking lot flooding Samuel Boulevard Street flooding Austin Property Yard flooding Meadows Subdivision Street flooding Mapleleaf Lane Street flooding Magnolia Lane Standing water Raven Lane Standing water Highland Meadows Subdivision Standing water. - entrance road DeForest Road Street flooding LeavaUey Lane Front yard flooding Arborbrook Lane Front yard flooding Rocky Branch Lane Front yard flooding Fieldcrest Loop Front yard flooding III -24 SZ-III . ql!^\ SJY.}qSJ:llnM 811!doI:lA:lQ ooounlnq S!1Il sqJnlSW q:l!1lM Al!^!pn uommoo n S! lY.)qSJ:llnM n JO UOn1rZ!unq1n oSMOrrOJ UO!l1rZ!I!qmS:)l JO pop:ld n pun U:l~Olq S! oounlnq :lql 'I:lUUnq:l 10 lY.)qSJ:llnM :lql l:llIn :lJnlnU 10 unm JO S:)!l!^n:ln :lql n oUl:lllnd MOll :lql JO UOnn1:llln un 10U S! :ll:lql sn 8uOI sn S:)01l!1UOO UO!l!puoo :l{qms S!llL OUO!SOl:l JO :lln1 :lql SInnoo uO!l!sodS!p JO :lln1 :lQl ':lIqms S:)mOO:)q m~lls :lQl U:lQA\ OUO!SOl:l JO ~ln1 ~ql S:)q:ln01ddn uO!l!sod:lp JO :lln1 :lql 'S:)lolnm m~lls :lql SV ouo!l!sod:lp JO :lmoloA :lql unql1:ll~18 1nJ ~q II!^\ q:l~llnIO:l!llnd n mOlJ UO!SOl~ JO ~moloA ~Ql ArrnnfUI oI:lUUnq:l1:l81nI n 811!Wl0J Arrn10lnu '~poj:l Arrnnpn18 II!^\ ~q pun smolloq I~uunq:l:lQJ. 0811!P01~ S! 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UO!S013 lY.)qSJ:llnA\ (n uO!l!sod~Q pun UO!S013 06 expanding impervious areas, reduced infiltration rates, increased runoff, increased flood peaks and increased flood frequencies often suffer severe erosion problems. The higher discharges and velocities increase channel erosion, thus creating a larger channel. Structures near the channel are often imperiled and, in some cases, damaged by the eroding banks. This process is shown graphically in Figure III-3. c. Erosion and Deposition in the City of Coppell All of the above factors are active in the erosive forces prevalent in the City of Coppell. Deep, swift moving channels have been created by decades of natural flows through soils of varying resistance. Continued urbanization increases the magnitude and frequency of erosive flooding. The boundary shear forces exerted by the water on the soil are being modified by recent flood plain fill cases and storm water diversions as urbanization of the adjacent areas expands toward the flood plains. Erosion sites were identified during the walking inventories ofthe streams in Coppell, as well as, from the log of drainage complaints. These sites are listed in Table III-lQ and also included on Figure III-4. The sites listed under Stream Sites are discussed in Chapter VI. Those listed under Local Sites are discussed in Chapter VII. In general, the most severe erosion sites are along Grapevine Creek and its tributaries, which is also the most heavily developed area. Urbanization and flood plain encroachment has increased flows and velocities through these areas causing the loss of trees, fences and storage buildings. So far, no perinanent residential structures are threatened. The few local erosion sites inventoried are on man- made channels or ditches. All of these erosion sites are the results of human activities which have altered the channel, flood plain and watershed. The re-grading and re-direction of channels along with increased impervious areas and underground storm sewer systems throughout the city has altered flow patterns creating unstable stream channels. In most cases, the erosion and any related deposition should be monitored and corrected only as it threatens existing structures or causes increased flooding. The stream channels should be allowed to stabilize naturally, if possible. Corrections for the specific severe erosion problems which may eventually threaten structures are discussed in Chapter VI and VII. Effective erosion control measures for construction sites should be strongly enforced. TABLE 1lI.10 EROSION SITES - COPPELL, TEXAS Stream Location Description Grapevine Creek Downstream of I.H. 635 Severe channel erosion Downstream of Denton Tap Rd. Severe bank erosion; failure of retaining walls Unnamed Trib at Maywood Circle and Meadowcreek Rd. Channel erosion; retaining wall failures Stream G 1 Parallel to Loch Lane Channel erosion Stream G2 Parallel to Plantation Dr. Channel & bank erosion Stream G5 Carter Dr. Erosion upstream through private property Christi Ln. Erosion downstream face of culvert Stream G6 U.S. Bethel School Rd. Channel erosion upstream of culvert D.S. Moore Rd. Channel & bank erosion Stream Cl . State Rd. Erosion upstream of culvert Denton Creek Andrew Brown Park Spillway Erosion at spillway Parkwood Channel Downstream of Parkway Boulevard Channel erosion Woodridge Channel Upstream of MacArthur Boulevard Channel erosion; slope failure III - 26 E-III 3I:1n~l.:I 'PUUVlfJ pCJpnuap '!ilSn uv SUlaval 'lV1.lalvlU pal{gnols al{l aaolUa.l saw1J luanbasqns 'puumfJ alii 01Ull{SnolS sapls pajV.lnlVS daals al{I'saplsqns .lCJ1Vm al{l ual{M 'S.lapUlJCJlU IV lillvpadsa 'pUUVl{J al{l Jo sapls al{l s.mOJS IVl{1 ag.lVl{JSIP llnJ-){uvq v l{Um sUlgaq apro CJl{.L 1< ....-,.".,.>t:...,....... UOl1V.lnSYUOJ ){uvq.lCJao/puuvl{J SUl1S1X1 J F. Water Quality The water quality of streams and rivers can be affected by a number of factors. Natural occurrences such as saline pollution and sediment transport affect stream water quality. More significantly, man's influences in the form of wastewater treatment plant effluents and urban storm water runoff often degrade a stream's water quality. This section will address storm water quality issues for streams in Coppell. 1. Federal, State, and Local Criteria Water Quality Standards and Criteria for surface waters in the State of Texas are described in the Texas Surface Water Quality Standards.(48) The Texas Water Commission assumed responsibility for application and development of these standards in September 1985. Current water quality standards are designed to meet the goals of the Clean Water Act, Public Law 95-217, as amended by the Water Quality Act, Public Law 97-117. They require that water quality support aquatic life and contact recreation uses, where attainable. The Texas Surface Water Quality Standards presents general water quality criteria that are applicable to all surface waters in the state, as well as, establishes numerical criteria applicable to specific surface waters. The Antidegradation Statement, Section II, requires that water quality standards established by general and numerical criteria will be maintained and protected consistent with the provisions of the Texas Water Code. The Texas Water Commission has established numerical criteria for the Elm Fork of the Trinity River and Denton Creek. Other tributaries of the Elm Fork in Coppell do not have established water quality criteria. The Elm Fork is designated as Segment 0822 of the Trinity Basin and is described as "Elm Fork Trinity River Below Lewisville Lake". Denton Creek is designated as Segment 0825. Numerical criteria for both the Elm Fork and Denton Creek are assigned for designated water uses. This criteria includes chemical parameters, dissolved oxygen, Ph, bacteriological factors, and temperature. Water use categories include; recreational, aquatic life, domestic water supply and other. Both the Elm Fork and Denton Creek are maintained as suitable for contact recreation. Criteria for contact recreation require that fecal coliform content shall not exceed 200 colonies per 100 ml as a geometric mean based on a representative sampling of not less than 5 samples collected over not more than 30 days (2001100 ml - 30 day geometric mean). A high (H) quality aquatic habitat designation is given for the Elm Fork and Denton Creek. High quality aquatic habitat classifications require that all dissolved oxygen (DO) concentrations shall be maintained at not less than 5.0 mg/l for freshwater habitat. These streams are designated for public water supply. Chemical parameters include; chloride, sulfate; total dissolved solids, and dissolved oxygen. State criteria requires that annual average concentrations not exceed 80 mg/l for chloride and 100 mg/l for sulfate. Annual average concentrations of dissolved solids are not to exceed 500 mg/l. Acceptable Ph range is 6.5-9.0 and temperature is not to exceed 90 degrees F (320C). 2. Water Quality Data . The United States Geological Survey currently collects water quality data from one location on the Elm Fork near Coppell. Water quality information at this location, State Highway 121, has been collected since 1981. Water quality data for selected days in 1987 is shown on Table III-11. III-29 O€-III '1661 '81 l~Qw~^ON AQ s::lnTIPllJ JY.)llllruJ~l ~sn IllPlsnPlIJ 11lnw!S pUll smJpulll 'SlUllld l~MOd 's::lnTIPllJ ~UllU~l1qtlW lu~wdJn}y.) pUll snQ 'SlUllld lU~WlWll l~lllM~lStlM. pUll l~lllM 'SUOWJll JY.)UM.O-Atp lOJ suonroITddll lJWQns lsnw ~s JO S~IP1llif~1 ~munwwoo nll 'UOnJPPll UJ 'lfW1~d ~PJA\.-W~lsAS lllJWQns 01 JY.)lJD}y.)l ~Q nJM. 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LLZO - >- C I- o _ 00 ...I II. :> Oll: Z~ <0. <C CJ:x: z~ CU) OW 01- ...1- u.U) ::!:Z <Q wU) a:0 I-a: Cl)W :> lI: UJ o~ zo. <:f e!)~ ~U) Ow O!::: OU) ...Jz U.o ...J_ <U) UO oa: ...IW .. + J T'-" .,... z--- o ~ ...J o a: a: <l: f.) z ---..:z: $ ~ "aA1S l:tnHll:t'v' (9 z :> ~ I r'l i u_ 8 ~V11va uo : ~ ~ ~g l.NVtltlV'l. L.~ "J UJ z :> UJ a.. <l: a: (!) o o The North Central Texas Council of Governments is pursuing a Regional Strategy for managing urban storm water quality in order to expedite negotiations with the EP A, coordinate research activities and data analysis, and determine what controls are reasonable for managing urban storm water quality. The Regional Strategy Plan is described in three phases; Phase one - assessment of current storm water conditions, Phase two - development of reasonable and realistic watershed plans, and Phase three - local adoption of five-year storm water improvement programs(Sl). o o o Even more recently, the State legislature amended Section 26.177 of the Water Code to require expansion of the water pollution control and abatement programs for all communities with a population of 5,000 or more inhabitants. The Texas Water Commission has proposed rules which reflect increased regulation of development activities, wet weather monitoring requirements and additional enforcement responsibilities. The proposed rules also require that each community establish an annual fee for the sole purpose of complying with the water pollution control and abatement program. These proposed rules are currently in the review stage. Under the proposed rules, Coppell must submit a Water Pollution Abatement Plan to the State by March, 1993. o o r LJ Q rr U n U o n o n L o n LJ o '1 Ll III-31 IV. FLOOD DAMAGE MITIGATION A Introduction There are several different methods that are useful in reducing or preventing damage from flooding. These methods can be grouped into four broad categories: weather modification; flood prediction; nonstructural and structural flood damage prevention measures; and relief measures. The flood damage mitigation methods are diagrammed in Figure IV-I, and may be used singularly or collectively to reduce flood damages. This chapter summarizes and reviews flood mitigation alternatives and their applicability to streams within the City of Coppell. A more detailed discussion of flood damage mitigation methods can be found in the Fivemile Creek Flood Plain Management Report. (1) B. Weather Modification Weather modification has been somewhat successful in controlling precipitation under certain atmospheric conditions. Future technology may help to control large storms, lessening intense rainfall over large areas and decreasing the destructive power of hurricanes and typhoons. C. Flood Prediction Flood prediction and early warning systems provide time in which to prepare improvised flood defenses and evacuate flood hazard areas. The United States Weather Service utilizes radar to provide flood warnings and predictions. The warnings and predictions are helpful in the planning of flood-warning systems, the executing of improvised flood defenses, and the evacuation of people and property. Flood warnings are made by the National Weather Service. Once the warning is received, key personnel are alerted to the flood situation. These personnel then institute flood water alert procedures, install barricades, and execute other flood response measures. This system has held loss of life from flooding in Coppell to an absolute minimum. D. Nonstructural Damage Prevention Measures Nonstructural damage prevention methods are the management and legislative measures used to reduce flood damage. Some of the more frequently used alternatives are listed. 1. Land Use Zoning One way to prevent flood damage is to keep industrial, commercial, and residential structures from being built in the flood plains. Regulatory measures can be adopted which preserve flood plains for conveyance of the design flood, while obtaining the maximum benefits and productivity from the flood-prone lands. Flood plain zoning limits the flood plain to uses that may withstand flooding without endangering life or valuable property. Flood plains in the City of Coppell are controlled by a Flood Plain Management ordinance. This ordinance is on file with the City and incorporated into the City-WuJe Storm Water Management Study through Appendix A The intent of the ordinance is to preserve the flood carrying capacity of the streams by limiting encroachment and preventing development within the flood plain. All flood plain lands within the jurisdiction of the city are designated as "flood plain management areas" and adjacent developments must fulfill the requirements of the ordinance. IV-I c:- AI " s: r- 0:: 0 2m 0 ::!l~ 0 o I- ~ ~~ -:JJ 3: 0 f) Z " m C; 3: c: :JJ =t m C; <: - ~ - I " ..... 0 ~iD' 0' 6' "0 Z o - ~ :0 m 3 0.3 '"'I m" 3: c~ (1) or- ()"O '"'I 0 m c 0 CD 0 ~ OJ -01- -t !.... -< :r 0 00 :r: _0 ID CD CD ee ... ::!o o '"'I ~c. 50 '0 ~'< 0 ee 0 C (1) Z C/) 0 - - m ~ co- So ~ ~"O '"'I (1) 5" ~- co o. ~~ '"'I - '" CD r-- " o o 0. "'0_ '"'I o o - ::J ee ~:: ~m ~m (1) '"'I I- 3~ (1)(1) :Jc. ... .....- .....- ~ .....- -"'0 o l>> C ..... 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Subdivision Regulations The current City of Coppell Subdivision Ordinance allows for creeks to remain in an open natural condition. Creeks or excavated channels with side slopes of 4:1 or flatter may be platted as part of individual lots with maintenance responsibilities assigned to the adjacent property owner. Channels with steeper side slopes may either be dedicated to the city as a park or floodway management area but could be maintained by a homeowners association or other private maintenance entity. Maintenance can not be assigned to the individual lot owners. If the flood plain land is not dedicated to the city, a floodway easement shall be provided to ensure the protection of these areas for flood conveyanceYJ These land use ordinances are being enforced for the newer developments in Coppell. They help reduce the likelihood of further encroachment into the flood plain which also mitigates flood damage. Thus far, this restriction on the use of private land has been accepted in Coppell. However, there are many older subdivisions that are not subject to the maintenance provisions of the current subdivision ordinance. The establishment of local flood plain ordinances is required by the Flood Insurance Act of December 13, 1973, which qualifies communities to join the National Flood Insurance Program. Only citizens living in National Flood Insurance Program communities are eligible to purchase flood insurance at federally subsidized rates. 3. Construction Regulations The Building Code in Coppell contains general provisions with regard to protection from flooding. The Building Inspector routes all building permits in flood-prone areas to the City Engineer. Each permit is carefully reviewed to determine if the building is located in a flood-prone area. The existing flood plain ordinance requires buildings adjacent to a flood-hazard area to be built with a first floor elevation of one foot above the lOO-year flood elevation based on tplly developed watershed hydrology or two feet above the lOO-year flood elevation shown in the current Coppell Flood Insurance Study. Recommended finished floor elevations are required on final plats of new subdivisions. The adoption of additional criteria for development adjacent to the flood plains of Coppell is investigated in this report. 4. Tax Incentives Tax incentives have been used in other states as a method of discouraging unsuitable development in flood plains. This method of flood damage prevention has not been used in Texas communities. 5. Purchase and Reallocation of Land The municipal purchase of the flood plain is the surest way for a city to achieve control of flood-prone areas. The flood plain may be utilized as a floodway, while providing open spaces, recreational areas, lakes, streets, or wildlife refuges. The Turtle Creek greenbelt park in Dallas is an example of municipally-owned land that is used as a drainage course and a recreational area, and that has improved the quality of life and enhanced property values. White Rock Lake in East Dallas is another example of a significant public park that also provides some flood control by flood water retention. Andrew Brown Park, Grapevine Creek Park, and the Community Park in Coppell are all located primarily in the flood plain. . Cities typically acquire land in the flood plain by three methods: dedication by plat of a new subdivision, purchase, or gift. The "Legacy of Parks" and the "Land and Water Conservation Fund" of the Federal government have contributed substantially to the purchase of flood plain land in Dallas County. The City of Coppell has been deeded flood plain land through the subdivision development process, and has IV-3 v-AI In:Y.>O Aem pOOlJ e ~sn1r.r.}q SMOlJ :){~d uo ~lJ~ ~IUn ~Aeq Aem ~Jn~m q:ms (~)1Y.)ldop-e J~A~U seM pu-e :){~JJ ~nm~A!dJO su-ed Ol ~ndd-e U~qM S~U~An:Y.)lJ~ ~lrarnJO seM ~u-e1I!PJO ~sodOJd ~1U o~~b-eq:>SIP pOOlJ :){~d ~n~J Ol seM lU~l1I! ~1U .~J-e g1I!dOl~A~P 1I! ~-epns snoJA.I~d1II! JO ~gmu~J~d ~Jq-eMOlI-e ~ql lJ1II!l Ol ~un~PJ~ ~l-egn~A1I! g1J!UU-eld u-eqJO JO lU~WlJ-ed~a serr-ea JO AlD ~ql 'SOL61 PJW ~ql Ul .g1I!lU-eld~J JOJ ~lqmJns lOU ~J-e l-eql spop~d gupnp ~sn ~q Plnoqs ~q:>lnm pu-e '~lqJssod se uoos se ~lu-eld~J ~q Plnoqs ~re ~P-eJD .~lqJssod J~A~J~qM ~qJmSIpun lJ~( ~q p(noqs uOJlm~g~A pu-e '~1II!l ~UO hU-e l-e ~J-eq SI l-eql ~J-e pu-e( JO lU~lX~ ~ql ~n~J Ol ~seqd ~q p(noqs uOJl:>nJlSUOJ "uoJSOJ~ pu-e JjounJ ~n~J Ol ~MOll0J ~q p(noqs ~n:>-eJd UOn:>nJlSUOO J~dOJd (E)o~re ~dO(~A~P 1I! J~l-eM WJOlS JO UOn-eJlIY1I! ~ql ~~J:>1I! ~J-e ~l-el~g~A Ol1I! 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Saturated clay soils perform similar to an impervious surface with practically 100 percent runoff. The residents of Coppell voluntarily use many of these watershed management methods which help reduce peak flows of small floods. The mitigation of large floods through watershed management requires more restrictive land use policies or onsite storm water detention. These techniques, their effectiveness, and their costs are discussed in detail in the Fivemile Creek Flood Plain Management Plan. (5) 8. Debris Removal The accumulation of trees, brush, and other debris at bridges and culverts can have dangerous consequences for streams in Coppell. The obstruction of flow causes higher flood stages upstream of a bridge which can overtop the bridge and even cause structural failure of the bridge or road embankment. In Coppell, the Public Works Department is responsible for creek debris removal. The policy relating to floodways and drainageway easements where no structural improvements have been installed is to monitor with budgeted funds, the area to insure compliance to the high grass and weed regulations, address health issues and insure that no vertical structures are constructed which would impact or restrict positive drainage. The City does not take responsibility for debris removal on private property which includes many of the streams in Coppell. The removal of debris that is deposited in a stream or its flood plain is an essential component of any city's flood plain management program. In addition, creeks must be inspected periodically to remove dead trees, or trees whose root systems have been debilitated by erosion. An inspection program of this type should be aimed at prevention rather than reaction. Erosion protection measures should be instituted in areas where significant trees would be in danger of being uprooted by flood waters. The program should also identify and correct areas where siltation could significantly decrease the flood carrying capacity of the stream channel and the bridge's waterway. 9. Inspection of Engineering Works r- The periodic inspection of bridges, culverts, levees, and dams determines if the structures are still functional, thus detecting a flaw in the structure before it fails. Inspections should especially be performed in areas suspected of having potentially unstable soil. (6) In addition to the many bridges and culverts throughout Coppell, there are dams of significant height on the Elm Fork and Stream G4. These dams should be inspected annually. E. Structural Damage Prevention Measures Flood losses can be reduced by the construction of engineering works. Such structural measures reduce flood stages or confine the storm water to a floodway or channel. 1. New Channel Construction or Old Channel Improvements Channelization is a process of excavating a watercourse by widening, deepening, or straightening the stream. These alternatives may be used singularly or collectively to obtain an increase in storm water conveyance. Channel side slopes may be grass lined when the slope is relatively flat and velocities are low, or concrete lined when the slopes are steep or velocities are high. Typically, such alterations of natural channels require significant maintenance. Deposits of sediment may lead to vegetative growth, which causes a reduction in flow if not periodically removed. Channelization is unnecessary wherever an adequate natural drainageway cannot be acquired for flood conveyance. 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Water quality enhancement is sometimes a benefit of flood retarding basins. 7. Raising Ground Elevations The filling of an area within the flood plain to an elevation above the design flood offers a possible solution to flooding. However, the City of Coppell has passed ordinances which discourage encroachment within the flood plain. The filling of an area within the flood plain must be reviewed and acted upon as outlined in the Coppell Flood Plain Management Ordinance. Flood plain reClamation by fill is an alternative plan for some flood plain areas within Coppell. 8. Floodproofing Reservoirs, levees, and channel improvements confine water within the floodway. The purpose of floodproofing is to reduce flood damage to structures and their contents, if flooding is not prevented. (12) A partial list of flood proofing measures includes:(13) . Closure of openings for doors, windows, and vents; . Waterproofing and reinforcement of walls; . Valving of entering utilities; . Protection for immovable equipment; . Anchorage of walls against uplift; . Use of water-resistant materials; and . Removal or raising of contents with short lead time. Floodproofing could be used as a temporary measure to protect any permanent structures in the flood plain, such as park buildings. Floodproofing measures may be used by individuals for protection against floods greater than the design flood. 9. Watershed Management (Structural) The amount of impervious surface is increased by extensive urban development, thus creating greater quantities of runoff and erosion. In some cities, developers, urban planners, and engineers plan structures to detain runoff or increase infiltration, thus reducing the peak discharge in the watercourse. Structural watershed management techniques are designed primarily for new developments, rather than as a corrective measure. A significant change can be achieved only when the majority of buildings and parking lots include retention. The cost of retention to the individual and the city must be weighed against the benefits. Revised building codes and other regulations would have to be enacted to ensure a large-scale implementation of runoff control. An examination of the costs associated with structural watershed management is found in the Fivemile Creek Flood Plain Management Report. (14) The following are structural watershed management alternatives which can be combined or used separately to decrease urban runoff. a. Porous Pavements One method of structural watershed management is the use of porous pavements instead of conventional paving media. Porous pavements enable a portion of the storm water runoff to infiltrate the soil. (15,16) Much of Coppell is characterized by black clays which do not complement porous pavement because of the soil's poor infiltration properties. Water would accumulate on the subgrade, which eventually leads to pavement failures. 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I J,~J " I I.. II I . 1..,-.. o o o [ o II ...... hazardous areas, removal of debris, restoration of streets and bridges, protection and restoration of water and sanitary sewer services, assessment of damages and assisting with traffic control. 2. Flood Insurance Congress passed Title XIII Public Law 90-448, entitled National Flood Insurance Act of 1968, to provide people who already live in a flood plain with low-cost flood insurance. The Texas Legislature passed Article 8280-13 V ACS, allowing Texas cities to comply with this Federal Act, in 1969. Coppell voluntarily complied with the Act, joining the National Flood Insurance Program on June 11, 1975, thus enabling residents to purchase a limited amount of flood insurance. In August of 1989, the first City of Coppell Flood Insurance Study was published and residents became eligible to purchase flood insurance with limits up to $200,000. The Flood Insurance Act of December 31, 1973, Public Law 93-234, requires mandatory actions. In order to remain in compliance, local governments are required to: . . . . submit copies of land-use and control measures; submit maps identifying jurisdictional limits and flood plain areas; submit estimates of buildings and population in flood plain areas; establish a local depository where flood insurance and flood hazard maps will be available for public inspection; and submit a summary of the community's flood history. . The community is also required to adopt and enforce land use regulations which control development in the flood plain. The Federal government provides a Flood Insurance Study, an engineering study that delineates the 1oo-year flood plain and identifies various flood hazard areas. These flood hazard maps are used to set insurance premiums and to assist in planning. (25) The program is administered by the Federal Emergency Management Agency (FEMA). The National Flood Insurance Program requires that flood insurance be purchased for structures flooded by the 1oo-year flood, before home improvement loans or mortgage loans can be obtained from the Federal government or any Federally insured, regulated, or supervised lending institution. Currently there are over 2.2 million policies in force. Since 1978, 350,000 insurance losses have been paid out for a total of $2.5 billion. The premiums for residences vary under the "regular" status, depending on the structure's location within the flood hazard area. The rates vary from $0.25 to $0.60 per year per $100 for structural coverage, and $0.35 to $0.75 per year per $100 for contents coverage. Thus, the insurance premium for a $100,000 home could be as little as $400 per year, including contents coverage. Under a new program called the Community Rating System (CRS), FEMA will reduce flood insurance premium rates for communities that adopt and pursue sound flood plain management principles. These include public information activities, storm water management master planning, drainage system maintenance, and flood preparedness activities. Each community must apply for CRS classification to be eligible for the reduced rates. The Flood Plain Administration (City Engineer) in Coppell applied for CRS classification in December 1990. Due to the sound flood plain management practices undertaken by the city in recent years, the citizens should be eligible for the reduced rates for flood insurance. The National Flood Insurance Program helps to mitigate the cost of damages after flooding has occurred, but it does not correct or prevent existing flood problems. The purchase of flood insurance is one method that will help to mitigate the severity of flood losses to individual property owners. IV-9 V. DESIGN CRITERIA A Introduction In Chapter III, general flooding and environmental information common to the watersheds in Coppell was presented. The general design criteria used to develop the flood plain management plans and specific flooding site alternatives are discussed in this chapter. Final design of the flood control alternatives developed in this study should conform to the City of Coppell's design criteria for paving and drainage projects. Many of the streams studied have the potential to become significant natural resources for the existing and developing neighborhoods of Coppell. The design criteria utilized in the development of flood plain management alternatives for these creeks combine the means of preserving and enhancing a stream's natural qualities with sound flood control engineering. Reaches of streams that are in a natural state and have no flooding problems are designated for preservation. Alternatives are developed to control or eliminate existing and future flooding problems. The City-Wule Storm Water Management Plan should meet a variety of specific objectives in order to insure the flood plain's utility, versatility, and compatibility with urban improvements. This study has taken into account required flood conveyance, the safety of citizens, the visual impact of the creek, the possible recreational uses of the flood plain and other land uses to be derived from the area. The following sections describe specific design criteria utilized in the formulation of these management alternatives. A glossary of terms is included in Chapter IX of this report, to explain the technical terminology. Hydrologic and hydraulic data from the flood plain information phase of the study is included in Appendix E, Summary of Hydraulic Data. B. Floodway Capacity All alternative plans for streams in Coppell should enable the waterway to convey the 100-year design flood for a fully developed watershed. Existing homes and businesses adjacent to the waterway should be free from flooding by the 100-year design flood. Development within the design flood plain is controlled by the City of Cop pel I Flood Plain Ordinance No. 87390, approved October 27,1987 (also cited in Appendix A) and the Coppell Subdivision Ordinance No. 341 approved October 9, 1985,<1) Design standards for the construction of drainage systems should comply with the City of Dallas Drainage Design Manual effective Spring 1990. This manual requires that drainage and floodway easements be provided for all open channels prior to development. (2) C. Channelization The conveyance of natural streams can be increased in some areas by channelization to lower the water surface elevation. Typically, stream channels are straightened and enlarged in this type of drainage improvement and natural flood plains disappear. Recommended channelization is held to a minimum in this study in order to preserve the stream's natural assets. Channelization is considered as an appropriate method of reclamation as long as it is consistent with the recommended storm water management plan and meets the City's drainage design criteria. Channel side slopes will generally meet the design criteria for cut or filled slopes. Slopes that are no steeper than 3 (horizontal)-to-1 (vertical) will be grass-covered. Slopes steeper than 3-to-1 will be protected from erosion utilizing other approved suitable methods. Berms will be constructed to limit slopes to a vertical height of 10 feet V -1 Z - A 'A~M-jO-lqgp lr.lPPl~l ql!M Slr.)l~ lI! ~IQmd~~ ~~ 1-0l-€ jO ~dOIS '~lq!ssod l~^~l~qM '~dOIS ~P!S 1-0l-17 ql!M JY.)l:>rulsuoo ~q ll!M S1Dl~q pU~ ~^~ '~l!S IlmP!^!PlI! 10j UO!l~lOld poog pU~ ~ml~j l~l~M jO mJ!~P ~ql lI! JY.)sn AlUOUllDOO S! UOP~l!D S!lU 'JY.)qSl~l~M JY.)dOI~^~P AlltlJ ~ 10j UO!l~^~I~ poog l~A-001 ~ql ~^oq~ pl~Oq~.IJ jO l~j OMl 10j JY.)mJ!~P ~q ll!M ~ml:>ruls ~~1lL '~~bns poog snOll~S!P ~ 10 ~sd~llOO Sl! 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Ol ~dOls l~lnt~U jO 8u!lln:> ~1lL 'Aln~q l~lnl~U l!~ql jO ~8m~^p~ lltlJ ~J{m Ol '~lq!ssod l~^~l~qM '~l~ ^~ql ~ lJ~1 ~q ll!M ~dOIS ~~1lL '~~ ll~ddo;) ~ql jO ~lnl~j :>!Uoos luwodW! ~~ SJ(U~q ^~P ~lll~lnt~U s,m~lls ~1lL fid pu~ lnJ lI! ~dOIS '0 'sA~!t\l~l~M l~lnl~u ~ql lI! ~nlI!luoo ll!M SMOg MOIl~ql OS 'SJY.)qm~lls ~ql ~^oq~ ld~J{ ~q ll!M SJY.)q ~1~MS ~1lL 'uo!l~~l~ JY.)~ds ~ Ol l~l~~:>~q ~ql soon~l l~ql ~1~MS l~n~ms ~ql 8lI!sooq:> u~ql pu~ suo!l~s SSOl:> l~l~^~S jO OOU~^~^UOO ~ql 8lI!l~l Aq JY.)l~l~s u~q ~^~q sqld~p pu~ sqlP!M mJ!~O 'spoog 8upnp ldoox~ 'Alp lI!~m~l All~1~U~8 ll!M ~1~MS S~lO 'Jl~Sl! m~llS ~ql Ol 10 ~8ppq Ol SUO!l~l~ll~ ~l~1I!WTI~ Ol su8!~p JY.)SOdOld lI! JY.)l~lOdloolI! ~q U~ ^~1lL '~~l:> Ol l~n~l~d Sl~l~M poog ^~^UOO Ol ~ld poog lI! ~l~^~X~ ~q ^~m ~1~MS Mon~qs F. Bridges 1. New Bridges This study recommends that a distance of two feet between the maximum design water surface elevation and the lowest beam of the bridge be maintained for all new bridges. . This requirement is for safety reasons as well as flood control. The two foot fr~ opening helps prevent floating debris from collecting on the bridge or causing an obstruction which could create upstream backwater flooding and endanger the structure itself during an occurrence of the design flood. No increase in design water surface elevation is also a requirement for design of new bridges. One method of maintaining the lOO-year flood elevations is to span the entire flood plain. This method can be cost prohibitive for major thoroughfare crossings. These crossings usually include a shorter bridge span with a minimal amount of upstream and downstream channelization. 2. Existing Bridges Existing bridges may be lengthened to permit widening of the channel or openings enlarged to increase conveyance area. This modification reduces backwater and lowers the channel water level upstream of the bridge. Flooded bridges cannot all be replaced at the same time because of limited City funding. The replacement of flooded bridges must be undertaken as part of a city-wide, long-range bridge replacement plan. Criteria for the development of a long-range plan are discussed in Flood Plain Management of Cedar Creek. (6) Criteria such as structural soundness and adequate traffic capacity must be considered as well as flooding problems, in the determination of a bridge replacement plan. An interim alternative to bridge replacement is the installation of a flood warning system to inform and alert motorists of hazardous crossings. The Texas Supreme Court has ruled that cities and counties can be held liable for the failure to warn motorists of flood hazards. (7) On lightly travelled roads, passive warning systems may be used. These should include a warning sign such as "Beware of High Water" and a gage with easy to read depth markings. An active warning system consisting of an electronic water level sensing device should be used on the more heavily travelled roads. In general, guardrails should be included on the downstream side of the structure and in the overbank where velocities exceed three feet per second and the water depth over the top of road exceeds one foot. In this study, overtopped crossings are rated by a formula equal to the depth of flow in feet times the velocity (feet per second). Crossings with ratings greater than 9 are considered dangerous and should have the highest priority for correction. Crossings with ratings between 4 and 9 are unsafe and should also have a high priority for correction. Crossings with ratings less than four constitute minor flood hazards and should have a low priority for improvemenL A zero rating would indicate no flood hazard. All overtopped crossings should be made safer by installation of guardrails and warning systems. A schedule of crossing improvements must also be initiated beginning with the most dangerous as determined by the safety ratings. Table V-I contains the safety ratings for all flooded stream crossings in the Coppell study area. The dimensions, lengths and elevations for bridges recommended in this report are to be used as design guidelines only. Field conditions, detailed in final design, may dictate changes to the indicated dimensions. Bridge hydraulics should be checked after construction documents are complete and for the 'as-built' bridge condition. V - 3 P - A At!-lO!-lcl ~!H - ;)JWlln (z) At!-lO!-lcl1s;lqS!H - snOl;)SUllG (t) (z)v'5 Z'E L'l poo~ ;)111lS IJ WVIDllS (z)5S'v SZ'E n poo~ ;)111lS 6'E E n poo~ rr:xIdOJ HJNWH GOOMNOllOJ 8'Z 5'Z n poo~ rr:xIdOJ lG WVIDllS VS'O 50'Z U>'O poo~ ;)lOOW U"O !n>'l SZ'O poo~ \ooq:>s Pql;)H 90 WVIDllS LL'l LS'l En ;)Ull'l !lSJ.IllJ lE'Z vl"S 51>' ;)^!lG l;)ll11J 50 WVIDllS 1>9'1: 19'1: 10'1 :J^!lG SJ1!H Sumo~ vvo WVIDllS (z)5n 6v'E 6n :J:>l1\cl1smqpooh\ (z)LO'5 6Z'E 1>S'l poo~ \ooq:>s \;)q1;)H (z)%"1> 99'E 6n pll0~ ~=MOp11;)W 1>0 WVIDllS ES'l %"Z 59'0 poo~ ~:J;)l:>MOp11;)W ED WVIDllS (z)9' L O'V 6'1 pll0~ pq1;)H (t)Z'ZZ 0'9 L'E poo~ rr:xIdOJ (t)V'91 8'L 1'Z poo~ \ooq:>s pq1;)H 10 WVIDllS (z)99'L 89'1: 98'Z poo~ \;)q1;)H EI>'E En 85'Z ~ W;)1s;lMq1nos '1Il SJnOl 'lS 6L' 58' E6' poo~ ;)UJj l\;)H )l'3ffi1J '3NIA'3~D (l:J;)J) poo~ l;)^O SUJ1~ At;)J11S (OOJ) At!:>O\;)A q1d;)G ;)A!l:>;)JJ'3 SUJ!l!lOlJ ^11MpOO~ SDNLLVlI AJ&ilVS SDNISSOll:J WWlLLS mu()()'U loA TIHV.L G. Culverts Both the inlets and outlets of culverts are designed to be submerged during the design flood. The roadway must be two feet above the design flood water surface at the culvert's inlet. New culverts may be added beside existing culverts at crossings to lower the water surface. Use of existing culverts, in conjunction with new ones, reduces construction costs. The most economical design is normally obtained by sizing the culverts so that the upstream water surface is two feet below the roadway. Maintenance of the design water surface at a high level helps to temporarily store water upstream of the culvert, thus reducing the peak flow downstream. Like bridges, culvert hydraulics should be verified both after design and after substantial completion of construction. Safety ratings for flooded culvert crossings inventoried during this study are also shown on Table V-I. H. Parkways A parkway is a thoroughfare or local street paralleling the stream which creates a buffer zone between the flood plain and development. The parkway provides a border for the area subject to flooding, preventing future encroachments into the flood plain. They facilitate local traffic conveyance while providing a leisurely route interconnecting the parks along the flood plain. The parkway, with its vistas and ecological assets, can greatly enhance neighborhoods in Coppell by accenting a quiet park-like atmosphere. Parkways are aligned by locating the creek-side, parkway right,.of-way line along the design flood inundation line. The parkway minimum grade should be not less than one foot above the design flood elevation. Existing streets can be utilized as a part of the parkway system. The incorporation of existing streets into the overall system will preserve existing neighborhoods and institutions while providing access to open space. The construction of new thoroughfares within the city is regulated by the Master Thoroughfare Plan, hereinafter referred to as the Thoroughfare Plan. The thoroughfare plan as revised in 1990 is used in this study. (8) This plan classifies the thoroughfares by type and establishes minimum design standards for each classification. The Thoroughfare Plan includes a route location map and route descriptions for secondary, major, and freeway thoroughfares. Also included are pavement sections and minimum design standards for each class of thoroughfare. Parkways are designed in accordance with this plan, therefore new parkways through undeveloped land are compatible with future development. All intersections are 9O-degree intersections at normal grade, which facilitates direct access to adjacent properties. The parkways are designed as scenic drives and will be delineated by special parkway signs. Parkways may also incorporate elements of the City's Streetscape Plan such as edge treatments along the parkway with accent trees similar to the secondary image zones. (9) I. Land Acquisition Undeveloped land within the flood plain may be acquired through dedication, voluntary sale, or by condemnation. In most cases, flood plain land is not recommended for purchase in this study, unless it has a secondary benefit, such as recreation or unique natural vegetation. Houses are considered damaged only when the design flood elevation is above the house finished floor elevation. House purchases and subsequent relocations are held to a minimum by considering use of structural flood prevention alternatives. If there is no economical structural flood control solution, the house should be acquired by voluntary purchase, allowing residents to remain until they are ready to sell their property. 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This report shows only 15 occupied residential structures inundated by the 1oo-year flood along the 25 miles of streams studied. All but five of these residences are in older areas of town which may be expected to re-develop. Twenty-four streets on eleven streams are also overtopped by floodwaters. A complete list of these stream flooding sites is found in Chapter III, Table III-B. An inventory of all existing structures crossing the streams is contained in Appendix D. Eleven erosion problem sites along streams in Coppell were also identified in Chapte,r III, Table III-lO. These sites are prevalent in the rapidly developing areas of the city. Alternatives such as bridge, culvert and channel improvements are investigated to solve these stream flooding and erosion problems indicated on Figure III-4. Other local drainage problem sites, not directly related to a natural stream channel are discussed in Chapter VII. Currently, the majority of the flood plains in Coppell are restricted to private open space with the largest single use being Riverchase Golf Course along the Elm Fork of the Trinity River. A limited number of parks and athletic fields are found. However, a significant amount of the flood plain remains undeveloped. The real challenge of this study is one of preserving and protecting these remaining undeveloped scenic and environmentally significant reaches of the stream. The natural channels and wooded open spaces can be significant contributors to the quality of life in the neighborhoods that soon will develop in Coppell. To accomplish this task, alternatives such as parkways, bike and bike trails, and open space preserves are investigated. Criteria for the preservation of the natural valley storage within the stream system are also presented, and all key elements in preventing increases in downstream flooding due to future development. Construction cost estimates for all alternatives are included. These estimates of probable construction cost are based on April 1990 unit prices compiled by the City of Dallas Public Works Department, unless otherwise noted. The total estimated costs include construction, engineering design, surveying, geotechnical testing and easement documentation. Easement acquisition costs are not estimated. Evaluation of the alternatives and final recommendations are included. Implementation of the recommended City-Wide Storm Water Management Plan will be discussed in Chapter VIII. Delineation of the 1oo-year flood plain for a fully developed watershed is shown on the Plates in Appendix F. B. Specific Stream Flooding Sites 1. Grapevine Creek Grapevine Creek is a tributary of the Elm Fork of the Trinity River. The creek enters the City of Coppell at the southeastern Coppell/lrving corporate boundary under IH-635 and flows in an easterly direction for six miles along portions of the southern border of the city to its confluence with the Elm Fork. Under existing channel conditions, the 1oo-year discharge (fully developed watershed) will flood three residences in the vicinity of Bethel School Road and Hawk Lane. In addition, Belt Line Road, the St. Louis and Southwestern Railroad, the Bethel Road approach, and Bethel School Road are inundated by the 1oo-year flood. Severe bank erosion is also occurring downstream of IH-635 and in the reach from Denton Tap Road to Moore Road. Grapevine Creek is the most developed of the three major streams which traverse the city. Two major reclamation projects; the Irving Flood Control District Section III, near the confluence with the Elm Fork, and the channelization downstream of IH-635, have been completed in the last ten years. 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'p~o'M d~~ U01U~a 01 p~o'M ~lI!'1 lI~g mo.IJ q:>Wl ~ql lI! lSPC~ OSI~ Slu~mdoI~^~P I~!lU~P!S;}l snol~mnN A proposed realignment of Belt Line Road and Grapevine Creek dated July, 1988 was supplied by Ginn, Inc. This alignment was not utilized for the alternatives evaluated in this study due to the presence of 2 - 90 degree bends in the proposed Grapevine Creek channelization. The proposed bridge in the two alternatives above assumes that Belt Line Road will remain in its current location. The Belt Line Road improvements (Alternative L) are the recommended design solution to remove the homes on Bethel School Road from the flood plain. The minor amount of upstream channelization is required to control erosive velocities. These improvements are estimated to cost $560,000. Development pressures in the commercially zoned area downstream of Belt Line Road may result in further consideration of the channelization alternative but it is not included in the flood plain management plan shown on Plate 3-2. Any channelization proposed in the future should be required to compensate for valley storage loss to ensure that the existing Irving Flood Control District levees are not overtopped. b. Erosion Downstream of Denton Tap Road/Meadowcreek Road Severe erosion has degraded the channel downstream of Denton Tap Road. Numerous complaints have been received along the south side of Meadowcreek Road from property owners with lots backing up to Grapevine Creek. In some areas existing retaining walls have failed and portions of fences and back yards have been lost. The creek meanders through this reach and narrows significantly at each bend. Velocities for the 100-year flood are highly erosive ranging from 8 to 13 feet per second. The channel banks are 10 to 15 feet high and nearly vertical. In several areas along the south side of the creek new homes have been constructed with no set back from the top of bank. Gabions have been utilized with some success in a few of the meanders, but there is evidence of undermining beginning along the downstream edges of several of these structures. In spite of the construction along the banks of the channel, the area remains very scenic and environmentally significant. Blue gill, large mouth black bass and a variety of birds including red- winged black birds, belted king fishers and blue jays were spotted during the field reconnaissance of this reach of Grapevine Creek. To aid in the preservation of this area, the recommended design solution to the erosion problems includes the identification of critical areas along the bends of the creeks. Straighter reaches and areas where erosion is not threatening private property should be left natural. These critical areas are shown on Figure VI-I. Structural stabilization is required along the full length of these bends extending 100 feet downstream. In areas such as the 100 block of Meadowcreek Road and under the east aerial sewer crossing, the existing retaining walls are failing. These should be tom down and replaced extending the full length of the bends. Where gab ion structures currently exist, the edges should be monitored for failures and repaired or extended immediately, if necessary. Due to the high velocities and steepness of the existing creek banks concrete retaining walls are recommended. These should be structural retaining walls with adequate foundations such as drilled piers. Large rock rip rap or gabions can be placed along the toe of the walls to control creek bed erosion. Decorative facings could also be added to these walls to enhance the beauty of the channel. Figure VI-2 show several conceptual treatment plans for the creekside embankments which could be incorporated into final designs. The estimated probable cost of these improvements, not including decorative facings, is $600 per linear foot. This correlates to approximately $60,000 for an average size creek lot. The estimated probable cost for the proposed erosion protection in the critical areas shown on Figure VI-I is $1,350,000. Final design of this erosion control should include detailed surveyed cross sections where severe erosion is occurring since these areas may have altered significantly since the topography used in this study was prepared in 1985. VI-3 rIA 'SU-eld UO!PlUlSUOO uo At!:) ~ql Ol Slu~m~l'elS .s~JlIlI-eH PloH. ~P!^Old . 'U!-eld poolJ ~ql U! Sl~!d 10 sn-eM 10j sn-el~P PU-e SIsAI-eU-e I-eml:>lUls ~P!^Old . 'SUO!l!PUOO ~sn Pu-eI ~dOI~A~P AIItlJ 10j ~npOI~A pu-e SUO!l-eA~I~ ~-eJlns l~l-eM l~A-OOl PU-e -Z MOqS . '~.I!n]y,)l J! 'I01lUOO UO!SOl~ ~SOdOld UO sn'el~P ~U!pnpU! 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'" . .<~z<.. /""<~,'i,..::'- ~ ~-:'~"''\. j '" ", -.........y- :!: .~ AKE DRIVE ;'; " .,,/ ~ &~ en () ~ r rrI c..> Z a a "11 ~ -l "/ 0) / a c... a '" OG) O:a Z:l> ~"U :am O~ r-Z." m_ OoG) :a:aC =im:a -mm O~< ~ - r-ml :a""'" ~O :a en m_ :1>0 tnz I ! mo ><:0 en-i -i- -0 z)> G>r m)> :0:0 Om en)> -en o z () o Z -i :0 o r /' c: -Z C ~/ /0 / Z ..... ....~.-...- " \ r m G) m z o V"'c., .. '-', r"', / " \ I (/ / '" ! . $,: / " r- CONCRETE WALL ROCK RIPRAP TERRACED WALL ROCK RIPRAP DRY RIPRAP GROUTED RIPRAP CONCRETE RIP RAP (DECORATIVE FACING) FIGURE VI-2 GRAPEVINE CREEK CHANNEL STABILIZATION ALTERNATIVES channelized portion of the stream including the Freeport Parkway bridge. The condition in the approval was that a nine foot high concrete drop structure be constructed approximately 1,000 feet upstream of Freeport Parkway to control erosion. FEMA and the City of Coppell both require that the drop structure be constructed prior to revision of the regulatory flood plain maps. Velocities in this reach of Grapevine Creek range from 13 to 16 feet per second causing continuous erosion as the enlarged channel attempts to migrate upstream. The eroded area now extends upstream of IH-635 and into the City of Irving. Two design alternatives were investigated to control this erosion. i. Proposed Drop Structure Downstream of IH-635 The first alternative consists of a nine foot tall concrete drop structure with concrete erosion protection upstream and downstream. An earthen channel with 4:1 side slopes and bottom widths varying from 70 feet to 100 feet is also proposed for about 470 feet downstream of the proposed drop structure. This proposed design was submitted to FEMA in May of 1986. As a result, approval of the concept in the form of a Conditional Letter of Map Revision dated August 18, 1987, Case No. 86-06-47R, was issued for this reach of Grapevine Creek. These improvements were tested in the updated Flood Insurance Study and flood plain management hydraulic models and were found to be in compliance with the City of Coppell's Flood Plain Ordinance as well as FEMA's criteria. The estimated cost of these improvements is $410,000. ii. Proposed Check Dam Downstream of IH-635 The second alternative solution to this problem utilizes a 5.5 foot tall check dam located 800 feet upstream of Freeport Parkway. Concrete erosion control upstream and downstream of the proposed structure is included. Approximately 400 feet of channelization (180 feet BW; 4:1 SS) is required downstream of the drop structure. A transition and erosion control is also required between the drop structure and the downstream face of IH-635. The estimated cost of these improvements is $400,000. These two design solutions are comparable in both cost and effectiveness. The second design solution with the 5.5 foot check dam is shown on Plate 3-7 since this is a smaller structure and better accounts for the erosion which has already occurred. Final design of this erosion control structure may require further modifications to the proposed check dam or drop structure to match existing grades. The channel is continuing to erode at an alarming rate and it is recommended that the city contact the developers along this reach of Grapevine Creek requesting that they initiate the design and construction of this structure as soon as possible. Since the city is not allowing development in the reclaimed areas of Grapevine Creek until this structure is completed, all adjacent property owners in this reach should be encouraged to participate. f. St. Louis and Southwestern RR to Southwestern Drive One drainage and flood plain complaint along this reach of Grapevine Creek was investigated. The property owner on the east side of the creek had several concerns about existing and future development. South (upstream) of Southwestern Drive the creek has been channelized and a large commercial development is currently under construction. This downstream property owner is concerned about increased flood flows from the commercial development. All design water surface elevations shown in this report are based on the fully developed land use scenario, thereby accounting for future urbanization. Generally speaking, this piece of property can also be developed to its ultimate land use as long as the criteria of the Coppell Subdivision and flood plain ordinances are met. The City of Coppell Future Land Use Plan shows this piece of property as designated for mixed use-special use as a transition area between the adjoining light industrial and residential land uses. VI-8 In addition, this property owner also complained of erosion from offsite drainage and the accumulation of trash along the railroad. It is recommended that city staff perform a field reconnaissance of the railroad easement throughout the city and, if necessary, send a letter to the railroad requesting they clean and maintain their property. The property owner immediately east of the subject property could also be contacted about the erosion problem. However, the city has little or no reSponsibility for this problem which is on private property. g. Southwestern Drive Improvements to Southwestern Drive from Freeport Parkway to Denton Tap Road have been designed. Halff Associates determined the hydraulic size of the bridge structure crossing Grapevine Creek as part of a separate study for the City of Coppell. This study entitled Flood Plain Study on Grapevine Creek: Southwestern Boulevard to IH-635 also includes a proposed rail crossing. These proposed structures are included in the Flood Plain Management Plan for Grapevine Creek as future structures and shown on Plates 3-6 and 3-7. 2. Stream G 1 Stream G 1 is a tributary of Grapevine Creek which flows in an easterly direction for a distance of 1.1 miles. The study reach is from the intersection of Freeport Parkway and Bethel Road, where it outfalls from an existing 10 x 5 foot box culvert, to its confluence with Grapevine Creek, approximately 200 feet downstream from Bethel School Road (also called Harris St.). Under existing channel conditions, the l00-year flood (fully developed landuse) inundates the crossings at Bethel School Road, Coppell Road, Bethel Road, and Freeport Parkway (see Appendix D). Bethel School Road and Coppell Road both have safety ratings in the dangerous category (Table V-I). Cul-de-sacs at Anderson Avenue and Mitchell Street are also flooded. Six residences between Mitchell Street and Loch Lane and several storage buildings also show to be within the l00-year flood plain. Complaints of flooding and erosion problems have been received from residents along Loch Lane and Mitchell Street. a. Bethel School Road (Harris St.) Bethel School Road crosses Stream G 1 approximately 200 feet from its confluence with Grapevine Creek and is overtopped by the l00-year flood by 2.1 feet. The recommended design solution to this problem involves channel improvements (20-foot BW; 3:1 side slopes; grass lined) for 50 feet downstream of Bethel School Road and 30 feet upstream, the installation of a proposed bridge, and raising of the road surface by six feet to an elevation of 498. This road embankment would tie in to the existing Bethel Road bridge over Grapevine Creek and will also relieve the intersection flooding in this area. The estimated cost of these improvements is $555,000. A detail of this area is shown in Figure VI-3. b. Coppell Road Coppell Road crosses Stream Gl at Stream Station 43+80, approximately 300 feet north of the intersection of Coppell Road and Bethel Road. The l00-year (fully developed watershed) flood overtops existing Coppell Road by 3.7 feet. The recommended design solution to this problem includes an improved earthen channel (35 foot BW; 3:1 SS) for 250 feet downstream of Coppell Road, the installation of a proposed bridge and raising the road surface by 7.5 feet to an elevation of 511.5 as shown on Plate 3-6, Appendix F. The estimated cost of these improvements is $488,000. This structure is sized for future Coppell Road as shown in the City of Coppell "Thoroughfare Plan." VI-9 W I- Z w :E w Ie; a:1-a: <(3:Cl. WW:E >;-Zo o-W O....JO T"""ZZ WOW W-oo::: I-!ci:":: OO:E ZZO W::>frl OZa: . , lit z o - ~ Q Z :;) o LI. I- CJ) - I- Q. C ( ~ > w a: ~ " - u.. ci a: ...J~ OZ"'" OW" J:~~ OW~ en>...... ...J 0 W w a: a: J: Q. ~ ~:Een w- m \ c. Erosion Downstream of Coppell Road (Mitchell Street) Stream G 1 is experiencing considerable erosion on its southern bank at a point approximately 250 feet downstream from Coppell Road. A small retaining wall has begun to fail in this area and severe scour is occurring behind the remaining wall. Ultimately the Coppell Road channelization mentioned earlier will correct this problem. However, in the interim the recommended design solution is to remove the existing retaining wall and install grouted rock riprap on the southern channel bank at this location. The estimated cost of these improvements is $5,000. Additional erosion of a less severe nature is occurring along the bend immediately downstream of the retaining wall through the existing footbridge near Stream Station 40+00. Some erosion is also occurring near the footbridge on the north side of the creek. Additional improvements to address this erosion involve extending the grouted rock riprap along the south bank from the existing retaining wall to just downstream of the footbridge as well as grading along the north bank to a 15 foot bottom width channel with 3:1 side slopes. Some grouted rock riprap will also be required on the northern bank near the footbridge. The estimated cost of these additional improvements is $17,000, which brings the total cost of interim erosion control in this area to $22,000. The scope of this proposed erosion control is shown on Figure VI-4. d. Loch Lane Stream G 1 runs parallel to Loch Lane between Coppell Road and Bethel Road causing erosion and flooding problems to several home owners. Two residences are in the l00-year flood plain (see Plate 3-6, Appendix F). Numerous alternatives were considered to alleviate these flooding and erosion problems along Loch Lane. These are listed below. i. Channelization of Downstream Reaches Due to the high flood water depths downstream of Coppell Road in the vicinity of Anderson Avenue, extensive channelization of the lower reaches of Stream G 1 was considered. However, this alternative was rejected as being too disruptive to this environmentally significant reach, especially within the park located near Anderson Avenue, to merit further detailed analysis in this study. li. Detention Storage There are undeveloped sites upstream of Loch Lane which could potentially be used as storm water detention sites. Detention could result in substantially lower discharges downstream along the entire tributary. In order to implement the detention alternative in this area, undeveloped land not currently in the flood plain would have to be purchased and excavated to create a detention site. Compared to other alternatives, the cost of this alternative would be excessive as a solution to the Loch Lane flooding problems or other flooding problems along Stream G 1 because of high property values in the area. Therefore, storm water detention as a recommended city project on Stream G 1 was eliminated from further consideration. lii. Voluntary Purchase of Flooded Structures The city could volunteer to buy the flooded structures and the owners could choose to relocate. While this option is a viable one, it is often not acceptable to the residents who live in flood prone areas, such as Loch Lane. In light of the potential for future redevelopment of this area, voluntary purchase and restrictions on additional construction in the flood plain may at some future time become feasible. VI-ll SEE PLATE 3-6 FOR ADDITIONAL I MATON ON S AM G1 o 200 , . SCALE IN FEET X 515.4 FIGURE VI-4 STREAM G1 EROSION DOWNSTREAM OF COPPELL ROAD iv. Channel Improvements near Loch Lane Several channel improvement alternatives were considered in the immediate vicinity of Loch Lane. The basic alternative involved the construction of a grass lined channel with a 25 foot bottom width and 3:1 side slopes from Coppell Road to Bethel Road. Other alternatives investigated included improvements to the Coppell Road culvert and channelization downstream of Coppell Road. These other additions to the basic alternative were costly relative to the very slight reduction in flooded area achieved and are, therefore, not recommended for the purpose of addressing the flooding problems along Loch Lane. Improvements to Coppell Road are required, however, to alleviate the flooding problems which exist at Coppell Road itself (see Section 2.b.). A concrete lined channel alternative was also developed to confine the 100-year flood within the channel banks. The estimated probable cost of this alternative ($209,000), however, is excessive to solve the minor flooding in the area. The recommended design solution involves the construction of a 25 foot bottom width grass lined channel with 3:1 side slopes from Coppell Road to Bethel Road. One garage structure would remain in the 100-year design flood plain but inundation would be less than half a foot. This alternative also provides approximately one additional foot of freeboard for the living area finished floors of the homes along Loch Lane. In addition, the prqposed channel would be easier to maintain. This recommended alternative is shown on Plate 3-6 in Appendix F. This channel design was also the least expensive alternative considered at an estimated cost of $31,000. A 10 foot wide concrete pilot channel could be included for maintenance purposes and would cost an additional $44,000. e. Unnamed Tributary of Stream G1 (N.C.H. Tract) In light of the existing flooding problems on Stream G 1, questions have been raised about the course of the drainage from a large tract immediately north of Bethel Road. This tract and some additional upstream property is currently drained by a small tributary of Stream G 1 which passes through a residential lot at the end of the Loch Lane cul-de-sac. Its confluence with Stream G1 is located approximately 100 feet upstream of Coppell Road. Detention as a part of the development of this site may be advantageous to both the city and the developer in this area. The existing flooding problems along Loch Lane preclude the diversion of any of this tributary flow to the south along Bethel Road. Therefore, the drainage must either follow its existing path through a private residential lot or be routed north then east to Coppell Road and into Stream G 1. Although there have not been any flooding complaints from the current resident, storm water runoff from the developed site would probably cause significant inundation of this lot and possibly the home. The developer of the N.C.H. tract would have to install an expensive underground system and obtain an easement from the property owner. Detention on the N.C.H. site could significantly reduce the flow through this private property and may result in minor reductions in flooding at Coppell Road and downstream on Mitchell Street. The recommendation for this area is that development in the vicinity of sub-area G-1- 4 as shown on Plate 2, Appendix F should be carefully monitored by city staff. Drainage plans which route any of this storm water runoff south into Stream G 1 upstream of Bethel Road will aggravate existing problems and should not be allowed. Development of detention storage on this tributary of Stream G1 should be encouraged. VI-13 f. Bethel Road Bethel Road crosses Stream Gl near stream station 51+00, approximately 750 feet east of the intersection of Bethel Road and Freeport Parkway. The lOO-year flood overtops existing Bethel Road by 1.9 feet. Residents along Loch Lane report that Bethel Road was overtopped twice in 1990. The recommended design solution to this problem is to install four 10 x 10 foot box culverts and to raise the existing top of road to elevation 512, an increase of three feet. The estimated cost of these improvements is $426,000. The Bethel Road improvements are shown in red on Plate 3-6. g. The Intersection of Freeport Parkway and Bethel Road The hydraulic analysis performed in this study indicates that Freeport Parkway is inundated by the lOO-year flood by less than 0.5 feet. Drainage complaints on file with the city indicate that the intersection of Freeport Parkway and Bethel Road is also subject to flooding. The recommended design solution to these problems involves the construction of an earthen channel (50 foot BW; 4:1 SS) on Stream G 1 from Bethel Road to Freeport Parkway. In addition the bar ditch which runs along the north side of Bethel Road should be regraded and enlarged. The inadequate capacity of this roadside ditch apparently contributes to the frequent street flooding. The estimated cost of these improvements is $69,000. h. Evaluation of Drainage Improvements Upstream of Freeport Parkway In 1988, extensive improvements were made to the drainage system south of Bethel Road and west of Freeport Parkway. The improvements consist of a single 10 x 5 foot box culvert immediately upstream of Freeport Parkway and a 20 foot bottom width earthen channel near Royal Lane. The existing 10 x 5 foot box culvert is inadequate to carry the fully-developed lOO-year flood discharge of 2625 cfs. .The original design called for 2- 10 x 5 foot box culverts in order to carry the existing condition 50 year discharge of75l cfs, which is approximately one-third ofthe fully developed lOO-year discharge. Only one of the two box culverts was constructed. The fully developed lOO-year discharge shown on the Bethel Road Drainage Improvements construction plans is 2,123 cfs which is less than the 2,625 cfs developed in this study. The smaller number should not be used since it is based upon calculations utilizing the rational method. The City of Dallas' Drainage Design Manual restricts usage of the rational method to areas less than 130 acres. The drainage area above Freeport Parkway is 379 acres. The earthen channel near Freeport Parkway was also designed based upon the 50 year flood discharge (existing land uses). This channel also does not have adequate capacity to carry the lOO-year design flood discharge and maintain the minimum channel freeboard which is required by the City of Dallas' Drainage Design Manual. Therefore, it is recommended that, prior to the construction of the second 10 x 5 foot box upstream of Freeport Parkway, a detailed evaluation of the watershed be undertaken and a revised design be developed based upon the lOO-year (fully developed watershed) discharge as calculated by recommended methods outlined in the City of Dallas' Drainage Design Manual. 3. Stream G2 and Stream G2A Stream G2 is a tributary of Grapevine Creek. It joins Grapevine Creek approximately 250 feet upstream of the Denton Tap Road bridge over Grapevine Creek. The stream flows from the north beginning approximately 1500 feet north of Bethel School Road at a storm sewer outfall. The storm sewer VI-14 drains the northern most part of the Shadow Ridge Estates Subdivision. A concrete pilot channel (5 foot wide with curb) extends from Bethel School Road north to a point about 300 feet downstream of the storm sewer outfall. Two other storm sewer outfalls from the same subdivision occur upstream of Bethel School Road. These storm drains connect via concrete flumes to the small concrete pilot channel. The area north and east of the Shadow Ridge Estates development is presently undeveloped. The runoff from this undeveloped area flows into the channel behind 252 Plantation Drive. The channel is primarily grass lined in this area with scattered trees located on the higher banks. Downstream of Bethel School Road the channel is wooded, meandering, and has many changes in cross sectional shape. About half way from Bethel School Road to the contluence with Grapevine Creek, a tributary (Stream G2A) from the west flows into Stream G2. Downstream of this confluence the channel has been realigned due to encroachments created by the widening of Denton Tap Road. At one point the channel becomes grass lined with stone rip rap where the Denton Tap Road encroachment was the greatest. However, the remaining portion of the channel is overgrown and there are many fallen trees near the contluence with Grapevine Creek. The only recorded drainage complaints on Stream G2 deal with erosion of the channel banks. This erosion is primarily on the east side where runoff from the undeveloped land enters the channel. When this area is developed, a storm sewer system will probably be installed and adequate protection should be provided as part of this future development. However, in the interim the runoff flows over the channel banks and is eroding the bank as it enters the channel. The most economical short term solution is grouted rock riprap from the top of bank to the concrete pilot channel for a distance of 150 feet. The estimated cost for this protection is $26,000. Dry rock riprap could also be utilized for an estimated cost of $16,000. This is a less expensive alternative but may require more maintenance. In addition, some erosion is occurring around the storm sewer outfalls from Shadow Ridge Estates. These areas are also overgrown and in need of maintenance. During the design phase for the above recommended erosion control the outfalls should be reviewed and erosion control included in the construction plans, if necessary. This reach of Stream G2 from Bethel School Road to Plantation Drive should then become part of a regular city-wide creek inspection and maintenance program to ensure that the erosion control remains functioning, as designed to eliminate future citizen complaints. 4. Stream G3 Stream G3 is a tributary of Grapevine Creek which flows approximately 1500 feet in a southerly direction between Arbor Brook and Lea Valley Lanes. A 48-inch diameter storm sewer pipe from the upstream portion of the watershed outfalls at the beginning of the stream. Meadowcreek Road crosses the stream's path approximately 400 feet upstream of its contluence with Grapevine Creek. Several fences cross the stream's path upstream of Meadowcreek Road. The overbank area of the stream is primarily well maintained backyards with dense to moderate tree areas. Dense trees are found downstream of Meadowcreek Road as the stream enters the Grapevine Creek flood plain. A review of the loo-year flood plain on Stream G3 found no flooded structures. Finished floor elevations were obtained from the plat of the Northlake Woodlands Addition, dated May 1974. However, there is frequent nuisance flooding of several backyards upstream of Meadowcreek Road. This flooding, coupled with the overtopping of Meadowcreek Road by the loo-year flood (fully developed watershed), precipitated the design of culvert improvements. These improvements involve removing the existing 60 inch pipe and installing one 6 x 5 foot box culvert at an estimated cost of $29,000. The proposed VI-15 improvements will remove Meadowcreek Road from the 100-year flood plain and will significantly reduce the frequent flooding of the backyards. The 2- and 100-year flood plains with this improvement are shown on Plate 3-4, Appendix F in red. 5. Stream G4 and Stream G4A Stream G4 is in the eastern portion of the City and flows in a southerly direction 4400 feet from its point of origin at Willow Springs Road to its confluence with Grapevine Creek downstream of Meadowcreek Road. Triple 30 inch diameter storm sewer pipes discharge into the stream at the downstream face of Willow Springs Road. The stream has a six foot wide concrete pilot channel with 4:1 grass sideslopes from Willow Springs Road to Woodhurst Drive. A park and lake area exists between Woodhurst Drive and Bethel School Road. The design water surface elevation in the lake is 496 feet msl. Water is impounded in the lake by a dam approximately 240 feet upstream of Bethel School Road. Excess storm water runoff overflows into two special ten foot inlets which connect to double 36 inch diameter storm sewer pipes outfalling downstream of the dam. Stream G4A is a tributary of Stream G4 and flows in a southwesterly direction approximately 900 feet from its point of origin at Bethel School Road, crossing Rolling Hills Drive before joining Stream G4. The stream reach between Bethel School Road and Rolling Hills Drive consists of well maintained backyards with moderate tree stands in the overbanks. In addition, clusters of trees exist in the channel within this reach of Stream G4A Downstream of Rolling Hills Drive the stream is straight and clean with well maintained overbanks. The 100-year flood plain was delineated on Stream G4A and no flooded structures were found to exist. Rolling Hills Drive is overtopped during the 100-year flood but is not a severe hazard. Therefore, no improvements along Stream G4A are recommended as a part of this study. The reach of Stream G4 upstream and downstream of the confluence with Stream G4A is straight and well maintained by the adjacent property owners. However, several fences cross the stream's path and moderate to dense tree stands exist near and in the stream. A 6 x 8 foot box culvert conveys storm water across Meadowcreek Road. Downstream of Meadowcreek Road the stream enters the Grapevine Creek flood plain which is dense with trees and brush. The stream's confluence with Grapevine Creek is approximately 550 feet downstream of Meadowcreek Road. A 100-year flood would not inundate any residential structures along Stream G4. All roadways (Woodhurst Drive, Bethel School Road, and Meadowcreek Road) crossing the stream would be overtopped by the 100-year flood. The safety of each of these crossings was investigated and each was found to have a safety rating of less than six (Table V -1). Therefore, the improvements which are recommended address only the backyard flooding upstream of Meadowcreek Road. These improvements consist of removing the existing 8 x 6 foot box culvert under Meadowcreek Road and replacing it with two 10 x 6 foot box culverts at an estimated cost of $53,000. These improvements will remove Meadowcreek Road from the 100-year flood plain. They will also substantially reduce the 2-year flood plain, thereby reducing the likelihood of frequent flooding of the backyards in the area. The 2- and 100-year flood plains with this improvement are shown on Plate 3-4, Appendix F in red. In addition, guardrail and flood hazard warning signs are recommended for each of these crossings (see Section D.l. of this chapter). Construction of new fences obstructing the flood plain should be discouraged and problems with existing fences should be addressed on an individual basis. VI-16 6. Stream G5 Stream G5 is a tributary of Grapevine Creek which begins at Bethel School Road and flows southward a distance of 1550 feet to its confluence with Grapevine Creek. The source for this tributary consists of two ten foot inlets on opposite sides of Bethel School Road about 400 feet west of Moore Road. The lOO-year flood would cause both Carter Drive and Christi Lane to be overtopped resulting in minor flooding. (See Safety Ratings Table V-I). For the 2-year flood, however, existing structures are adequate. Complaints of erosion at Christi Lane were received. The exit velocities at Christi Lane are approximately 10 feet per second for the 2-year flood. The City of Dallas Drainage Design Manual recommends a maximum exit velocity of 8 feet per second in unlined channels. The estimated cost of grouted rick riprap and cleaning of brush and debriS immediately downstream of Christi Lane is $4,000 to correct this erosion. In addition, the road side ditch upstream of Carter Drive needs to be graded so as to direct the flow of water off of private property and alongside Moore Road into the existing culvert under Carter Drive. The estimated cost of these improvements is $3,000. The total cost of the recommended improvements on Stream G5 is $7,000. 7. Stream G6 Stream G6 flows in a southeasterly direction for approximately one mile from its point of origin at Shadowcrest Lane to its confluence with Grapevine Creek, upstream of Belt Line Road. Moore Road and Bethel School Road cross the stream. A storm sewer system enters the stream at Shadowcrest Lane. There are also several other storm sewer outfalls from adjacent developments between Shadowcrest Lane and Bethel School Road. The upstream reach of Stream G6 has a six foot wide concrete pilot channel with 4:1 grass side slopes. The pilot channel extends from the point of origin to Moore Road. Downstream of Moore Road the stream flows in an earthen channel of varying dimensions to Bethel School Road through the Northlake Woodlands East residential subdivision. Sparsely to moderately wooded areas exist within the channel and on the overbanks of the stream. The stream reach downstream of Bethel School Road is clean and straight for a distance of approximately 300 feet. The remaining 700 feet of the stream channel is within the Grapevine Creek flood plain and contains dense trees and brush. This stream had been previously studied by Kimley-Horn Associates (KHA, February 1990). Using cross sections surveyed by Ginn, Inc., Consulting Engineers, in August of 1988, Kimley-Horn performed hydrologic and hydraulic calculations, and investigated two alternatives; a grassed lined channel between Bethel School and Moore Roads, and a drop structure near Moore Road. No recommendations were made. Stream G6 flooding was studied using the existing KHA hydraulic model, updated and revised to better reflect developed conditions such as adjacent residential lot grading. Design flood discharges were also recomputed. The resulting lOO-year flood plain was delineated on the City's 200 scale topographic maps and reviewed to locate flooded structures and roadways. The residences at 602 and 606 Hawk Lane and 701 Bethel School Road were found to be inundated by the lOO-year flood. Moore Road and Bethel School Road are also overtopped. An analysis of the safety of these stream crossings was performed (Table V-I). Based on the street safety ratings alone, both Moore Road and Bethel School Road would not require any immediate improvements. In addition to the flooded houses on Hawk Lane, severe channel erosion problems exist just VI-17 upstream of Bethel School Road for approximately 350 feet. Erosion problems also exist in the stream reach immediately downstream of Moore Road. Additional complaints from Northlake Woodlands East homeowners included standing water, wet, marshy areas next to the channel, objectionable odors and mosquitos. The persistent wet, marshy areas are most likely sustained by lawn irrigation throughout this part of Coppell. In addition, standing water downstream of Bethel School Road in the Grapevine Creek flood plain is caused primarily by the lack of a defined outfall channel. One last complaint concerned over lot drainage in the area between Bethel School Road and Briarglen Drive just east of Moore Road. Drainage flows along the back of lots in this area to Stream G6. Some lots have been filled and runoff now flows over a retaining wall causing some erosion. a. Bethel School Road The recommended solution to solve the flooding of the residences upstream of Bethel School Road is to increase the capacity of the existing culvert by adding another 6 x 10 foot box culvert. The erosion problem immediately upstream of Bethel School Road can be rectified by constructing a 12-foot wide concrete pilot channel with four foot high retaining walls adjoining. The channel in this area has a existing vertical wall for approximately 50 feet on the Hawk Lane side of the stream. Dry rock riprap will be placed adjacent to the wall. This improved section will continue 300 feet upstream of Bethel School Road. The channel improvement will then transition back to an earthen channel cross section. Grading and clearing of the channel will continue for approximately 900 feet upstream of the transition to facilitate positive drainage. The recommendation downstream of Bethel School Road is to increase the stream channel to a 20-foot bottom width for 30 feet downstream. In addition, the channel should be graded to its confluence with Grapevine Creek to improve drainage of low flows and eliminate the standing water problem. The estimated probable cost for the recommended improvements (see Plate 3-3) along Stream G6 in the Bethel School Road area is $170,000. b. Downstream of Moore Road The stream reach downstream of Moore Road (approximately 600 feet) also has erosion problems. The recommended solution is to armor the existing channel with grouted rock riprap and place large rock riprap adjacent to the channel. The rock lined channel should carefully meander between existing trees to minimize the environmental impact. A typical cross section is shown in Figure VI-5. The probable estimated cost of improvements on Stream G6 downstream of Moore Road is $230,000. c. Detention upstream of Moore Road A proposed detention pond was tested on Stream G6 in the reach immediately upstream of Moore Road. The detention pond capacity is limited by the small amount of city-owned land in this area (less than one acre). Flood discharges were reduced by 10 percent at Moore Road but are not reduced at Bethel School Road. The Bethel School Road culvert would still be overtopped and erosion would be likely to continue in the reaches downstream of Moore Road to Bethel School Road. The estimated cost of the proposed detention basin is $160,000. This alternative is not recommended due to its limited effectiveness. VI-I8 It) M ..J It) W I - Z > Z W < a: ::z::: ~ (.) " - " u. C Z - . 0 t- o ,... en a: .- N - ... )( w (.) w a: CI) It) t- o N - 0 en u. :E It) 0 In . t- U. D.. N 0 In <" N > a:Z a: en 0 (.) D..- ~ - ~ _Z 0 - a: a:::::i () a: ..J CD CO W O..J ..J " < !J u.&W - - u. - t-Z 3: :E m u. a: ~Z en < (.) W 0 0< Z w .- !:i Z a:::z::: 0 a: Q. < "u - t- - en en en ~ u. Z W ,. :E It) - . 0 N ,... . . W ~~~.. . t- O 0 ,... Z co ~ o d. Marshy Areas Along Channel A low flow channel can be graded upstream of the Bethel School Road culvert and channel bank improvements made to help drain the wet, marshy areas. This channel grading is included in the Bethel School Road improvements (Alternative a.). A concrete lined pilot channel for this area was considered but rejected because of cost ($190,000), environmental impact (probable loss of many trees) and minimal effectiveness. Erosion and wet areas adjacent to the channel would likely continue to be a problem. The only positive benefit of a concrete low flow channel is to provide access for maintenance vehicles to areas along Stream G6. The most positive method of draining the wet, marshy areas would be a series of french drains outfalling to the earthen channel. A typical french drain installation is shown on Figure VI-6. This type of system is estimated to cost $2,500 per lot. This installation cost would be borne by the property owner. e. Over Lot Drainage Between Bethel School Road and Briarglen Drive - East of Moore Road. Runoff is cascading from the filled backyards between Bethel School Road and Briarglen Drive over and through a railroad tie retaining wall. A permanent concrete retaining wall and drainage should be installed. A 50 foot long 6 foot high wall could be constructed at a cost of $15,000 including a triple grate inlet and storm sewer pipe. Rock riprap should be placed on erosive areas where flows are concentrated and could also serve as an interim correction for erosion at the existing wall. 8. Elm Fork of the Trinity River The majority of the Elm Fork flood plain within the City of Coppell has been reclaimed. Remaining flood plain areas are in recreational use (Riverchase Golf Course). The Wellington Apartments and Sandy Lake Road are flooded by backwater flooding from the Elm Fork 100-year flood. They were flooded by as much as one to two feet during the May 1990 floods. A high water mark for this flood event was recorded near the apartments. The elevation of this high water mark was 446.1 and was based on a nearby benchmark set by another engineering consultant. A high water mark of 444.8 was recorded by the City of Carrollton on the east side of the Elm Fork. The U.S.G.s. preliminary estimate of the discharge at Sandy Lake Road on May 5, 1990 is 25,900 cfs. This would be slightly greater than the lO-year flood discharge as computed by the Corps of Engineers in the Trinity River Reconnaissance Study. A review of the Wellington Place Grading and Drainage plans (by McNamara Engineering Co. dated December 1985) indicate minimum first floor elevations for the apartments of 445.5 (Sheet C1). The apartments are apparently constructed lower than this plan elevation if the high water mark and estimated inundation depths are accurate. The plans also indicate 100 year (ultimate) water surface elevations of 446.3. The apartments and large portions of the site were apparently designed to be within the 100-year flood plain. The most recent Corps of Engineer 100-year flood elevation estimated in this area is approximately elevation 445. This elevation is approximately one feet lower than the high water mark shot in Coppell in 1990. Since there appears to be a datum discrepancy in this area it is recommended that all of these elevations and depths be confirmed by field surveys based on a known accurate benchmark. Other construction in the area includes the Riverchase Flood Plain Reclamation and the Comers of Coppell Shopping Center. The shopping center has a minimum first floor elevation of 448 based on plans. The apparent minimum fill elevation for Riverchase adjacent to the Wellington Apartments is 445 based on as built topography found in city files. VI-20 FILTER FABRIC ~ I N 6" PERFORATED PLASTIC PIPE TYPICAL FRENCH DRAIN DETAIL N.T.S. , , ~s"t~~ O~~W'-~ f~f:-~;J-Ji' ,,)i~ ~,,, \ \t \ \ GRADE LOW AREAS TO EARTH CHANNEL ON 1 % SLOPE (MINIMU IF POSSIBLE ~' 410 ;-~tltlE\.. ~ -STREAM G6 f:-ft.,t\1\'\ ~ ~\S1\~G ~ FIGURE VI-6 ~ TYPICAL BACKYARD FRENCH DRAIN INSTAllATION N.T.S. ,-. Due to the extensive existing reclamation, it is not recommended that the City of Coppell make improvements along the Elm Fork to eliminate the flooding of these apartments or any other developments in this area. The Fort Worth District, Corps of Engineers (FWD-COE) has flood control studies underway in the Upper Trinity River Basin. The Corps of Engineers has just completed a Upper Trinity River Basin Flood Control Reconnaissance Study. However, none of the alternatives proposed in the Reconnaissance Study is designed to completely eliminate the flooding of the apartments. The Indian Creek detention structure as proposed in the Reconnaissance Study will reduce the 100-year water surface elevation at Sandy Lake Road by approximately 0.80 feet to 444.4 msl. (1) This would give the apartments approximately one foot of freeboard if all elevations shown are correct. The parking lot would still be flooded by the 100- year flood. In light of this, the City of Coppell has requested the COE-FWD investigate this flooding in more detail in their ongoing Trinity River Feasibility Phase Study. The Corps of Engineers will also be preparing new aerial topography of the Elm Fork which should be used to solve the apparent datum discrepancy in this area. On site protection from Elm Fork flooding could be achieved by some combination of flood walls or berms, sluice gates and a pump station. These types of improvements should be constructed by the owners of the apartment complex. In the interim period, the owners and renters within the apartment complex should be advised to immediately purchase flood insurance to protect against loss. 9. Denton Creek Like the Elm Fork, much of the Denton Creek flood plain has been altered by channelization and reclamation. Immediately south of Deforest Road, along the downstream reach of Denton Creek the flood plain has been reclaimed along the west bank for the Lakes of CoppellNillages of Coppell residential development. The south flood plain and the channel are natural from Deforest Road to proposed MacArthur Boulevard. The flood plain on the north side all the way upstream to Denton Tap Road has been reclaimed by fill and levees for the Vista Ridge mixed use development. An overflow swale parallels and sometimes intersects the natural channel in this reach. This land was originally in the City of Lewisville but has since been annexed into the City of Coppell. The reclaimed land is currently undeveloped. Upstream of MacArthur Boulevard the flood plain on the south is currently being filled for the Lake Park Addition. West of this addition the majority of the flood plain land along the south bank of Denton Creek has been preserved as the Coppell Community Park site, extending to Denton Tap Road. This reach includes the confluence with Cottonwood Branch which drains a portion of western Coppell. From Denton Tap Road to SH 121 the flood plain and channel are primarily natural with only minor fill on the north bank for the Magnolia development. However, an approved fill permit exists immediately west of Andrew Brown Park which consists of reclamation of a portion of the Denton Creek and Cottonwood Branch flood plains. The Denton Creek hydraulic computer model utilized in this study was originally developed by the Corps of Engineers (C.O.E.) - Fort Worth District in 1978.<2> This model was revised by Kimley-Horn and Associates, Inc. for the 1990 Flood Insurance Study (PIS) update. The current hydraulic model has no cross sections south of Deforest Road, with the assumption that the downstream reach (approximately 18,000 feet) of Denton Creek is in the Elm Fork backwater. The Elm Fork 100-year flood elevation in this area is 447.23. The 100-year water surface elevation at the first cross section on Denton Creek (Section 18440) is 452.38. The original C.O.E. hydraulics model (1978) started on the Elm Fork assuming coincident peak flows and an additional cross section close to the confluence. Halff Associates adopted a similar approach and computed a water surface elevation of approximately 450. This is very close to the elevation computed for the 1978 PIS. Since the Kimley-Horn water surface elevation is higher and the PIS update has been approved, the higher elevation was adopted by the city. Due to this, there is a discontinuity between the Denton Creek and the Elm Fork water surface profiles (see Plate 5-12). This makes the regulatory water surface elevation along Denton Creek downstream of Deforest Road through the Lakes of Coppell development, questionable. This discrepancy may be solved during the C.O.E. Feasibility Study of the Upper Trinity River since a new VI-22 hydraulic model will be created for the Elm Fork and possibly Denton Creek. It is recommended that the City of Coppell request that Denton Creek up to Grapevine Lake be included in the Feasibility Study because of the extensive reclamation existing along this stream and to rectify the discrepancy in starting conditions. There are a few older homes along Deforest Road which are in the Denton Creek 100-year flood plain. Some of these residences may also be subject to backwater flooding from the Elm Fork. In addition, Deforest Road is also flooded. There have also been complaints of frequent flooding and erosion in Andrew Brown Park just west of Denton Tap Road. Alternatives to mitigate these flooding problems are discussed in the following sections. a. Deforest Road Flooding Several existing homes along Deforest Road lie within the 100-year flood plain. Some of the homes at the end of Deforest Road may also be affected by backwater flooding from the Elm Fork. Additional channel improvements to Denton Creek could possibly remove some homes from the flood plain. However, because of the environmental significance of this reach, the extensive existing reclamation and the likelihood that the area will redevelop, in the future, additional alterations to the Denton Creek channel are not recommended. Homeowners are advised to purchase flood insurance and investigate flood proofing measures to mitigate potential flood damage. -, There have also been complaints of erosion and frequent flooding of Deforest Road at the east end. This is primarily caused by the inadequate capacity of the ditch on the south side of the road. This ditch drains a large portion of the property north of Deforest Road. Ditch maintenance is addressed in Chapter VII, Section R, Roadway Ditch Maintenance. The existing ditch is a part of a partially filled but currently undeveloped tract of land in the Villages of Coppell subdivision. It is recommended that drainage design for this tract of land include pipe or open channel of sufficient capacity to accommodate runoff from the property north of Deforest Road. b. Andrew Brown Park Spillway Severe erosion of the Andrew Brown Park Spillway was reported by the City of Coppell Parks Department. This spillway is the overflow for a small lake within the park. A hike and bike trail exists along the top of the spillway. The concrete slope down into Denton Creek has completely eroded away and the flat area adjacent to the trail is being undermined. The recommended design solution to this problem is to install a new structural concrete spillway at a 1:1 slope down to the existing channel. A toe wall should be installed at the bottom of the slope with grouted rock riprap along the channel bottom to control erosion. The channel banks on each side of this structure should be cleared, graded and protected with additional grouted rock riprap. A guardrail should also be installed along the hike and bike trail at the top of the spillway. The estimated cost of this alternative is $35,000. It is important that final design of this spillway be performed in conjunction with design of the Cottonwood Branch berm (see Section 11.a.) and include a detailed hydrologic study of the Andrew Brown Park drainage area. Erosion all along this reach of Denton Creek within the park should also be addressed in the design phase. Complaints of frequent park flooding have also been received. These are addressed in the following section on Cottonwood Branch. 10. Stream D 1 Stream D1 is a tributary of Denton Creek which flows for approximately 1.4 miles from Thweat Road in a northeasterly direction to its confluence with Denton Creek. The lower 0.8 miles of Stream D1 were analyzed in this study. This analysis indicates that, under existing channel conditions, the 100-year -, VI-23 -, fully developed flood would inundate Coppell Road. Corporate Park Boulevard also appears to be flooded by the loo-year flood. a. Coppell Road Existing Coppell Road crosses Stream Dl at Stream Station 32+ 30 and is overtopped by the loo-year flood (fully developed watershed) by 1.1 feet. The recommended design solution to this problem involves the construction of an earthen channel for 280 feet downstream of Coppell Road and the installation of three 8 x 6 foot box culverts under Coppell Road. In addition the channel is to be extended upstream of Coppell Road along a new channel alignment through Station 42+00. This is necessary for efficient crossings at both Coppell Road and future Parkway Boulevard. The channel upstream of Coppell Road has been designed to convey flows to the new culvert location under Coppell Road. It has not been sized to convey the loo-year flood (see Corporate Park Boulevard discussion below). The estimated cost for these improvements is $118,000. b. Corporate Park Boulevard This street runs parallel to Stream Dl upstream of Coppell Road and is inundated by floodwaters which flow out of the Stream Dl basin to the north and towards Denton Creek. A detailed analysis of this complex area is beyond the scope of this study, however an approximate inundation line for the loo-year flood was determined and has been shown on the maps included in this report (see Plate 4-5). The most likely remedy to the flooding problems in the area upstream of Coppell Road is a combination of fill and channelization. The precise layout of these improvements will best be determined at the time of development in conjunction with both the property owners and the City of Coppell engineering staff. Therefore preliminary design is not included in this report. However, it should be noted that while encroachment is a possible solution to the flooding problems upstream of Coppell Road, care must be taken to insure the maintenance of flood storage volumes in the area. The reduction in valley storage for the stream should not exceed 15 percent of the total as a result of any design solution. Additional requirements for valley storage preservation are discussed in Basin Wide Alternatives, Section C.2. of this chapter. Due to the extremely flat topography in this area the final design solution to these problems will likely involve some form of detention ponds or lakes to compensate for the loss of storage due to encroachment and channelization. Detention can be incorporated into the development to reduce onsite drainage costs. 11. Cottonwood Branch Cottonwood Branch, a tributary of Denton Creek, flows in a northeast direction from the southwest comer of Coppell to its confluence northeast of Denton Tap Road. The stream bed is relatively flat in the upper and lower portions but steep in the middle area southwest from Coppell Road. The major road crossings are Denton Tap Road, Coppell Road, State Road (probable alignment for extension of Freeport Parkway), and the newly constructed Royal Lane. The channel in the Royal Lane area has been enlarged and straightened. The current city topographic maps reflect this channelization, even though the roadway had not been completed. The stream meanders downstream of the channelization to Coppell Road. Two new residential developments, the Shadow Woods and Oak Bend Additions, are currently under construction between Coppell Road and State Road. These subdivisions include fill along the flood plain fringe. . State Road, as it exists today, will be overtopped when the upper watershed reaches full development. However, the Flood Insurance Study indicates the top of road to be 0.5 feet above the existing upstream water surface elevation. Coppell Road is overtopped by 1.5 feet based on loo-year flood discharges VI-24 (fully developed watershed), but is only overtopped by 0.5 feet according to FEMA published water surface elevations upstream of the bridge. Downstream of Coppell Road the Villages at Cottonwood subdivision is on the left bank. The lots between Winding Hollow Lane and Cottonwood Branch have been filled approximately three to four feet above existing grade for the building sites. The back yards of these lots are within the tOO-year flood plain. The tOO-year flood elevation varies from 0.5 feet to zero feet below the top of fill and has caused concern for the homeowners along this stretch of the creek. The two year flood is only two feet lower than the tOO-year flood elevation. The Cottonwood Estates Development is on the east side of the creek, south of Coppell Road. These lots are well above the tOO-year flood plain of Cottonwood Branch. However, complaints have been registered by homeowners located near the ditch from the lake east of Cottonwood Road. This complaint is addressed in Chapter VII. Downstream from this area is an approved reclamation fill for the Parks of Coppell development. This includes the connection of Parkway Boulevard across Cottonwood Branch. In general the creek currently has minimal flooding problems. The Parks department has requested a solution to the frequent flooding of Andrew Brown Park between Denton Creek and Cottonwood Branch immediately west of Denton Tap Road. A Freeport Parkway bridge sizing and a discussion of the yard flooding along Winding Hollow Lane is also included. a. Andrew Brown Park Flooding Park ground elevations are 458 to 460. The 2-year flood elevation is 458 and the 10- year flood elevation is 461. The tOO-year flood elevation is 463.7, assuming Cottonwood Branch flows are able to cross the park to Denton Creek. If all flows were confined to Cottonwood Branch the tOO-year elevation would be 3.3 feet higher than the existing tOO-year water surface elevation. Proposed developments upstream would be flooded. Two alternatives are investigated to reduce the frequency of the park flooding. ---, i. Channelization and Bridge Improvements The first is to channelize Cottonwood Branch and widen the bridge opening under Denton Tap Road by adding another 25 foot span. This would enable the tOO-year discharge to pass . through the bridge and eliminate overflows to Denton Creek through the park. A berm (or fill) could be placed along the north side of the creek, thereby, preventing flow through the park. Flows from Denton Creek would then be the only flooding source for the park. A storm drain with a flap gate would have to be constructed through the berm for interior drainage of the park. The estimated probable cost of these improvements is $585,000. ii. Berm The second alternative would reduce the frequency of park flooding. The Denton Creek tOO-year water surface elevation upstream of Denton Tap Road varies from 46t to 463 and currently reduces the peak flows from Cottonwood Branch. A berm built to elevation 460 between Denton Tap Road and proposed Parkway Boulevard along Cottonwood Branch would reduce the frequency of park flooding to once in five years on the average. The berm would have to withstand overtopping flows. Any further reduction in the frequency of flooding to Andrew Brown Park, would involve a combination of berm and the bridge/channel improvements described above. A storm drain with a flap gate would also be required for interior drainage. The estimated probable cost of these improvements is $35,000 including interior drainage. Landscaping costs are not estimated. VI-25 The berm is the recommended alternative to reduce the frequency of flooding in Andrew Brown Park. Park uses are compatible with flood plain land. The alternative channelization of Cottonwood Branch with 100 year park protection is very expensive and would significantly reduce the existing valley storage (see Section C.2.) characteristics of the channel and flood plain. The small berm would protect the park from frequent flood events at a significantly lower estimated cost of $35,000. It is recommended that design of the Cottonwood Branch berm be combined with the spillway improvements design (9.b.) and overall design drainage within the Andrew Brown Park area. b. Flooded Road Crossings Coppell Road is overtopped by upstream flood flows. This flow does not constitute a hazard (see Table V-I) and improvements for flood control purposes are not immediately needed. State Road is currently a two lane road which crosses Cottonwood Branch at a low area. According to the topographic map, the building on the downstream south side of the stream may be within the lOO-year fully developed flood plain. The street is overtopped by 1.4 feet but does not constitute a high flooding hazard, see Table V-I. State Road is the proposed alignment of future Freeport Parkway. When Freeport Parkway is constructed, a new bridge with a low beam at or above elevation 494 should be included. The bridge opening should be a minimum waterway area of 1650 square feet to prevent erosive velocities. A bottom width of 75 feet with a bridge span 155 feet (2:1 side slopes) would be sufficient. This structure is estimated to cost $750,000 not including right-of-way acquisition. c. Winding Hollow Lane Residents along Winding Hollow Lane have registered several complaints of high water and backyard flooding from Cottonwood Branch. These lots were reclaimed for development with fill elevations set just 0.20 feet above the existing condition lOO-year water surface elevation (1984 PIS). Fully developed flows with existing channel and flood plain conditions, yield water surface elevations at or slightly above the top of fill. The 2-year (50 percent chance of occurrence in a given year) water surface elevations are approximately two feet lower. In several areas along this reach of Cottonwood Branch, the creek meanders close to the edge of fill and the flood plain is very flat with many low areas. The close proximity of the 2- and lOO-year flows to the backs of these homes is illustrated on Figure VI-7. The houses are set back from the street, near the top of the fill, however all building pads appear to be above the lOO-year flood elevation. Alternatives, such as channelization and construction of a swale on the east bank were considered to lower the water surface elevations in this area. Channelization would have significant environmental impacts on this scenic reach of the stream. The channel work would also have to be primarily on the Cottonwood Estates side which is also platted to the existing creek centerline. Therefore, channelization or alteration of the existing flood plain was eliminated from further consideration. Since there are no existing structures threatened by this flooding, it is recommended that stringent controls on upstream development be enforced by city staff. Two new developments, Shadow Woods and Oak Bend Additions, upstream of Coppell Road are already under construction. These residential developments include fill along the fully developed lOO-year flood plain fringe. No further flood plain reclamation should be allowed unless the valley storage preservation criteria, which will be discussed in Section C.2. of this chapter, is rigorously enforced. This criteria should help to insure that design flood elevations on Cottonwood Branch are not increased due to loss of upstream valley storage as the watershed becomes urbanized. VI-26 i\ i I .~\\ \ I '1'/\1.5 X FINISHED FLOOR ELEVATIONS FROM PLANS. ':"'~I Tl FIGURE VI- 7 WINDING HOLLOW LANE COTTONWOOD BRANCH N.T.S. 12. Stream C1 Stream C1 is a tributary of Cottonwood Branch which flows in a southeasterly direction for a distance of approximately 0.7 miles from a point upstream of State Road to its confluence. The lower 0.3 miles of Stream C1, from the confluence to a point approximately 300 feet upstream of State Road, was analyzed in this study. As a result of this analysis it was determined that the 1oo-year flood would overtop existing State Road by a depth of 2.0 feet. Field investigations also revealed severe erosion on the upstream face of State Road which was jeopardizing safe passage of vehicles over the road itself. This latter problem was reported to City of Coppell engineering staff and interim corrective measures were undertaken. Immediately downstream of the State Road crossing, the Oak Bend Addition is currently under construction. A portion of Stream C1 travels though the western comer of this subdivision. At the request of city staff this portion of Stream C1 in reference to the subdivision construction plans was evaluated. A discussion of this evaluation and the State Road culvert follows. a. State Road The recommended design solution for the State Road flooding is the replacement of the existing culvert with the installation of four 5 x 5 foot box culverts. The estimated cost of these improvements is $60,000. State Road will be the future alignment of Freeport Parkway as it extends towards SH 121. As part of the development of Oak Bend Subdivision the right-of-way for the east side of future Freeport Parkway has been dedicated and the developer is building half of the street bordering his property. This developer is installing two 8 x 6 foot box culverts sized for the ultimate 1oo-year flood discharge as per the Oak Bend Addition construction plans dated November, 1990. b. Oak Bend Subdivision At the request of city staff, Halff Associates also reviewed the proposed channel for Stream C1 within the Oak Bend Subdivision. The original plans proposed an open channel along the side and through the front yard of a residential lot. Access to the lot would require that a private driveway cross the creek. Many of the drainage complaints logged in this study concern areas where either drainage was designed . to run between the houses and has been blocked or creeks are privately platted with no maintenance entity other than the individual home owner. In this particular case the private home owner would have an urban drainageway carrying flows from the subdivision, as well as, areas west of State Road traveling through the front yard. In the interest of avoiding future citizen complaints, the following recommendations were proposed. i. Retaining Open Channel The lots containing the open channel should be separated from the subdivision. Rezone those lots west of Stream C1 as commercial or multi-family. The channel could then be routed along the edge and through the back of future apartments or light commercial fronting on State Road (Future Freeport Parkway). Development would take careful planning and the lots should be re-platted with a drainage easement maintenance clause. These lots could also be combined with adjacent property for commercial development. VI-29 li. Box Culvert - West A box culvert could be installed on the west side of State Road flowing south to Cottonwood Branch at the State Road crossing. This option would eliminate the existing Stream C1/State Road culvert which has been experiencing severe erosion problems. An easement may be required along the west side of existing State Road. lii. Box Culvert - East A box culvert could be installed on the east side of State Road flowing south along the back of the property, then east to Stream Cl. The developer has apparently selected the first option and will not build on this lot at this time. City staff should monitor this area carefully to ensure that future development adheres to the recommendations in this report. 13. Stream C2 Stream C2 is a tributary of Cottonwood Branch which flows in a northerly direction for a distance of approximately 0.4 miles from Ruby Road near State Road to its confluence with Cottonwood Branch. The lower 0.3 miles of Stream C2 were analyzed in this study. The analysis revealed no significant flooding problems along Stream C2, therefore no improvements are recommended. c. Basin-Wide Management Alternatives In the City of Coppell, the Elm Fork and its tributary flood plains encompass approximately 2000 acres of land. These streams provide the only scenic relief in an area typified by flat farm and grass lands. Currently, development pressures are increasing within Coppell. The City of Coppell is one of the two fastest growing DallaslFort Worth area communities. Between 1980 and 1990, the number of Coppell residents is estimated to have increased at a 15.8 percent annual growth rate. (3) In fact the recently published 1990 census data shows a population of 16,881 for the City of Coppell which is even larger than previous estimates. (4) While the watersheds still contain large undeveloped areas, increased land values make reclamation of relatively inexpensive flood plain land an attractive alternative for land developers. This study offers the City of Coppell a unique opportunity to manage the flood plain and reduce future flooding problems prior to development. Basin-wide management plans are developed to formulate a lasting, coordinated master plan for this future development in. and along the flood plain, as well as to control activities within the already developed portions of the flood plain. The ultimate goal of basin-wide management planning is to put flood plain land to its best and highest priority uses while minimizing city expense, preserving, and if possible, improving the ecology of the basin. The management alternatives presented were developed in light of information on topography, ecology, socioeconomic characteristics, flood plain delineation, and with regard to a review of existing easements and ownership of the flood plain. In many areas, access along the stream has already been significantly limited. In general, basin-wide alternatives such as hike and bike trails were not developed for these privately controlled areas. The basin-wide management alternatives considered are: . No Action . Valley Storage Preservation . Flood Plain Encroachment Limits Vi-30 . Storm Water Detention . Erosion/Sedimentation Control . Buffer Zones (Parallel Parkways) . Open Space Presexvation All of the alternatives considered are coordinated with the City of Coppell's Comprehensive Plan published in February 1987.'5) 1. No Action The first basin-wide management alternative considered is no action. A comprehensive basin-wide management plan would not be implemented. Landowners who wish to reclaim flood plain land will apply to the city fora fill permit on an individual site-by-site basis. The flood plain would continue to be defined based on fully developed land use discharges and reclamation projects would still have to meet all City of Coppell and Federal Emergency Management Agency criteria. However, downstream flooding could be increased due to valley storage depletion caused by fill in the flood plain. Development would continue on a piecemeal basis with no consistency or continuity. Public access to the streams would be limited or virtually eliminated in some areas. Environmentally sensitive reaches of many streams could be lost forever. The project cost of this alternative is zero. The long range cost is continued and possibly increasing flood damages within the city and the potential animosity of citizens toward their local government. 2. Valley Storage Presexvation As a part of the recently completed White Rock Creek Flood Plain Management Study, the effects of flood plain filling on the valley storage characteristics of natural streams were examined. Flood plain encroachment reduces the stream's natural ability to store floodwater often causing increases in downstream flooding. The main stem and its tributaries were tested for various levels of valley storage reduction. In general, loss of valley storage on the main channel caused increased flooding downstream. The smaller tributaries were less sensitive to valley storage reduction. The adverse effects of valley storage depletion have also been recognized in other watersheds. In 1985 the Corps of Engineers, sponsored by the North Central Texas Council of Governments (N CTCOG), began preparation of a Regional Environmental Impact Study of the Trinity River . and its tributaries in the Dallas-Fort Worth, Texas area. The April, 1988 Record of Decision establishes a zero percent reduction in valley storage capacity for the Elm Fork, West Fork and main channel of the Trinity River. For minor tributaries with drainage areas less than 10 square miles, a maximum of 15 percent reduction in storage will be allowed for the 100-year flood. Furthermore, the Corps now reviews the cumulative impact, upstream of, adjacent to, and downstream of reclamation projects.(6) Cumulative impacts are important because if one project is permitted, other projects should be considered to have the same chance of being built. Analysis of these results indicates that the effects of valley storage depletion are cumulative and can be responsible for greater increases in downstream flooding than any other urbanization change. In order to prevent increased downstream flooding, this parameter should be taken into consideration in the evaluation of all reclamation and channelization projects. Complete details of this analysis as well as descriptions of other relevant studies are found in the White Rock Creek Flood Plain Management Study.(1) Additional information on valley storage can also be found in this report, Chapter II, Section B.2.b. VI-31 As a result of these studies of valley storage sensitivity, the following criteria for valley storage reduction is proposed as a part of the Coppell City-Wule Storm Water Management Plan: Elm Fork, Denton Creek, Cottonwood Branch and Grapevine Creek No reduction in valley storage for the 1oo-year flood (fully developed watershed) All Other Tributaries 15 percent maximum reduction evaluated on a site-by-site basis for the 1oo-year flood Cottonwood Branch has a total drainage area of less than 10 square miles however, due to the existing and potential flooding problems discussed in Section B.11., it is included in the zero reduction category. It is also recommended that flood plain encroachment be strongly discouraged since encroachment increases downstream flooding and destroys a valuable natural resource. Existing cumulative valley storage data for the streams in Coppell is included in Appendix E, Summary of Hydraulic Data. 3. Flood Plain Encroachment Limits This alternative evaluates the establishment of flood plain encroachment limits for streams in Coppell. These limits would represent the maximum encroachment allowed for developers wishing to reclaim flood plain acreage. Extensive flood plain reclamation has already taken place along the Elm Fork, Grapevine Creek, and Denton Creek. Review of the existing property ownership, as well as coordination with the other flood plain management alternatives, indicates very limited opportunities for further encroachment. Therefore, this report recommends no further encroachment into the 100 year flood plain (fully developed watershed) for new residential developments. However, development pressures may require consideration of some flood plain reclamation in the light industrial and commercially zoned western areas of the city. This type of reclamation could be allowed as long as the valley storage and 'no rise' criteria discussed previously is met for all projects. These criteria are recommended to minimize increases in downstream flooding due to development. The upstream reaches of Cottonwood Branch, west of proposed Freeport Parkway are all zoned light industrial. . Portions of the creek near Royal Lane have already been channelized and some additional reclamation may be possible. The City of Coppell is already receiving complaints of high water from downstream homeowners along this stream. Although the finished floors of these homes are set approximately one foot above the 100 year flood elevation, the backyards have only 0.20 feet or less of freeboard. Upstream encroachment without compensating excavation could cause increases in flooding in this existing residential neighborhood in excess of that shown in this report. The same is true for Streams C1, C2, and D1, tributaries of Cottonwood Branch and Denton Creek, respectively. In general, no further flood plain encroachment is recommended, however reclamation on these tributaries could be allowed as long as the valley storage preservation criteria is met. Typical methods of preserving valley storage with channelization schemes are: 1) large channels with drop structures to maintain the existing water surface elevations, 2) swales paralleling the channel for storage compensation, and 3) detention ponds. Reclamation plans for any of these areas should include detailed hydrologic and hydraulic computations which clearly define the existing characteristics of the channel and flood plain and the proposed conditions including valley storage mitigation. Swales or detention structures should be placed in a drainage easement or right-of-way to ensure these areas remain dedicated to valley storage compensation. VI-32 4. Storm Water Detention Storm water detention is the deliberate attempt by man to retard runoff. A detention basin is a reservoir with a controlled outlet that is designed to release storm water during the flood at a slow rate, with the goal of reducing downstream flooding. Detention facilities store a portion of the flood waters up to an emergency overflow elevation and slowly release them to the stream through flood gates or by pumping after the storm has passed. Two detention concepts were evaluated for effectiveness in Coppell: regional detention and on-site detention. These types of detention were analyzed for reduction in the peak flood discharge for the lOO-year event. In addition to flood control, detention facilities are designed for groundwater recharge, sedimentation and erosion control, enhancement of water quality and recreational benefits. These beneficial uses were not considered in the development of detention as a storm water management alternative in this study. a. Regional Detention Regional detention basins for flood control are typically most effective in the upstream reaches of a watershed. Detention basins are generally sized to retain a specified volume of storm water, ranging from 10 to 25 percent of the peak runoff volume. Streams such as Grapevine Creek and Cottonwood Branch were investigated for possible regional detention basin sites in Coppell. In general, this investigation determined that it is not economically feasible to construct a regional detention basin of large size in Coppell primarily because of high land values and minimal effectiveness in flood damage reduction. Therefore, detention reservoirs sized to retain a specified percent of the peak runoff volume were not considered further. . Two individual detention basins were also sized and tested in Coppell. These basin sites were chosen mainly because of access and the availability of undeveloped land. A detention basin for Stream G 1 was investigated. but eliminated because of its high cost and minimum effectiveness in reducing downstream flood damages. A proposed site on Stream G6 would utilize city park land but was also rejected due to lack of effectiveness in reducing downstream flood peaks and velocities. b. On-Site Detention Cities like Austin, Texas, have both on-site and regional detention management programs. The general criterion for Austin's on-site detention is that the rate of outfall shall not exceed the peak flow of the 25-year storm prior to development. In addition, the ordinance requires that the capacity of the existing downstream systems be considered in determining the need for detaining more frequent storms. (8) An on-site detention scheme was evaluated on the upper portion of White Rock Creek and was found to be of minimal effectiveness in reducing the lOO-year flood discharge. This alternative was not explored for Coppell due to the high cost of installation (estimated to be up to $4,500 per installation), the unlikelihood of such a policy being applied to existing developments, maintenance concerns, difficulty of enforcing such an ordinance and minimal effectiveness in reducing flood damages. However, on-site detention could be effective for individual site flood control and one such basin is evaluated in Chapter VII, Section A Another location where on-site detention could be beneficial is the NCH tract on an unnamed tributary of Stream G 1. This type of detention should be tested on a site-by-site basis, based on compatibility with proposed development schemes and effectiveness in reducing downstream flood damages. VI-33 5. Erosion/Sedimentation Control The purpose of the storm water management alternatives investigated in this study is to mitigate the flooding of structures within the lOO-year flood plain and to develop alternatives to prevent future flooding problems while preserving the natural channel. The velocity of the water is held below erosive levels, wherever channel modification is necessary. Flow velocities are, and remain, erosive in many areas of the natural streams. The channel bottoms and banks will gradually erode, naturally forming a larger channel. Channel modification to curb erosion in natural reaches would be expensive and disruptive. Except for a few problem areas discussed below, the natural erosive processes should be allowed to continue. The stream will ultimately stabilize and rejuvenate the flora on and along its banks. Roads and structures should be built a safe distance from the stream to accommodate the anticipated enlargement of the stream channel due to erosion. a. No Action Erosion sites were identified in Chapter III. This alternative assumes that erosion control and/or maintenance will be handled by the property owner. Some of the erosion along the channels is natural and should be allowed to continue. Erosion and deposition sites should be monitored and corrected only as existing structures are threatened or increased flooding is caused. b. Grapevine Creek Downstream of Denton Tap Road/Meadowcreek Road Stabilization in the critical areas along this reach of Grapevine Creek is discussed in Section B.1.b in this chapter. Additional recommendations for streams in Coppell typified by meandering, narrow channels with steep banks are the establishment of a no flood plain fill or encroachment criteria and a minimum building set-back from the top of bank. This would prevent new construction along existing problem areas. These recommendations are also discussed in other sections of this chapter. c. Grapevine Creek Between Freeport Parkway and LBJ Freeway (See Chapter VI.B.1.) d. Stream G6 (See Chapter VI.B.?) e. Denton Creek (See Chapter VI.B.9.) f. Parkwood Channel (see Chapter VII.L.) g. Woodridge Channel (See Chapter VII. 0.) 6. Buffer Zones a. Parallel Parkways This alternative proposes a system of roadways paralleling the flood plains in Coppell. These parkways would provide access to the flood plain as well as create a buffer zone which clearly transitions between natural areas, subject to flooding and areas of other land uses. In this manner, the parkway prevents future encroachment into the flood plain. The flood plain within the buffer zone would either be placed in an easement or dedicated to the city. Figure VI-9, the Composite Open Space Plan, shows the proposed parkway system in relation to existing streets and the City of Coppell comprehensive thoroughfare plan. These parkways are designed as local or collector streets providing scenic routes as a part of the transportation network. In VI-34 general, they should provide secondary links through light commercial areas or terminate into a residential neighborhood. This will discourage 'cut-through' traffic from using the local parkway as a thoroughfare to the detriment of the neighborhood. A total of 2.3 miles of parkways are proposed, all along Denton Creek. Parkways along the other creeks in Coppell were not recommended due to existing development and/or commercial and light industrial zoning. Some cities participate in parkway construction cost to encourage implementation of the parkway concept and help offset the higher cost per lot caused by the single loading requirement for local parkways. However, the parkway cost estimate is for total construction costs, and does not attempt to identify cost sharing between the City and the developer. The costs also do not include right-of-way acquisition. The total estimated cost for the entire parkway system is $2,700,000. b. Parkway with Drainage Swale System A parkway and drainage swale system is developed as a flood plain reclamation alternative for tributaries. The parkway and drainage swale system demonstrates how the parallel parkway concept can be combined with a swale-like drainage channel to create an open space focal point for the adjoining developments. This alternative is a grassy swale-like channel centered between two parkways as shown on Figure VI-8. The swale provides flood conveyance and reclaims flood plain land for residential development, yet functions much as a local park. The merits of the swale/parkway system are seen when contrasted with the more typical drainage channel used in many existing developments. The typical drainage generally consists of a concrete pilot channel with grassed 4:1 side slopes. Residential lots usually back up to the floodway easement. The valley storage preservation criteria presented earlier in this chapter is difficult to meet with this type of channel and increases in downstream flooding can result. These increased flood elevations could have negative impacts on existing culverts and developments. Public access is also severely limited where private lots back up to the flood plain. Figure VI-8 and Table VI-I provide a comparison between these two types of drainage systems for a typical 92-acre residential subdivision. The advantages of the swale/parkway drainage alternative are: 1) environmental, and therefore property value, enhancement due to open space accessibility, 2) lessened probability of increased downstream flooding due to valley storage depletion, 3) additional right-of-way available for future unanticipated utility or drainage system expansion and, 4) enhanced storm water quality. Total development costs are approximately equal. The main disadvantage of the parkway/swale alternative is the reduced number of lots from the 92-acres (259 versus 274) and the higher development cost per lot ($9,310 versus $8,630). These higher costs could be offset somewhat should the city elect to participate in the parkway construction cost. TABLE VI-I PARKWAY/SWALE SYSTEM LAND DEVELOPMENT COST COMPARISONS Swale/Parkway Drainaf!e Conventional Drainaf!e Total Area 92.0 Acres 92.0 Acres Existing Flood Plain 25.0 Acres 25.0 Acres Reclaimed Flood Plain 18.1 Acres 20.3 Acres Developable 85.1 Acres 87.3 Acres Valley Storage Reduction 7.0 Percent 39.0 Percent . Developable Lots 259 274 Estimated Costs Paving $ 949,000 $ 936,000 Grading/Channel Excavation $ 325,000 $ 253,000 Storm Drainage $ 224,000 $ 270,000 Water $ 352,000 $ 342,000 Sanitary Sewer $ 246.000 $ 255.000 $ 2,096,000 $ 2,056,000 Engineering and Contingencies (20%) $ 419,000 $ 411,000 Total Estimated Project Cost $ 2,515,000 $ 2,467,000 Cost Per Lot $ 9,310 $ 8,630 · Does not meet recommendations for valley storage preservation. VI-35 Z o ~ I-' W OCl I- ~ III Cl !!! Z !:: ~ ZIIl ~ X ~ a: W 0 o W Ii 8: > ~ o ffi :J III < - ---.-~ ~r~-~-"-~ ...~ ll..1I. :E W :J:~ ~~ i0 ZW o~ -Z 0_ ><1: -0:: filo ~.... 0<1: ....z (5Q -~ o.Z >w ~> Z o o in N :::! W ~ ~ W ~ Z <I: 0:: o .... <I: Z o t= Z W > Z o o o N :I o W I- Iii W > ....I III W ~ W III ~ ~ ~ ~ ~ :I a: <C Z W a: o > c ~ W > ~ ffi ~ W J: ~ Cl~a: ~ c ~ Cl ~ W ~ ffi ~ ~~ J3-~~ ~= >< a: Z . W II. 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N o .... ~ :E W ~ :J:0 !::~ 3=w z~ Oz 0- -<I: >0:: CO ~~ 0~ ....~ <1:0:: o~ 0.- >w ~.... ~ en , -' -, /---------------------~ /"'- 'I ( 'I 1 a:.... ~z (/)w wl ex) ~O ..l t( ~ > z~ w a:w a: Wc ::) !:J Z ~ <cO u.. w US ~~ zc -[0 <c::) a:(/) c o o ~ 0) It) N o .... ~~ :s~ u~ Oll. l:I.l l:I.l~ t~ ..Je;j ;3~ =fI.l E-I::.l g:~ ~~ =Cl ~~ ... ..111 ... 7. Open Space Preservation Open space is essential to the quality of urban life and must be preserved within the land being developed for housing, shopping, and other uses. The benefits derived from preserving open space are numerous. The City of Coppell possesses areas of relatively undisturbed wooded land adjacent to the creeks and their tributaries, which provide habitats for wildlife. The preservation of these undeveloped areas is the critical factor in maintaining the high environmental quality of the region. The open space would enhance community pride, stimulate economic development resulting from increased property values, and provide room for passive and active recreational activities. Open space preservation would also improve the quality of life for future Coppell residents, as well as help control flooding by maintaining the existing natural storage characteristics of the flood plain. The City of Coppell currently owns or has prior claim to approximately 280 acres of the almost 2000 acres within the various flood plains. The remaining portion is privately-owned with limited or no public access. This report presents several general greenbelt and park alternatives which would increase public access and preserve this valuable natural resource. These greenbelt alternatives can be developed as individual projects or integrated with other flood plain management options. The alternatives which have been considered include Greenbelt Preservation/Open Space Acquisition and Hike and Bike Trail Systems. a. Greenbelt Preservation/Open Space Acquisition In this alternative, greenbelt acquisition by the City of Coppell is proposed for the areas shown on Figure VI-9. These proposed greenbelt additions are listed with approximate acreage in Table VI-2. It is assumed that this flood plain land would be dedicated to the City of Coppell by the adjacent property owners. I TABLE VI.2 I RECOMMENDED GREENBELT ADDITIONS STREAM DESCRIPTION APPROXIMATE TOTAL AREA (Acres) Grapevine Creek Flood plain area between Denton Tap and Bethel 15. Roads Stream Gl Addition to Hunterwood Park upstream of Bethel 13. School Road Stream G2 Flood plain area downstream of Bethel School Road 4. Stream G2A Flood plain area downstream of Bethel School Road 3. Denton Creek Flood plain area immediately downstream of 107. MacArthur Blvd. Denton Creek Addition to proposed Magnolia Park immediately 135. downstream of S.H. 121 Cottonwood Branch Addition to Andrew Brown Park on the north side of 9. the creek upstream of Parkway Blvd. Total Area Recommended Greenbelt Additions 286. VI-37 8f:- IA mu (6)"UonJSJnro"8 PU"81 ){l"8d s:nJSllqdW;} UTJlcI at1.Jsual{tJ.ldwo;) s,n;}ddOJ JO AlK) ;}q1 JO 1U;}W;}I;} UOHw.IY.)'M PU"8 S){l"8d;}lJ.L '{Y.lJY.Y.)U;}q II!A\ PU"81 ){l"8d l"8uonJPP"8 'MO.nJ 01 S;}nlI!luoo n;}ddOJ Sll 11lq1 Al;}Jffi SJ 1I "6-IA ;}lngH UO {Y.l!J!lU;}P! OSJ"8 ;}11l n;}ddOJ U! S;}HTIPllJ UOHW.IY.)l pUll S){llld glI!lS!X'3 PSOLl. XL 'oolsnoH 'SIZ :ll!ns '~1IJ.IdS J:l'lllH 01891 '.OllJ: '~I!M ::lOJnos (p:lnnm sSllnhrpnWJ:lH OOIAlollp oopolIAO 10ll!D pOll llpnWJ:lH mnm:lllqOS! 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";}.oll l;}d OO~'f:$ ;}q 01 {Y.l1llWJ1S;} S! SWIll l;}MOYPIIM pUll SSll.nJ ;}A!l"8U 1U"81d 01 lSoo;}lJ.L ';}ldOOd JO l;}qwnU l;}lW.nJ "8 Aq {Y.lM;}!^ ;}q Plnoo A;}ql os lI!llld pooy ;}q1 JO SW1ll PUlllSSll.nJ ;}q1lI! pUll sA-eM){llld {Y.lSOdOld ;}q1 gUOlll{Y.l1Ullld ;}q Plnoo Sl;}MOYPUM 'Al!Sl;}A!P 1Ullld ;}q1 glI!sw.olI! Aq 11ll!qllq ;}illPIIM ;}q1 ;}A01dWJ PlnoM PU"8 10100 gUJlds lUllffi!lq glI!p!^Old Aq 11;}qu~.nJ ;}q1 JO S:>H;}q1s;}"8 ;}ql ;}sw.olI! PlnoM 1l10Y ;}A!l"8U JO 1U;}wqsnqlllS;};}lJ.L "SW1"8 PUlllSSll.nJ lI! {Y.l1U"81d ;}q OSJll Plnoo Sl;}MOYPIIM PU"8 S;}SSll.nJ ;}AH"8N "glI!MOW ;}llnlr.u PJnOM q:>JqM W1"8 ;}ql oon{Y.l1 Aq;}1;}q1 pUll SUOnJpUOO IlllntllU Olll;}A;}l 01 {Y.lMOn-e ;}q Plnoo SW1ll{Y.lMOW ;}q1 PU"8 SPUlllS {Y.lpOOM ;}q1 U~Ml;}q SW1ll {Y.l1:Y.}I;}S "n-eJ AJlW PU"8 gUJlds ;}1"81 ;}q1 lI! An-enUU"8-!W;}S {Y.lMOW ;}q PlnoM PU"81do.o PU"8 S;}lnlSlld lI!"81d POOH "AJllS~U J! 'l;}uu-eq:> ;}q1 WOl} {Y.lAOW;}l ;}q PlnoM SJlq;}P pUll ~11 pwp pUll AJ"8S~U Sll {Y.lurud ;}q PlnoM ~1J. '{Y.lllnlr.u Sll{Y.lpnpuoo ;}q PlnoM 100lUoo l;}nn 'OOUllU;}llI!llW 1"8WJlI!W AJUO ;}A!~l PJnOM s;}AJ;}s;}ld 11;}qu~.nJ ;}S;}q1 JO SW1ll {Y.lPOOM --, I I L Park Master Plan shows several park site locations. The Storm Water Management Study identifies the flood plain bordering or within these park sites as especially scenic and environmentally significant. Since the majority of the undeveloped land in Coppell is flat farm and grass land, these park locations would provide the citizens of Coppell with adjoining passive and active recreation areas. The flat high ground would be used for active recreational activities such as soccer and baseball. The wooded flood plain would be preserved for passive recreational activities such as hiking, birdwatching, photography, nature study, and picnicking. Q In general, additional encroachment and/or channelization within the remaining flood plains of Coppell, shown on Figure VI-9, is also strongly discouraged. In those reaches where encroachment is allowed, proposed adjacent developments should be required to provide preservation plans delineating the specific scenic and environmentally significant areas. Some reclamation or channelization could be allowed if it can be proven that the existing natural habitats will not be harmed and all other criteria of the Storm Water Management Plan are met (see Section C.3.). r- I I U o o b. Hike and Bike Trails I' I I '- This management alternative proposes construction of a hike and bike trail system through the tributary flood plains. Figure VI-9 shows the locations of proposed hike and bike trails and their connections to other existing and planned trails in the City of Coppell. The master plan hike and bike trails shown are from the City of Coppell's Hike and Bike Plan (1985).(10) The complete trail system will provide a continuous route through Coppell with connections into a possible Elm Fork trail system. However, the trail system is not continuous along the stream channel itself. The trail diverts from the channel in several areas to avoid the 'privately maintained' flood plains. Hike and bike trails are proposed along one side of the channel except in especially scenic or environmentally significant reaches, where trails are proposed along both sides of the creek. r I ~l I ' , '--' The proposed hike and bike trails are generally ten foot wide concrete paths with ten to twelve foot wide pedestrian bridges at creek crossings. These proposed pedestrian bridges consist of durable, easy to install steel fabricated spans. Existing and future public roadways with city bike routes are utilized to connect the trails throughout the watershed. A total of 2.9 miles of additional hike and bike trails are proposed in and along the tributary flood plains. The total estimated cost of the proposed hike and bike system is $880,000. II I.- [! n Nature trails can also be included in the open space preservation areas discussed earlier in this chapter. These hiking routes could travel through especially scenic and environmentally significant reaches of the flood plain which should be maintained as natural. "Hiking only" trails would provide the residents of the City of Coppell with natural recreation areas for nature study, birdwatching and photography. The typical section is an 8 foot wide cleared gravel trails. Many wilderness or nature study trails consist of compacted native materials with the brush and overhanging branches cleared. D ! i L II ~ .J [I VI-39 'I L J ~r" --~~'. , ~ ---::::::-- , .. ~ 0 ::;; > :Ii JJ "0 0 :xl 0 .... )> 0 r..-" Vl c' :~ ~~',. _n z: ~" :~ . . .. r m ::;; Vi < r= r m ,/ ,. 0/ ~/b r ): ~ ~ -,- :Ii < z Cl MA ARTHUR BLVD. )t33f:iJ ~mn :0....0 l>S:z r="TlZ om Ul:on ~;>:.... Ul . -< ~:rio S:Z'" /-c -<.... , ~ C :0:0 <:~-- r-.- -- m :0 C) > :xl :xl o r c:; o z (') o s: "tI o (J) o =i Om 1J 1JO m "tI r m !z ;ri(J) x "tI >> CIJ(') m -0 r )> Z "'Tl Q c ::IJ m < ~\ m...."O roo s:<~ "T'l>_ Oral r r J:lmm "~n ....J:l0 J:ll>Z :::ZZ rnm Ul:!n ~l>= UlZO ~O~ s: * Z o -< f':' l>0'" "Oz5 "0-<0 i3~o xUl"O ~"'r l>6::: -tCz rn~Ul :! -0 Ul;::: Z CD-l-o -<:no o~~ -tr_ :rUlCD m-<r :OUlm en-lm mr S:S: ." o :0 ^ I . . . . . . I . . . . . . . . 1111111: CD m l>"O n"O X :!-;m 0:0 l>"O 0:0 -00 Ul -:ox 00 -t ;:::n 1l 0:0 "l>Ui -0-0 :0 -"0 mO Z -J:l 0 00 r;'r=-t :::0 rUl Cl -<m -"0 ~UlZ OUl :!m "0 :::0 rm -0 0 "."Cl zm "00 :!" OUl UlO l> -en Ul zm m:Ol> l>"O :0 ,,- m UlO "OOZ Cl :Ol> " m~ 0 ~S:O :0 ":0 Ul ~Cl 1l ~ m Ul;>: l> " Zn"O m 0'(' ":0 :0 m C:o Z mm " :::00 al m() al -o- m ;::: <o:01l m -t-t -tz " CDmO ~ ~ :Oal l> m UlZUl l>m ~ --tm 0 rr Ul -t ." .... :0 0 l> r () ." m r n C x m 1l -0 -t 0 -t Q :0 Zo C Ul O. ~ Z C -t m <: -<< ~ -< :0 Z l> m m Z -t 1ll> s: ~ Cl m ~:o =; r Ul 0 -t Ul ." -t." Ul s: :0 -t r -tr =; m :0 0 mO m m 0 00 Ul -t m 0 Ul -t -0 Ul "0 1l r l> r l> Z:If: Z'*' D. General Watershed Recommendations 1. Passive Flood Warning and Protection Systems An interim alternative to bridge replacement is the installation of a passive flood warning system with accompanying guardrail to alert and protect motorists concerning hazardous crossings. The Texas Supreme Court has ruled that cities and counties can be held liable for the failure to warn motorists of flood hazards (11). The recommended passive warning system consists of a warning sign such as "Beware of High Water" and a gage with easy to read depth markings. Guardrails should generally be included on the downstream side of the structure and in the overbank where velocities exceed three feet per second and the water depth over the top of the road exceeds one foot. It is recommended that the City of Coppell install passive warning systems and guardrail on all crossings receiving a "hazardous" or "unsafe" rating in Table V-I as an interim solution pending the implementation of the proposed design solutions for each of the high risk crossings. The nine high risk crossings located in the City of Coppell are listed in Table VI-4 along with the estimated cost of the proposed passive flood warning and protection systems. The total estimated cost for all nine crossings is $26,000. TABLE VI-4 PASSIVE WARNING & PROTECTION SYSTEMS STREAM ROADWAY CROSSING SAFElY RATING(l) ES71MATED COST Grapevine Creek Bethel Road Unsafe $4,000 Stream GI Bethel School Road Dangerous $3,000 CoppeD Road Dangerous $4,000 Bethel Road Unsafe $2,500 Stream G4 Meadowcreek Road Unsafe $2,500 Bethel School Road Unsafe $2,500 Woodhurst Drive Unsafe $2,500 Cottonwood Branch State Road Unsafe $3,000 Stream CI State Road Unsafe $2,000 TOTAL ESTIMATED COST $26,000 (1) See Table V-I for numerical safety ratings 2. Survey Monumentation System Monumentation can be an important component of an ongoing city-wide flood plain management program. Accurate and strategically located monuments can be used for consistent and unnorm update of plats and flood plain projects. The monumentation can provide the framework for engineering applications of a city-wide Geographic Information System. An example of such a system is the horizontal and vertical control network established in PIano. Permanent monuments were set at major intersections throughout the City on approximately a one square mile grid. Horizontal data for each station was established using Global Positioning Systems Methods. This is accomplished by occupying an existing National Geodetic Survey (N.G.S.) Triangulation Station with a Global Positioning Receiver and occupying the permanent monuments with a second receiver. Using a relative positioning technique, the difference in latitude and longitude of the previously unknown station is VI-42 [v-IA 'mnlIIJU1UI U lU 'lIJuId poog gql 1IJqlJM S){Uuq gql }O dOl gql PUOAgq 199} OZ pu-e Iguu-eq:> gm 1IJ gUOZ JgJJnq U !re pgAJgsgJd gq PInoqs UOnmg8gA IUJnluN UOnUAJgsgJd uonmg8gA ){ggJ;) '9 'pg-.l~W~U~W gq PJnOM puo~ du.1 U01Uga}0 m-egJ1SUMOp ){ggJ;) g1lJAgduJD uo uonmns gql !re q:>ns SWgNOJd luql gmsug PInoM mU~OJd uOJPOOS1IJ mI~gJ V 'Iguuuq:> m-egJ1S gql }O Alpudro 8~-poog gm pgs-egJ:)gp !req uonmns q:>rqM 1IJ s-egm AUMpOOg pgrrOJ1UOO Al!J AmUgp! 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Slu;:Jmnuom lL}O ){JoA\lgU S!q,L 'J;:Jl;:JmoJ:>!W lUId Igrr-eJud U mJM IgAgI :>numolnu uu pu-e spOJ JUAlIJ 81IJsn uonms q:>-eg UggA\lgq UnJ gJ;:JM S'(gA;:JI {-enUgJgma 'IOJ1UOO 'S'D'N 81IJsn pgqsnqmsg OS'(U !reM m-ep {-e:>!UgA 'sglUlIJPJOO;) gUUId glU1S gIqusn 011IJ pgJJg}SU"BJl Ugql 7. Flood Plain Dedication The flood plain land dedicated to the City under the subdivision regulations should encompass the greater of the following: . flood plain border . 20 feet beyond definable top of bank . 10 feet beyond a 4-to-l slope intersection with natural ground drawn from creek bottom or rock line 8. Zoning Map Flood Delineation Revision City zoning maps should be revised at the appropriate time to correspond to the fully developed watershed design flood delineation. 9. Park Preserves The City, through the Park Board, should establish official park "preserves" that are protected natural areas, not to be developed into active use parks. These areas would be owned by the City receive minimal maintenance and would provide connections to the existing and proposed greenbelt corridors. 10. Urban Storm Water Permits Nationwide studies have shown that urban storm water runoff contains significant pollutants. The Environmental Protection Agency will soon require the City of Coppell to permit these storm water discharges. The proposed regulations will require drainage system mapping, inventory, land use assessment, water quality sampling and development of storm water quality improvement programs. It is recommended that the City of Coppell take the following actions in preparation for the storm water permitting program. a. Drainage Data Base CoppeD should update its drainage maps and inventory. The information should be computerized as part of a Geographic Information System data base. A similar data base was created for the City of Richardson with over 5000 drainage facilities inventoried. Except for outfalls, this information is not required in the permit. However, drainage areas are required and storm sewer locations are necessary for determining those drainage areas. b. Base Maps The inventories required in the permit process will require base maps of the city at some usable scale (1" = 200' or 1" = 400'). New base maps, if obtained in modem digital format, could have many other uses, especially in the Geographic Information System (GIS) area. The maps could be rectified to larger area maps, such as the USGS 7.5 minute quadrangle map series, for regional consistency. Other GIS related activities that would be helpful include land use inventories. Identification and location of industrial land uses are emphasized in the proposed storm water permit rules. c. Sampling/Gaging/Flood Warning Systems Currently only two streamflow gaging stations are maintained on streams in this study. 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Erosion near LBJ Freeway $ 400,000 Stream G 1 1. Bethel School Road $ 555,000 2. Coppell Road $ 488,000 3. Erosion Downstream of Coppell Rd (Mitchell St) $ 22,000 4. Loch Lane $ 31,000 5. Unnamed Tributary-NCH Tract 2 6. Bethel Road $ 426,000 7. Freeport ParkwaylBethel Road Intersection $ 69,000 8. Undersized Storm Sewer U/S of Freeport Pkwy 2 Stream G2 Grouted riprap erosion protection $ 26,000 Stream G3 Meadowcreek Road Culvert and Drainage Improvements $ 29,000 Stream G4 Meadowcreek Road Culvert and Drainage Improvements $ 53,000 Stream G5 1. Christi Lane - Erosion Control $ 4,000 2. Carter Drive - Channel Grading $ 3,000 Stream G6 1. Bethel School Road culvert and channel $ 170,000 2. Moore Road erosion protection $ 230,000 3. Marshy Areas - French Drain System No cost to City 4. Tributary - Over Lot Drainage-Retaining wall $ 15,000 Elm Fork 1. Flood Insurance/Flood Proofing No cost to City 2. Request Inclusion in CO.E. Feasibility Phase Study No cost to City Denton Creek 1. Flood Insurance/Flood Proofing No cost to City 2. Andrew Brown Park Spillway $ 35,000 Stream D 1 1. Coppell Road culverts/channels $ 118,000 2. Corporate Park Boulevard 2 Cottonwood Branch 1. Andrew Brown Park berm $ 35,000 2. State Road (Future Freeport Boulevard) $ 750,000 3. Winding Hollow Lane 2 Stream Cl State Road culvert $ 60,000 TOTAL STREAM FLOODING SITES $ 5,564,000 1 Costs shown are total estimated costs. Possible city, developer or private participation not determined. 2 Development recommendation included in report. Cost not estimated. VI-48 6v-IA "^l~l~J~d~s J.1ms AlK) Ol IY.)P!^OJd E .S-IA ~lq~~ lI! 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'IVIDIN:;I~ aNY:;IOIM. NISVU 9-IA :fiUV.L VII. LOCAL DRAINAGE PROBLEMS ALTERNATIVES AND RECOMMENDATIONS In 1989, a subcommittee was formed to address drainage problems within the City. The Natural Drainage Subcommittee was one of eight subcommittees made up of volunteer citizens working together with city staff to identify public improvement needs within the City of Coppell. This committee toured sites where specific drainage complaints had been received. Table 1-2 is a list of these specific sites as compiled by that committee. The sites are shown on Figure I-I. Recommendations in this Chapter will address these problem areas and other drainage complaints compiled from City files that are not directly related to problems along stream channels discussed in the previous chapter. The City of Coppell continued to receive citizen complaints throughout the course of this study. A compilation of all these drainage complaints is included in Appendix C of this report. The majority of these problem areas stem from undersized storm sewer systems including, in some cases, lack of roadway ditch drainage capacity. Erosion sites on two streams not in the original scope of work, Parkwood Channel and Woodridge Channel, are also addressed in this chapter. The drainage problems are grouped into sixteen sites by area, as shown in Table VII-I. In addition, many of the similar complaints and miscellaneous problem areas are grouped together and presented at the end of the chapter. For example, some of the street flooding and standing water complaints are due to pavement subgrade failures and differential pavement settlement. In other areas, the problems stem from roadside ditches and drainage swales which are weed and/or silt choked. These types of problems are shown on Table VII-1 as Street Maintenance and Roadway Ditch Maintenance, respectively, and discussed at the end of the chapter. Miscellaneous problem areas which should be corrected by the individual property owners and other neighborhood drainage studies are also included. Twelve of the Local Drainage Sites have been addressed previously in a May 15, 1990 council workshop and preliminary report. (1) Information on those sites is also included in this chapter. The following chapters discuss problems and proposed solutions for the problem sites. Improvements proposed in this study are designed to current City of Coppell Drainage Standards. Those standards specify the use of the City of Dallas' Drainage Design ManualY} The manual recommends that all drainage systems (inlets and pipes combined with street and emergency overflow capacities) be designed for the 100-year flood discharge. Analyses of existing storm sewer systems were performed utilizing "as built" construction plans obtained from city files where available. Estimates of probable cost were calculated using City of Dallas Public Works Department currently stored unit prices as of April 2, 1990, where applicable. The total estimated costs include construction, engineering design, geotechnical testing, surveying, and easement documentation. Easement acquisition cost is not estimated. A. Freeport Parkway near Southwestern Boulevard 1. Statement of Problem Storm runoff from a large (78 acre) undeveloped area bounded by the St. Louis and Southwestern Railroad on the north, Freeport Parkway on the east, proposed Gateway Boulevard on the south, and Cotton Road on the west, flows along the railroad through an abandoned city water storage facility and over the curb into a storm drain inlet on Freeport Parkway (Figure VII-I). Most of this property, Gateway Business Park, is owned by Catellus Development Corporation (formerly Santa Fe Pacific Realty Corporation). In a letter dated September 26, 1990, Catellus expressed concern about inadequate storm sewer capacity in Freeport Parkway. VII-1 Z-IIA snootm[[~:)S!W s~wms J~tpO "i S~!S w~IQo.ld snootmJI~:)S!W -- guwoou p.rnh ptm l~.I1S ~:>tmU~~ q:>l!a h~Mplm~ -- . guwoou lOOJlS :.I~l~M guwums ~tmu~ltJ!UW l~.I1S -- guwoou l~.I1S ~tm'1 JU~I~ldUW d UO!SOJ3: I~UUlnIJ ~gp!JPOO M. 0 gu!J>OOU l~.I1S ~o~ ~ hptmS/Pm^~JnoH IDtp.IV:>UW N guwoou ~g~ ptm l~.I1S Uo!s!^!PQns SMOp~W W guwoou l~.I1S pm^~JnoH I~nurns guwoou 101 gUP{.rnd ptm OPUO;) SOPUO;) ~gP!JMO~W guwoou 101 gUP{.rnd Slu~wt.rndV ~){R'1 UMO.L gU!J>OOU l~.I1S ~o~ ~JOOW P.rn^~JnoH I~nurns~o~ ~JOOW '1 UO!SOJ3: I~utmq;) pooM)[.rnd )I guwoou l~.I1S lS~:>MO~qs/~^!Ja noU)l hptmS f guwoou pmA ptm l~.I1S ~^!JG tmMS ptm ~tm'1 )[M~ I guwoou ~noq ptm ~g~g 'pmh)[:mH ~tm'1 ~~a hp~S H ~^!JG sum gU!JOOs~ wo.g J~~M. WJolS ~o~ ~){R'l hptms l~ ~^!Ja sll!H gU!J~S~M. 0 gu!J>OOu l~.I1S ~~d J~wurns gUWOOg p.rn A s~ms3: pooMuOnO;) ~~Id J~WurnS/POOMUonO;) d guwoou p~OJ ~:>tmJ1u3: )[.rnd ~woH ~nqow ~lgtm!J.L u~PloD 3: guwoou pmh)[:mH (tpnos) l~.I1S ~h~ guwoou pmh)[:>~H (quoN) l~.I1S ~h~ guwoou pmh)[:>~H l~.I1S hqzO;) Sl~.I1S ~h~ ptm hqzO;) a ~g~u!WP JOOd :guwoou ~g~g ptm pmh '1~.I1s pooM.I~lunHl~tm'1 S)[OOJH ;) ~gro!wp JOOd :guwoou ~g~g ptm p.rn A Sl~.I1S n~MoH ptm )[:lO{JnH H guwoou l~J1S :~xm.r~^0 l~JUI .P^TH w~s~Mtpnos ~u . hM)[d uod~Jd V W3:'1HO~d 3:DV~a NOllVJO'1 3:.LI S S3HS SISX'1VNV 3DVNIVlIO '1V;)O'1 J-llA 3'1UV.L 2. Summary of Data Existing conditions are reflected on the 1985 city topographic maps. Drainage plans dated 1981 for Freeport Parkway were obtained. Proposed plans for Gateway Business Park were also reviewed. In addition, field reconnaissance of the problem area was made in April 1990, immediately following a storm event. 3. Analysis of Existing Condition Storm water runoff from this large relatively flat area flows generally north and east towards the railroad right-of-way. There are no defined drainage channels. Prior to entering the right-of-way, runoff is diverted by a berm which causes the flow to travel east along the right-of-way. At one point, approximately 1000 feet west of Freeport Parkway, the berm is broken and drainage from the railroad actually enters the adjoining property, thus aggravating the problem. At Freeport Parkway the flows concentrate, flow through the abandoned water storage facility site, and over the curb into the drainage system. The curb inlet is not sized to handle the runoff from this large area even in its undeveloped state. Because of the large drainage area and flat slope of the undeveloped tract, the excess storm water flow will persist long after rainfall has ended. This problem is temporary and should be solved with the development of the Catellus site. The inadequate storm sewer in Freeport Parkway is a more serious problem. The existing system picks up drainage from this 78 acre site at the southwest comer of the intersection of Freeport Parkway and the St. Louis and Southwestern Railroad (SL & SW RR). Storm water travels via a 6O-inch reinforced concrete pipe (RCP) south on Freeport Parkway to Southwestern Drive. Before entering Southwestern Drive and flowing east, the storm sewer pipe increases to a 66-inch RCP. Several curb inlets in Freeport Parkway are connected to the 66-inch RCP. About 1000 feet east of Freeport Parkway, the 66-inch storm sewer outfalls to an open channel which conveys storm water to Grapevine Creek. At Freeport Parkway, the 1981 drainage plans show a capacity of 174 cfs for the storm sewer system. Drainage calculations using current City of Coppell standards indicate a required capacity of about 530 cfs. This shows that the existing system is grossly undersized, most probably because it was designed for existing undeveloped land uses and a lower (5-year versus loo-year) design criteria than is currently used in the City of Coppell. In addition, the existing headwall is set at a high elevation to avoid other utility lines and the system will only flow half full before street flooding of Freeport Parkway occurs. Development of the adjoining 78 acre site will require some extraordinary drainage improvements because of the inadequate storm sewer in Freeport Parkway. 4. Proposed Solutions a. Interim The S1. Louis and Southwestern Railroad should be requested by letter to repair the berm and maintain the drainage ditches along the railroad. A 2- to 4-foot high berm should be constructed along Freeport Parkway and the flows redirected to the existing storm sewer headwall (Figure VII-I). These modifications should be performed by the railroad and the property owner. 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D r- SI..L()~I~. o~_S_OIJJ:HWESTERN RR. <=..._:.-:.::~::.~ --.-.....-.... .----- "Eo. 6 ~~~- =. ...~r EXISTING PAT~./ .----~..j OF CONCENTRATED FLOW INTERIM ~ DETENTION-'ALTERNATIVE 5176i~~~T:~gT EARTH AREA - 4-6 ACRES x REDIRECT RUNOFF Q OUT =200cfs. TO EXISTING CATELLUS DEv.eLOPMENT HEADWALL UNDER GROUND STORM SEWER ALT. INSTALL 508 L.F. 8'x6' BOX CULVERT / i 0: ALONG SOUTHWESTERN BLVD. OUTFALL! i I TO GRAPEVINE ,CREEK ALONG PROPOSED !, RAILROAD SPUR (SEE PLATE 3-f?) / V CAPACITY =465cfs. FUTURE GATEWAY BUSINESS PARK N -;- EXISTING PETROLEUM PIPELINE o 100 200 300 ~.........- . SCALE IN FEET . ~: .~ ) EXISTING STORM SEWER CAPACIT Y =200cfs. ON -. Iii ill! \ i III ) 0 , PRENTISSpRd;;){TIE.1 ~ FIGURE VII-1 SITE A FREEPORT PKWY. NEAR SOUTHWESTERN BLVD. 9-IIA "m~lSAS l~M~S WlOlS ~^pa UJ~l~Mqlnos ~lnJllJ ~ql UJ 1Y.)pnpUJ ~q OSIg Plnoo Wlg S!1Il lOj ~8gUJglP ~ql jO uo!Uod ~mos 'AI~lgu:r!lIfl "Al!18~lUJ PUg ~8gUJglP ~^Jl!sod lOj SU~^In:> AgM~^PP ~dSUJ Plnoqs JjglS Alp 'dn Uwp ~ql jO UOn~Idmoo uodfl "~q:>lJP ~8gUJglP ~PJSPgOl 8UflSPC~ ~qllno uwp Ol Ugld ~qlUJ 1Y.)pnpUJ ~q Plnoqs pOOqlOqq8J~U ~ql jO SlU~PJ~l ~llL "1Y.)pnpUJ SJ ImU~l lu~mdJnbg "~IgMS ~8gUJglP OM.} ~ql nglSUJ Ol JXlZffiln ~q PIn OM SOOlOj Alp 19q1 s~mnssg OSIg 1I "~~MS 1Y.)SOdOld ~ql jO 8UJq:>InmolpAq PUg 8UJpgJ8 PUg SlSOO UOn:>nJlSUOO l~I1I! 'pgO'M dg.L UOlU~a l~pun 8upoq ~pnpUJ lSOO SJllL "OOO'L€$ SJ SlU~m~^OldUIJ ~8gUJglP ~~ql jO lSOO 1Y.)lgUIJl~ ~llL "pgO'M dg.L UOlU~a jO lSW AI~lgJ1Y.)u:rmJ 1Y.)lrooI ~~l;) ~1I!^~dglD jO .{jglnqpl ngms ~ql OlUJ ~jlno OSIg Plnoo l~I1I! SJllL "1Y.)pU~urm~l OSIg SJ m~lsAS ~8gUJglP pgO'M dg.L UOlU~a 8UJlSPC~ ~ql OlUJ 8UJl~UUOO l~I1I! .x, lOOj ~ x ~ IgJ~ds V "1Y.)l:>nJlSUOO ~q Plnoqs AgM~8gUJglp-A~ng u~quw Ug Sl~llS n~MOH PUg ~:>onng U~M.}~g "pgOlTIgl ~ql 8UOIg PUg SlOI l~llS n~MOH ~PJS l~M ~ql jO lWl ~ql 8uo~ ~IgMS ~8gUJglP g jO UOn:>nJlSUOO ~ql jO lSJSUOOA~llL "Z-IIA ~ln8H uo UMOqS ~lg sm~Iqold ~8gUJglP l~llS n~MOH PUg l~llS ~:>onng ~ql lOj suonnlos 1Y.)pu~urm~l ~llL uonnIOS 1Y.)SOdOld "v "peOlTIgl ~ql lWU ~IgMS S!1Il jO pu~ quou ~qlle spuod OSIg l~leM. "~moq ~~ql jO lWl ~ql 8UOIg puod Ol l~lgM 8UJsnro Wlg IT!J ~:>gll S!1Il Aq 1Y.)~:>OIq SJ ~IgMS ~8gUJglP ~lJS Iooq:>s 8UJlSPC~ ~llL "~moq l~ns n~MOH ~ql jO l~M AI~lgJ1Y.)u:rmJ ~:>gll :>n~Iqlg ~ql jO UOJPnJlSUOO ~ql ~q Ol Slwddg m~Iqold ~8gUJglP S!1Il Ol lOl:>gj 8unnqpluoo l~qlOUY . "lU~lSPC~ -UOU AngnUJA OSIg SJ UOJSJAJpqns S!1Il jO lWl ~ql 19 peolTIg'M UJ~l~Mqlnos PUg SJnO"} "lS ~ql 8UOIg ~8gUJgla "S!lq~p PUg U!P Aq 1Y.)ggoP lUOOl~d O~ l~^O ~lg SU~^In:> AgM~^PP ~ql jO AUgm PUg 8UJPgl8~l jO ~U UJ ~lg n~MOH 8UOIg ~q:>lJP ~8gUJglP ~llL "AI~len~pe ~8eUJglp u~do ng UJglUJem Ol u~~el ~q lsnm ~lro ellX~ 'S!1Il sg q:>ns SWlg 19y AJ~^ UJ: "UoJSJAJpqns ~ql jO AlpOrem ~ql l~^O lUOOl~d ~"O Ugql s~I jO ~dOIS punoJ8 IeJnlgU qlJA\. 'j~n~l :>JqdeJ8odol ~Illn AJ~^ MOqS sdgm :>JqdgJ8odol n~ddO;) jO AlD ~ql jO M~JA~'M SUOJl!pUO;) 8UHSJX3 jO SJSAleuy "€ "~snoq ~ql OlUJ sd~s ~UIJl~mos l~lgM ~qllgql 1Y.)lms lU~PJ~l ~UO "8UJpooy l~llS pue pleA l~^O UJOOUOO 1Y.)s~ldx~ A~llL "1Y.)M~J^l~lUJ ~l~M SlU~PJ~l Igl~^~S PUg 0661 'L AgW uo ~pgm sgM OOUgSSJgUUOO~l PI~H "sdgm :>JqdgJ8odol ~861 SAD ~ql UO 1Y.)l~y~l SJ UOJSJAJpqns SJql 'l~^~MOH "1Y.)lrooI ~q lOU Plnoo OSIgl~llS n~MoH jO l~M ~ql Ol Iooq:>S AJelU~m~I3 uOl~d lOj SUgId "~Iqgng^g lOU ~l~M SUgld ~8gUJglP WlOlS PUg 8UJpgJ8 'uoJSJAJpqns SJql jO ~8g ~ql Ol ~na glga jO AJgurmns "Z "~Ju~dOJd ~ql jO luol} ~ql 8UOIg ~geUJglp u~do qlJA\. uOJSJAwqns l~Plo ue SJ SJllL "(Z-IIA ~ln8H) Sl~llS n~MoH PUg ~:>onng 8uOIg SlU~PJ~l mOl} 8UJPooy PlgA PUg l~ns jO SlUJgldmoo Igl~^~S 1Y.)^J~l sgq n~ddO;) jO AlD ~llL m~Iqold jO lu~m~lms "I Sl3a.llS 113MOH pUB '1;)()1I0U "U '~ ",' .: , " , . ", PROPOSED 5'x5' SPECIAL "V" INLET TOP 510.6 FL. 508.6 "... '- . ,PROPOSED 25' DRAINAGE SWALE ,,' -----" . ,~,:,:,,"l : . : l' ~ - ...:::::., . ~, ~':':::"':'::::::~::"'::'::~~PRAP .~ , . p. ',""""".' !(rc" I, ~~I::ING PONDING , ;. ~"~I D 'i 10 I '[9R ~UTFALL , 1611 E~ISTlNG ')1 :J) I . :~ ~I (I CJ .j 0 J,' I Q 0:,) ! ,.,f~!,,' i SCHOOL)' I . ;;-:=::: : ~ 0 II 0 LU 0 t ! 0.1 \ DRA'NAG1,( 1 ~ I 0 :. [J ~ ': ~I! . I II' " 0 1] -' ]. :'. · - ~ \V; '7' CJ I I 0 '~6UJJlL~=:~;,,~ODR~~j ~~..~ cs I J ~ j ALLEY; D'l 0 .~, '==~:3,--~ ~lIlTH~~Sl;,JtVP . I';L"-;,,~~lJ~, - , '! ~, '.IIo.D.IL CI. ,.=::::::;:-.~-,r-;- -.-.-. ... r ;" '. . . . , , - ~_.. '. --:::;,,:::=-::--- . '. I , 12')(. '.... ., . : -i ! ' N i : j RCBC \ l ~EAN AND G~'ADE' '. "'j . 'u · ROADSIDE SWAL~~~ijD I ~II~ D~IVEWAV C~LV R~, ; _.ID a: I ,I L r--' i \ 1 \.~.~ -, ( Q )L -'~:,-C.l ~ I ''-\'IW ./ '-"\) ~ fir' \,,/ ~ \/ , ~ :...I'~ ""', 'I~,I, ! II' , , / I I i \, .j, . PROPOSED DRAINAGE SWALE 512.8 X rn r\~ t~ iH:;~';(J{ir N FIGURE VII-2 SITE B BULLOCK ST. AND HOWELL ST. DRAINAGE IMPROVEMENTS o 100 200 300 ...,........- - . SCALE IN FEET S-IIA ~tp Oll~lnA\ lUl01S}0 UO!Sl~^!P ~ql snA\ ~l~IDlns UOnn(os 1II!l~lUI ~uO "m~(qOld ~UIpoOO ~utr'] S}(OOlg ~ql 01 SUO!ln(OS 1II!l~lUI (n1~^~S ~ln~n~^UI ~lnpossv mnH 'Jjms AlP }O l~n~l ~ql lV 1II!l~lUJ 'n SUOnn(os ~SOd01d '17 '~~n1n~ ~ql OlUI SA\OO l! '1~IU! ~ql ~^oqn qld~p SJql 01 Sl~~ l~llS ~ql UI ~UIPuod ~ql u~1fA\ '1~IU! ~ns ~ql }O dOl ~tp ~^oqn l~} 9S""O AfUO SI UOnn^~(~ 1000 ~qs!uy ~~n1n~ ~tp lnql l:Jn} ~ql SI ~U~P!~l ~utr'] S}(OOlg ~qlln m~(q01d ~ql 01 ~UIlnq!llUO;) "dmpnq oSfn fP.A\ ~Utr'] plnmG }O pu~ l~ ~tp In Sl~IU! ~tfJ.. '~utr'] S}(OOlg S"lP In ~ns ~ql UI puod Oll~lnA\ ~UIsnro SlU~^~ pooO 10UIW UI u~^~ ~utr'] S}(OOlg uo Sl~IU! ~UI1S!X~ ~ql olUI dn }(:Jnq fP.A\ ~d!d nn}lnO q:JUI-Z17 ~tfJ.. 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'~lUloJl~d oS(n snA\ ~U~P!~J ~ql}O A~AJns P(~g V '~P!^OJd 10U ~ln sqlnd A\OOJ~^O k>u~~b~m~ l~dOld pun AlJ~dOld ~ln^!ld uo Slu~m~~ UI ~lroO( ~Jn Sl~A\~S lUl01S '~uun(d A(Jood SI m~lsAs ~~nUInJp ~ql 'UO!l!ppn UJ '~un AJnpunoq ~~nUIn1p ~ql}O uonroO( ~ql U~A\l~q ~pund~l:JSIP SA\oqs oS(n dnm ~ln ~gnUIn1p ~tp ql!A\ sun(d gUIpnJ~ pun ~U!^nd ~ql }O uospndmoo V 'uo!ln11U~UOO}0 ~Ul!l 1~IU! ~lnu!W S"1 n glI!Z!TIln lUl01S k>u~n~lj l~A-S"Z ~ql 10} ~~!~P snA\ m~lsAS l~A\~S lUl01S ~tfJ.. '~A\~~1 ~1~A\ sun(d UO!l:JnJ1SUOO ~gnUIn1p pun gU!^nd ~gnmA II~ddO;) 'uO!lmU~mn:Jop :JNdnJ~Oloqd ~P!^Old snq ~H 'SlU~^~ lUl01S 10UIW u~^~ ~U!lnp ~~n1n~ SJq olUI dn ~U!}(:Jnq J~lnA\ ~u~!l~dx~ snq ~utr'] S}(OOJg S"lP In l~UA\OOmoq ~tfJ.. nlnG }O AJnmmns "Z '~~n1n~ ~ql UI l~lnA\ lUlOls pnq snq ~utr'] S}(OOlg S"lP In ~moq ~tp pun gUIPOOO l~llS ~U!ll~J gUI:JU~!l~dx~ ~Jn (f-IIA ~1~!d) UO!S!^!pqnS (~~nmA II~ddO;)) pOOA\J~lunH }O Sl~UA\OOmoq ~tfJ.. m~(qOJd }O lu~m~lms '1 UO!S!A!pqns pooM.lOllunHfaulrI S](oo.Ig '3 sanitary sewer system. This alternative would overwhelm the sanitary system, causing backups in houses. The practice is also in violation of TRA and State Health Department regulations. Another interim solution involves constructing berms around the threatened homes at 415 and 411 Brooks Lane. The berms would direct storm water around the homes to the south between 411 and 415 Brooks. The driveway for 415 Brooks would also need to be raised. Several problems exist with this solution. No easement exists in this area and fences obstruct the overflow path. Care must also be taken to ensure that the drainage problem is not transferred to the homes along Dillard Lane. Rainfall caught between the berms and the homes will be trapped and may increase the chance for foundation problems unless properly directed away from the houses. Last, but not least, the two homes in question, 411 and 415 Brooks Lane, have finished floor elevations between 1.5 and 2 foot above the top of curb and would remain subject to flooding. Another alternative explored involved underground detention. A detention vault storing almost 3500 cubic feet of storm water would probably be required. Inlet and outlet controls are necessary. This facility is estimated to cost $60,000 and annual maintenance costs will be high. This alternative will not improve the drainage for the rest of the system, which is substandard throughout the subdivision. The final interim solution involves flood proofing and flood insurance. The owners of the threatened homes could stockpile sand bags or construct low curbs to protect openings in the event of flooding. Flood insurance should also be purchased to protect against loss. b. Permanent The proposed improvements to the Hunterwood (Coppell Village) drainage problems have been separated into two stages to ultimately provide this neighborhood with loo-year flood protection. As can be seen from Figure VII-3, in Stage 1 runoff from the west will be picked up with two additional inlets and diverted south down the. property line between the Mary S. Myers property and Lots 13 and 14, Block B, Coppell Village Subdivision. The diversion will outfall into the existing creek with a proposed headwall. This should relieve the overloading of the storm sewer main at the sag inlets on Brooks Lane. Two additional 10 foot curb inlets will also be added on Brooks Lane, west of the existing inlets to provide additional inlet capacity. This diversion will bring the existing storm sewer main up to 25-year capacity. The estimated probable cost of this interim solution is $162,000, not including easement acquisition costs. Since there is no overflow path within this subdivision the entire underground system should be brought up to loo-year design. Stage II improvements consist of two 10 foot curb inlets and a diversion to the Stage I 42-inch storm sewer pipe on Dillard Lane. This will bring the entire storm sewer system up to loo-year capacity. The Stage II estimated probable cost is $63,000. c. Recommendations The recommended interim solution is flood proofing and flood insurance. The property owner at 415 Brooks Lane could install a 6 inch curb along the north and east side of the driveway and a low curb in front of the garage door. Flood insurance should also be purchased. For the long term solution the city should bring this storm sewer system up to capacity by implementing the Stage I and Stage II diversions. This would bring the entire system up to loo-year capacity and avoid future street and yard flooding problems. These recommended improvements are shown in red on Figure VII-3. VII-9 S.LN3W3^Ot:ldWI 3eVNIVt:lO OOOMt:l3.LNnH/3NV' S>lOOt:lB ,:) 3.LIS E-II^ 3l:1n~l:I 133~ NI 31V:>S -..........4"""'IIlI OOC oo~ oo~ 0 N , '(, ,I i /,./1 U': { i J ' " I 'i )1 r'l ') ;/ ~ I i 10 ~_.........". ,-"-...-., . ~~ ."...... ,( ,; /' ~ -< m :xJ (II Odo:>ot:l.8. r:r' / ~' ' ~ \ S~I)~ , ND, - CJ C1[5,~'v2JD DIG D [II :xJ ~ ,/ --,--.--" Ul _ 0. ,'N'l:,S)lOOt:l8 Ut ~ bJ tJ ITI~~OrPGJ CJ GU Cd C? L.,I ~. '-.. n!! ". CiJ[JCJ ~ J. L'9,IC) 3dOOO Y, o D. Cozby and Kaye Streets 1. . Cozby Circle - Lots 10 and 11 a. Statement of Problem The homeowners for Lots 10 and 11 on Cozby Circle of the Hunterwood (Coppell Village) Subdivision are experiencing ponded water in their back yards when it rains (Figure VII-4). b. Summary of Data The subdivision plans discussed in Section C for Coppell Village Subdivision were also used in the formulation of a solution to the Cozby Circle drainage problem. c. Analysis of Existing Conditions From field observations and conversations with the individual homeowners it was determined that the subject lots originally drained to the north across the empty lots adjacent to Cooper Lane. When the homes on these adjacent lots fronting on Cooper Lane were constructed the original drainage path was cut off and a ponding situation created. d. Proposed Solution The solution consists of installing a PVC area drain on each lot and routing an 8-inch PVC drain along the north property line across lots 8 and 9 to the closest curb inlet on Anderson Avenue. The estimated probable cost of this system is $17,000. 2. Kaye Street. a. Statement of Problem The homeowners along each side of Kaye Street are experiencing recurring flooding of outbuildings and ponding in their backyards (Figure VII-4). b. Summary of Data The drainage area map for Shadow Ridge Estates dated March, 1984 shows drainage from the back yards of the homes along the North side of Kaye Street flowing to Spanish Moss Court. The drainage area map for Coppell Village Subdivision dated December 21, 1980 shows drainage for the back yards of the homes along the South side of Kaye Street flowing to Cooper Lane. Several previous engineering studies have evaluated conditions on the north side of Kaye Street. The latest study by Kimley-Horn and Associates, Inc. proposes area drains with 4 inch PVC drain lines running between the houses on Spanish Moss Court and outfalling to the curb. This alternative is included in the discussions that follow. 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MOpRqS JOJ SURId UOJSJ^Jpqns ~lJ.L 'OOO'OC;$ Ol OOO'O€$ AI~lRmJXoJddR lSOO Ol ~lRWJl~ SRM uonnIos mp~lUJ UR lRql ~llr.>JPUI SUOnnIOs ~IQJssod pUR Slu~mmoo s,~nJWmOJ ~gRUJRJO ~ql JO M~J^~~ '~IQRHR^R ~J~M ~gRUJRJp }{JRd ~moq ~Hqom ~ql JOJ SURId uOp:>nJlSUOO ON RlRO JO AJRmmns 'Z 'l~J ~JRnbs OOC; AI~lRWJXoJddR JO ~JR UR gUJl~^OO 'pRO~ II~ddOJ mOlJ l~J OC; AI~lRWJXoJddR lUIOd R lR spuod J~lRA\. 'UIRJp lOU ~op (S-IIA ~J~H) '}{JRd ~moH ~HqoW ~~URP.L U~PIOD ~ql ol pROJ OOURJlU~ ~U m~IQOJd JO lu~m~lRlS '1 "I.l8d amoH anqoW al~8f.1l. oaplO{) ':.;{ 4. Proposed Solution a. Alternatives Considered i. Install drain pipe across Coppell Road to equalize flows in ditches. Total capacity of utilizing both ditches without overflowing onto the Mobile Home Park or the area across the street is 40 cIs., which is approximately the lO-year flood. ii. Regrade ditch along west side of Coppell Road. However, channelizing all flows to the north in the ditch will create additional flooding problems downstream. m. Install storm sewer pipe along Coppell Road with drop inlets along ditch. Design for ultimate discharge and connect street inlets to the pipe when the road is upgraded to four lanes. iv. Install storm sewer pipe in the mobile home park to convey flows through the park toward the west. Installing a 21 inch pipe to drain the local flows only, will not solve the problem since flows in excess of the combined ditch and inlet/pipe capacity will still pond in the sag. However, the sag area will drain faster. v. Regrade Park Lane to remove sag. This will reduce ponding, but due to bypassed flows from ditch, depth of flow down Park Lane may still be unsafe. b. Interim Solution Flows currently contributing to the ditch from the south should not be conveyed north at any increased rate, because it could cause additional flooding downstream (to the north). The ultimate solution will be provided when Coppell Road is upgraded to four lanes and storm drains installed. The best that can be done in the interim period is to install a 21 inch storm sewer pipe from the sag to Stream C2 at the west of the property and replace the existing inlet with a large triple grate inlet to handle the local flows. The ditch to the north can be cleaned out and the flow line lowered to the north about one foot from 'Park Lane to the 36 inch pipe under the next upstream private drive to reduce the frequency of overtopping at Park Lane. The engineer's estimate of probable cost is $90,000 for this project. This alternative is shown on Figure VII-5 in red. VII -15 'LJ1' L-----'''' I ~"7'C/ I, I / J)III \ ~ ~_____ //.dOI:f-.S~ --.-- J II _ ("~~ =-~ _____-*_______.OlJ. ____ _A~Otl JL "'-11-- ::-~-j _ 8'91t;)\ _____--' ~~~1(.,-~---- -~~-~I~- =r~2c:~7s~ 'f-=r--~?,~==-~- xrs-. ' ( r.!.. ! ./, I . ~ /; (..( I ~ ~ /~ ~'EJ=e~ :I \ L~. ~ \, ;:i ~ 0 ~1 g ". <. X' ;::: t,. om 3l: -m-- I '~- j /,J, > CJ II> E ( V~\ · f ( - I "~\ ''-Y \ I II ), _ "" I \ ~ ) I . I r \'-',,-. .' \ j J r ) , I'r ! 3dld Nlv~a' ','!': [:~-.-~~'''''~" b I gX .~ ' n~:l' j "G.. tOAd.9 'Ii .L=t1N1 .-i ' / 31::n.t) , 'F\t, i ~NI.LSt~3 },~~ ! d::>~ "~,(;-]]VJ.SN1~_____"/ o:":~l' x \O~h~ r:" I ~~. I / :~:f, 3~;~~ '~~~~~,~~~ici~eg: '11~n,:~~~sIlN~ ~ ' i \ ' ,.I nt, II. i.l I ( //' , i I .. "-"~~,,,,..j :1 \ / "\'j I ,,--'" HO.LIO 3~VNIVI:fO //-- "j II. r"~'83MO{ 9'Hol'd~"""~rhj"n .11 ~'. r'-- - . - ---~:----.t:=-J...n 0 - NW 3h" " \.. _m .. -'-- ~---- -- 4--,________,'/___ - -- --- - 0 n 9 .- I .( ,,~- --' "" v, "'-' , / \ I ,-, _--__ ,J ,,/ : "I/dOI:f 9&BQO ....,:-. I;, :' "j . (--' ',' .." \ I i \ I " " ,Ii ~~G?" .//)~}~\ - ~......, \ \ ' [I " -~AV":;~-~^7t\:j::'A_J,..j_.A'_"A_J'jk;"~~A~"""~'=;~"-<...~~';.'''-'--', \, ;, \ i. I ....2- ~ _ ---l-- ".N, 3AOBD )lvo.L, I \ If.'>...' \ \ ,...~......<.\ \. i I .. _. ,_d~_,"t~'-,y'yy-.y:::\?"'V~-::y-yr---~;C;y'''')ry''Y'-Y/~/-Y''''' '- y r:r...y'.. '.( '~.,., ,'~,,;..""'\ \. '.. 1,'11 i:ro t;J"pr1.CJ'i'o [J ~---D'-'----"") '-" ">"') \ \ \ 'II . U LU I, . ! ,\ X " SlN3W3^O~dWI 39VNIVI::IC }lI::IVd 3WOH 311BOW 319NVI1::I1 N3Cl09 3 31lS g-II^ 3~n~l.:I .L33:l NI 31V05 . 00& -~ ooc: oo~ 0 N ,-') .....' I - / / / \". i ( .....-.:-.. :,/ ( .; ! '", /.....7/ 1;:;Y ;1 /i'T,' II ~ ;/1 . .:.. ," .' )~-. ,;i,,-1 \ ! ( (i ! : 11- --r 2 \~, i. "'\ \. i .1..... 'i',' " ! '-~ F. Cottonwood Estates Summer Place Addition 1. Statement of Problem Runoff from Summer Place Addition and Cottonwood Estates on the east side of Cottonwood Road flows into a pond and then down a small ditch to culverts under Cottonwood Road (see Figure VII-6). The major street in Summer Place Addition, Leisure Lane, is frequently flooded and impassible. In addition the back yards of the residents along the flow path are frequently inundated by the drainage ditch flows. These residents along Cottonwood Road state that this yard flooding is not caused by Cottonwood Branch. 2. Summary of Data Drainage Plans from Summer Place Addition and Cottonwood Estates were obtained. Existing conditions, except for the pond area and Summer Place Addition, are reflected on the 1985 city topographic maps. In addition, field reconnaissance was performed in June 1990 and city files were reviewed. 3. Analysis of Existing Condition r-- Approximately 38 acres drain to the pond located between Summer Place Addition and Cottonwood Road. Half of this drainage is from Summer Place Addition and the other half from Cottonwood Estates. The runoff from Summer Place Addition collects into one storm drain under Leisure Lane and outfalls into the pond from the east. The storm drain from Summer Place is a 42 inch reinforced concrete pipe (RCP). The flow from the pond travels down a narrow ditch to the double 27 inch RCP pipe culverts under Cottonwood Lane. These culverts have a capacity of about 60 c.f.s. before the road is overtopped. The top of the road, according to city survey, is 480.1. The runoff to the pond during a 1oo-year storm event, shown on Summer Place Addition's drainage area map, is 112 cfs. The top of curb elevations on Leisure Lane range from 478 to 481.5. Therefore, whenever the capacity of the 27 inch culverts is exceeded Leisure Lane will be flooded at the low areas by over 2 feet. The back yards of the Cottonwood Estates residents will also be flooded when the capacity of the existing downstream ditch is exceeded. 4. Proposed Solution The capacity of the Cottonwood Lane culvert should to be increased. Correspondingly the capacity of the ditch from the pond to Cottonwood Road, as well as the capacity of the ditch from Cottonwood Road to Cottonwood Branch should be increased. The double 27 inch RCP culvert needs to be replaced by a 7 x 3 foot box culvert. The ditch should be widened to accommodate the full 12.5 foot wide drainage easement. The depth of the ditch should be at least 4 feet at a 0.5 percent slope. The estimated cost for removing the existing culverts, installing a 7 x 3 foot box culvert and excavating the ditch upstream of Cottonwood Road is $38,000. Recommended channelization downstream of Cottonwood Road will cost an additional $4,000 for a total estimated cost of $42,000. These improvements are shown in Figure VII-6. VII-17 .1.i~:I HI ~,Y:>S SJ.N3..3^OHd..1 3eVNIVHO 3:>>V1d H3....nS . OOOMNOJ.J.O:>> :I 3J.IS 9-1I^ 3yn91:1 ~ ~> '~i:..~ j",\ ' 1.,1 . 001: - .,., OOZ 001- 0 N " '............",~ \ \ ",- I , '. 4\ Ii. . ,) -', '-. ., '1<..} )l ) 't' ~, t; , 30Vld t:l3~WnS " "I \ )- , .... . , V~'; ~/ 1" - r 't/ '1--' I / ''''':' "CI::I COOMNO~ 0:> .. .:10 W"31::1J.S " 100 ~ =+= NOIJ."A" '-H:>J.IC C3S0 I::Id ) /; y ~I ;~~CjLQQ9 ~J.J.O:> '~0,.M(31::1 SNMOQ 10Q~=+= Nb 1VA":>X3 ) H:>J.1n msOdOl::ld ' .< -- (7.' 'z:. R~J l Iii J -{ t- OS H~IH 113ddOO '.n ", -<'::;. ,. .!, \ \ ~ '\ . .( ~. (' 3 \ , o~N~~~~i/\r 00 'r ,/ ./ / r~'.. ~. " /.; HON'v'tlB. dOOMNOIIOO tlO::J( ." NIVld G001~'tl'V3A-OO~ S310N3Gj" ) -/ / t ,~ .. "'<; J;J " ' '" .'d "''"C ~ /" G. Whispering Hills Drive at Sandy Lake Road 1. Statement of Problem Storm runoff is crossing Sandy Lake Road at Whispering Hills Drive and flooding yards on the north side of Sandy Lake Road (Figure VII-7). 2. Summary of Data The following documents are available and were reviewed relative to this flooding problem: City of Coppell 1985 topographic maps; Preliminary Engineering Study and Report for Drainage Problems along Fieldcrest Loop and Whispering Hills Drive in the Whispering Hill Subdivision in the City of Coppen Texas; City of Coppell Project Justification files and the Common Area Development Plans for Connell Skaggs Addition. In addition, field reconnaissance and field surveys along Sandy Lake Road and Whispering Hills Drive were also undertaken. A drainage area map was prepared based on this data. 3. Analysis of Existing Conditions Whispering Hills Drive and the Fieldcrest Loop development are the only recent developments upstream of this area. The culvert under Whispering Hills Drive at Sandy Lake Road was completed at the same time. Downstream from the site the Connell Skaggs Addition has increased the peak flows to the same drainage ditch. These increased flows are producing greater downstream water depths, thereby reducing the capacity of the Sandy Lake Road ditches. The overgrowth in the ditches also reduces the carrying capacity and increases the flood water elevations. In addition, overland flows are depositing sediment in the ditches further reducing the conveyance. The steepness of Whispering Hills Drive also creates high velocity flows. These flows, although very shallow, have sufficient momentum to push flows already overtopping Whispering Hills Drive across Sandy Lake Road. Sandy Lake Road is at its lowest elevation in the vicinity of Whispering Hills Drive. Therefore, any flows in excess of the capacity of the ditch will also cross Sandy Lake Road at Whispering Hills Drive. The capacity of the 32 inch diameter pipe under Whispering Hills Drive is 27 cfs assuming there is no downstream obstruction. This is less than the 2-year flood (48 cfs) discharging from the west. The capacity of the double 36 inch diameter pipes under Sandy Lake Road near the GTE site and Skaggs is 150 cfs., again assuming no obstructions downstream. Flows cross Sandy Lake Road in this vicinity from both the east and the west. This flow is equal to the 100-year predevelopment flows from the east but is less than the 2-year flood (177 cfs) from both the east and west. The capacity of the south ditch at Whispering Hills Drive is currently 33 cfs. This is about the same as the culvert under Whispering Hills Drive. The full flow capacity of the south ditch flowing from west to east, at the Sandy Lake Road culverts is approximately 80 cfs. This is equal to the lOO-year existing discharge from west of Whispering Hills Drive. However, storm water ponding to the elevation of Sandy Lake Road at the culvert crossing to the Skaggs Addition is already two feet higher than the intersection of Sandy Lake Road and Whispering Hills Drive. Therefore, the flows will not discharge from west to east during peak flows, but will actually discharge back toward Whispering Hills Drive from the east. The channel is in poor condition downstream of Sandy Lake Road adjacent to the Connell Skaggs Addition further reducing the capacity of the existing 36 inch pipes under Sandy Lake road from 150 cfs to 80 cfs. This is less than the 100-year storm flows. VII-19 OZ-IIA OL-IIA ~l~H UO }Y.)l 11! UA\oqs S! ~^n~W~lI~ S!U o}Y.)nmS1I! ~q U~^In:> xoq ~ l~ql }Y.)pu~mm~l S! II o}Y.)nmS1I! ~q Ol ~^~q ffi^\ (~U1Tl ~I~a Ap~qS '8 uon~s ~s) uOnJPPV s'ifflIDIS n~uuO;) ~ql1l! U~^In:> xoq }Y.)SOdOld lOOJ 8 x 01 ~qllO 'J{lOM. 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UO!SOl~ gU!snu:> S! pUU qlro ~ql l~AO u~lJo S! l~lUM S!ql SWlOlS gupna '~A!la noU)l hPUUS JO l~ hI~lU!~muq ~U81l~l:>MOpUqS 0lS' lU ~U~P!~l ~ql JO luolj lI! puu ~UUllU~ h~IIu ~ql lU spums hIlumsuoo l~lUM 'uomppu UI 'd~p qlro u~lJo '~P!S qlnos ~ql uo UO!l:Yo}Sl~lU! S!qlll! spums hIlumsuoo JjOUnll~lUM WlOlS '~Apa lSlnqpOOA\ puu ~Apa IIoU)l hPUUS JO UO!l:Yo}Sl~lll! ~qllu l~lUM gll!PUUlS puu gUWOOlJ l~llS JO ~IY AlP mOlj ~~or ~l~M Slll!UldmO:) m~Iqold JO lu~m~lulS 'I ~rJll;)3.QS aoU'] lSa.I3MopuqSfaAJ.!CI notfX APUUS 'f will be connected to the existing 'Y' inlet diverting the additional offsite flow back into the existing 27-inch RCP. These improvements are estimated to cost $60,000 including removal and replacement of the alley pavement. With the completion of Stage II the Sandy Knoll/Shadowcrest storm sewer system will have 25-year capacity with positive overflow in the street to Stream G6. The standing water problem at the intersection of Sandy Knoll Drive and Woodhurst Drive can be solved by removing and reconstructing 100 linear feet of pavement at the original design slope of 0.50 percent. The final design should include stabilization of the sub grade with lime or a similar subgrade treatment method. The estimated cost of this improvement is $19,000. The total estimated cost of all the recommended improvements in the Sandy Knoll Drive/Shadowcrest Lane area is $101,000. It is recommended that the pavement repairs at the intersection of Sandy Knoll and Woodhurst Drives and Shadowcrest - Stage I be performed concurrently for a total cost of $41,000. The Shadowcrest Lane area could then be monitored on a regular basis and Stage II scheduled as funds become available. K. Parkwood Channel Parkwood Channel is a .85 mile long tributary of Denton Creek which flows in a northerly direction from a point approximately 700 feet upstream of Moore Road to its confluence with Denton Creek, just downstream of a small lake (See Figure VII-H). The City of Coppell has received complaints regarding erosion problems in the reach of the channel downstream of Parkway Boulevard. The hydraulic analysis revealed potentially erosive velocities in this area (6-9 fps), especially in light ofthe sandy soils prevalent along the channel. The recommended design solution for this problem involves lining the existing side slopes for 2000 feet from the lake to the existing lined channel downstream of Parkway Boulevard. The slope would be lined from the existing concrete pilot channel up to an elevation one foot above the fully developed 100 year flood elevation. This solution would not only provide the desired erosion protection but would also greatly reduce the maintenance which the City is currently required to perform. The estimated probable cost for these improvements is $405,000. VII-27 S.LN3W3^OYdWI 30YNIYYO 3NV1 .LS3Y:lMOOVHS . .YO 110N>I AONVS r 3.LIS o ~ -II^ 3t:1n!)l:I J.:nNI .J... . ;t (\ . .~ (~)(.1 ~N3W3^"d A311" 3:>"1d3 d:>1::I IIL~ III SS"1:> .::1"1 0 ~ V 11"~SN S131NI 31Vll!) '17-;:~, I II I I I ... - -. _......_._-..~_ ___m "._u~_"_m ..... '"''. CJ - . () .. V ~[~ ~ r-,I \l::: J.aa:t HI a1Y:>S ,.., OOt oo~ Oo~ 0 N . . . - -.... . . . '-.. i \ , \ \ 'grJ()(' . --"'\ N o 100 200 300 ..........---- . SCALE IN FEET ~.. PARKWOOD 'J" .11t .. .; t,~ I .,., , . DUNt .~. :-> -;---- DUNCAtt DR-iv~ '... tJCJCJCJ'CJetJ - - - -......,...- - - E.E PL. / r--.. -... -~ I rC -- 'i l(Il[? ~ l~ ! \ .~-.-~- /' "~ ..."".----. ,,,..........- ~a.. )~ ...--- /..:..- .......... - FIGURE VII-11 SITE K PARKWOOD CHANNEL. 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',,- ~.< "~, ,.._...."~ u -1- _~~,' -~OQ~~K II '~' '..- \ . ji '\..... f ~. \ .+.....-...-.- --+- ... 11/.- ItI//, \// " j 1\ ~ o · i <'-Vt \ ....-+-.. ....~ I ! , , , , ~ r. )N<; T RtJ(. ~ leN ..._n,_, "'''''''''''' 1, ...__~__.....__ ' U ') ')~.> O. i--- fL . . l'"1 ~ - - . ._=-=-=-_..r-~.. .. 1'- .. C"). QQ \ t-~ CQ \ "-~. ~-' U) I ~ . 0 C C w :I ,.....---~/ i " , , \ t ,.......--., ! J / . \ I I . ' \\) I :~OPptLL I PARk J.. . . , ,.----- ~~,TS:"Vl .l. : // i \ /- / . '- ( . ! / - ....-. ,-.,' (') _j~Y"VY"-rv: ( I '", " (--'-.:> r ) COPPELL I.S.0. \ / aLeE ELEM. SCHO v -', 478.5 . x .' ........ //_. '-.../ . :::{/... \...,.j c" - (]) ----------.-=x--- o iO iO . Q ~ m~ ...z WW N ::>:1 ,.... :2W I ....> - ~O >...U)~ wwotfA. a:!:c! ~cnCCw CJ 0" - a:cc LL. wZ ~- OCC o~ :2Q 0 0 CO) 0 ... w 0 W N U. ~ 0 w 0 oJ ... < 0 (/) 0 N M. Meadows Subdivision 1. Statement of Problem The Meadows Subdivision (Figure VII-13) was designed between 1979 and 1989 in six phases. Flooding complaints have been recorded at several locations. Street flooding has been reported on Meadow Glen Circle, Meadowrun Drive and Leslie Lane on several occasions since 1985. 2. Summary of Data Subdivision plans for the Meadows Phases 1 through IV and VI were located. Grading plans for the storm sewer outfall down Parkway Blvd. through the Lakes of Coppell, were also obtained. Field reconnaissance of problem areas were made on April 26 and May 11, 1990. Field surveys were conducted on May 11, 1990. 3. Analysis of Existing Conditions The subdivision plans and field information were used to analyze drainage conditions. Much of the Meadows Subdivision, Phases I and II, drains to four inlets in Leslie as shown in Figure VII-13. The two inlets closest to Meadow Glen are at a low point. Water must pond to depth of 1.3 feet at these inlets before escaping the area down Meadow Glen. This situation is aggravated by poorly constructed valley gutters in the intersection of Meadowrun and Landsdowne Circle. This causes runoff which should continue east to inlets on Landsdowne Circle to flow south down Meadowrun ultimately ending up at the Leslie low point inlets. 4. Proposed Solutions Stage I of the recommended solution to alleviate the street flooding on Leslie involves adding an inlet on Leslie and adding storm sewer and inlets on Landsdowne as shown on Figure VII-13. These improvements have an estimated probable cost of $45,000. A temporary asphalt valley gutter could be constructed on Meadowrun south of Landsdowne Circle as an interim solution at an estimated cost of $1,500. This would partially alleviate the street flooding on Leslie. The storm sewer investigations revealed problems and discrepancies in other parts of the subdivision, most notably in the vicinity of Parkway Boulevard. Recommended solutions to these problems will require significant additional storm sewer construction. A proposed 45-acre drainage diversion at Woodmoor and Meadow Glen Drive to the east via Woodmoor Drive through Waterside Estates will relieve the Parkway Boulevard system. Inlets should be added in Parkway Boulevard, Meadow Glen Circle, Meadow Run Drive, and Marlee Circle. Drainage easements will be required in Waterside Estates. To date, no houses have been constructed in this subdivision, therefore construction of the diversion is recommended prior to issuance of building permits. Final sizes, alignments, and locations of all proposed drainage facilities should be established in the detailed design phase (not a part of this study). These Stage II improvements are estimated at $120,000 for the diversion and $30,000 for the additional inlets. VII-32 S.1N3W3AOl::ldWI 3~VNIVI::IO NOISIAIOSnS SMOOV3W W 3.1IS , ~ ~ -IIA 3I:tn~l:I \ ir.----t--''\.-11 W ,,~ \to ( \~/n .lS3t"'NI--j3;V:)S _,1"1 U ~ ' c-:l \90G 001 j 011 LJ / \ \ r--;~-:'~-71: (\ r// \ \ I Iii \ ...-' ) \ \"f'-_.___.-._.__'_-_'-.-/-~) ..........11.( I I I r'fY-''o--': II I , ! //'7 >< ~( ('" \-\1 / /~f :1 i c~~Cc4: ') '_'" _ \~~ J, ; i "'~ '" i \_-- '," "'. Ii U 0,9 "...---"'", \ '" "'-4. ". ~ \ """" " i ~ \ [) / .. [{ \..... ", \ I ,I \ ,: 101' ',\ ~\ n ~ VI' ~1~lJ. .- I ,...,\.. I '0 . [cY~ m ......, .. . '"" \ "'< \ '", ~/\ ",~ \ "-'1 ) ( \ ) . \ c) 3}f~' ~NI.1SIX3 OL l~:V:I.1nO l '\ ~\ :E\D / ( "\ i CD . 'd':n~.\rs ONIS AVM>U:l'.fd \ 'I ... '! 310i:1I0 331i:1YW NI .l:nNI,Q ~ - ~ i:l0 Nni:l'MOOY3W NI .l31NI,0 ~ - ~ N ~ MOOY3W NI .131NI,ot-~ '0 YM)li:lYd NI $.13111I1,0 ~-c: :OOY '~NIOOO .133i:1.1S 30n03i:1 0.1 II \39V.1S N. MacArthur Boulevard/Sandy Lake Road 1. Statement of Problem Storm runoff from Sandy Lake Road spills through the intersection of Sandy Lake Road and MacArthur Boulevard. 2. Summary of Data A field reconnaissance of the area was made on June 26, 1990. City topographic maps were also reviewed. 3. Analysis of Existing Conditions A 'Y' inlet is located at the northwest owner of the intersection. This inlet and the ditch draining to it are set at too high an elevation for runoff to enter the storm sewer system without flooding the intersection. 4. Proposed Solution The ultimate improvement of Sandy Lake Road will solve this problem. In the meantime, the 'Y' inlet should be removed and replaced with a storm sewer headwall. The existing ditch could then be graded for more capacity. This solution is estimated to cost $12,000. O. Woodridge Channel 1. Statement of Problem The Woodridge channel, (Figure VII-14) south of Sandy Lake Road from MacArthur Boulevard to Mapleleaf Lane is an earthen channel which requires extensive manpower and specialized equipment to maintain. The channel bottom and side slopes are eroding causing areas to hold water creating stagnant pools which provide habitat for mosquitos, snakes and rodents. 2. Summary of Data Review of drainage for the Woodridge channel did not reveal any flooding complaints. The major concern is erosion, slope failures, and the stagnant pools of standing water. Field reconnaissance immediately after severe storms in the Spring of 1990 also indicated no flooding problems. The sandy loam soil of this channel has a high erosion potential and two areas of slope failure were noted. Construction plans for this subdivision were requested from the City of Coppell and Lichliter Jameson and Associates, the engineer for the Woodridge developments. This subdivision is approximately 10 years old and only a portion of the storm sewer plans could be located. Channel improvement plans and MacArthur Boulevard plans were unavailable. In light of this, field survey work was performed to determine channel conditions at critical locations, such as MacArthur Boulevard and the first drop structure upstream of MacArthur Boulevard. VII-34 ~€-IIA .1'l-IIA ~l~H uo UM.oqs ~.rn suoJlnlos ~~1lL .000'6$ SJ uopnlos UIJl~lUJ SJql JO lSOO JY.)llml!l~ ~1lL .OO+1'€ l~U ~JnPnJlS dolp ~ql JO ~llSUM.Op pUR OO+o€ uopms l~U gUJlln:Y.>o UOJSOl~ ~Rq ~qt lR dRldJl JY.)lno~ JO lUlOJ ~qt UJ IOllUOO UOJSOl~ JO UOJlRIItnSUJ ~ql ~^IO^UJ PlnOM. uOJlnlos UIJl~lUJ UV .uopnIOS ~^JlRUl~lIR lSOO l~M.OI R ~q PlnOM. 'OOURu~lUJRm ~^JSU~lX~ ~lom gUJlJnb;}l pUR UO'SOl~ lSUJRgR gUJl:Y.)lOJd UJ ~^Jl:Y.)JJ~ S~I qgnoql 'I~UURq:> lond ~l~l:>UOO ~1lL .l~lRM. gUJpums mOlJ gUJWW~lS sm~Iqold SR n~M. 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These areas and their suggested solutions are: a. 281 Alex Street - Install area drain in front yard draining to existing channel in back. b. 604 Phoenix - Install area drain to street with erosion control along rear fence line. c. 232 Mockingbird - Channel maintenance and erosion control by school district. d. 201 Penuel - Install grouted rock riprap at base of retaining wall. e. 638 Parr - Install french drain in side yard. 2. Other Engineering Studies a. Bethel School/Pelican Drainage Study - This study was performed by Ginn, Inc. in 1989. It involved the design of multiple inlets on Pelican Lane and at the intersection of Bethel School Road and Falcon Lane. Construction of these improvements was completed in the fall of 1989. b. Oak Trail Drainage Study - This study was performed by DeShazo, Starek, & Tang, Inc. in January of 1990. The study addresses flooding of two residential lots located in the 100 block of Oak Trail. The proposed alternative solution involves the construction of additional storm sewer and inlets to alleviate the flooding problem. This project is currently under construction. c. Hill Drive Drainage Study - This study was also performed by DeShazo, Starek, & Tang, Inc. in 1989. The study addresses flooding in the 100 block of Hill Drive. The proposed solution involves the reconstruction of an alley behind the flooded residences at select locations and installation of additional inlets. This project has been designed and is currently awaiting funding. d. Fieldcrest Loop and Whispering Hills Drive Drainage Study - This study was performed by Ginn, Inc. in July, 1989. The study addresses flooding problems along Fieldcrest Loop and Whispering Hills Drive. Three alternatives to relieve the flooding problems along Fieldcrest Loop are proposed. These alternatives are: . Replace undersized driveway culverts and regrade the existing roadside ditchJswale to provide positive drainage; . Install underground drainage in the existing ditchJswale with associated inlets and grading; and , . Reconstruct Fieldcrest Loop with curb and gutter, inlets and a storm drainage. The first alternative is recommended by Ginn, Inc. at an estimated cost of $61,250. This subdivision was originally designed with open drainage along the street right-of-way in 10 foot drainage easements. Over the years the home builders and property owners have installed driveway and sidewalk culverts and landscaped their yards, virtually eliminating the capacity of the drainage swales. The recommended solution to this problem basically recreates the original grading design of the subdivision. This is the most logical and economical solution to the flooding problems. Since the homeowners also contributed to the problem it is recommended that a joint effort between the city and the property owners be investigated. VII-40 1 v-llA 'IlIA J:ndeq:> U! JY.)sodOJd S! ueld UOPtnU:)W:)ldUl! 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Utn:)p :)JOW U! JY.)ssn:>s!p S! uopdo P!llS!P lU:)W:)AOJdUl! :>nqnd:)lJ.L 'PP1S!P lU:)W:)AOJdUl! :>nqnd e qSnolq} JO .1uolJ-dn. JY.)P!^OJd :x[ p{noo SPUOJ ~lJ.L 'SlU:)W:)AOJdUl! :)ql jO uOP:>nJlSUoo :)ql ~U!PUOJ SJ:)Ui\\O AuOOOJd :)q} q}!i\\ uopeJlSJU!UIpe peJ1Uoo pue ~!S:)p gU!p!^OJd PW{ :)ql :)1[tn p{noo AlP :)lJ.L , ~ I TABLE Vll-2 LOCAL DRAINAGE PROBLEM SITES SUMMARY OF RECOMMENDATIONS I SITE I LOCATION I ESTIMATED COST! I A Freeport Parkway near Southwestern Boulevard $ 280,00Q2 B Bullock and Howell Streets $ 37,000 C Brooks LanelHunterwood - Stage I $ 162,000 - Stage II $ 63,000 D Cozby and Kaye Streets -- Cozby Street $ 17,000 -- Kaye Street (North) $ 102,000 -- Kaye Street (South) $ 111,000 E Golden Triangle Mobile Home Park $ 90,000 F Cottonwood/Summer Place $ 42,000 G Whispering Hills Drive at Sandy Lake Road $ 56,000 H Shady Dale Lane $ 39,000 I Swan Drive $ 30,000 Hawk Lane $ 26,000 J Sandy Knoll Drive/Shadowcrest Lane -- Sandy Knoll/Shadowcrest - Stage I $ 22,000 -- Sandy Knoll/Woodhurst Pavement $ 19,000 -- Sandy Knoll/Shadowcrest - Stage II $ 60,000 K Parkwood Channel $ 405,000 L Moore Road/Samuel Boulevard -- Samuel Soulevard/Meadowridge Condominium Flooding $ 69,000 -- Moore Road - Interim Pipe & Inlet $ 28,000 - Permanent Drainage Imp. $ 249,000 M Meadows Subdivision - Stage I $ 45,000 - Stage II $ 150,000 N MacArthur Boulevard/Sandy Lake Road $ 12,000 0 Woodridge Channel -- Interim Solution $ 9,000 -- Ultimate Solution $ 530,000 P Mapleleaf Lane - Stage I $ 49,000 - Stage II $ 28,000 --- Street Maintenance -- -- Roadway Ditch Maintenance -- -- Fieldcrest Loop $ 61,25W TOTAL LOCAL DRAINAGE PROBLEM SITES $ 2,791,250 r I i , , ....-.... Ii - o o o o r 1 ' d n IJ I' !~ ! ! ~ I ,- I I ' I",~ Ii I t " -' Ii I 1 Costs shown are total estimated costs. Potential city, developer or private participation not determine. 2 Recommendation not made. Less expensive alternative shown for comparison. 3 Recommended alternative and estimated cost from report by Ginn, Inc., July 14, 1989. o !-; k VII-42 VIII. IMPLEMENTATION OF RECOMMENDED PLAN In this chapter the flood plain and storm water management recommendations contained in Chapters VI and VII are evaluated and a suggested phasing plan for implementation is proposed. Available funding sources and additional funding options are discussed. The Federal government uses a tangible value analysis based on existing land use to evaluate flood control projects. This analysis consists of identifying costs and benefits with the objective of maximizing national economic development. Benefits are expressed as a ratio of costs. A ratio of 1.0 represents benefits equal to project costs and is the dividing point between an economically feasible and an infeasible project. Projects with benefit-cost ratios that are less than one are deemed economically not feasible. (1) This method of rating alternatives does not take into account intangible factors such as citizen complaints, environmental quality, ecological enhancement, neighborhood enhancement and aesthetics. Preservation of the flood plain to minimi7.e future flooding resulting from urban development of the watershed is also not taken into consideration. Previous Flood Plain Management studies have indicated that benefit-cost ratios on municipal flood plain management projects rarely exceed 1.0. In fact, the requirement of a benefit-cost ratio exceeding 1.0 would exclude consideration of most alternatives. (2) In light of this and because the flood plain management alternatives presented herein provide significant non- quantifiable benefits to both the residents of the City of Coppell and the environment, benefit-cost ratios were not calculated. Instead, the recommendations contained in this report are evaluated based on the following criteria: . Public safety . Property damage, . Danger to existing structures, and . Height, velocity and duration of flooding. The city council of the City of Coppell also created a subcommittee in August 1990, to study the City- Wule Storm Water Management Plan. The subcommittee consisted of two Coppell city councilmen, the Public Works Director and the Acting City Engineer, who were advised by representatives of Albert H. Halff Associates. The criteria listed above, as well as input from the subcommittee were utilized to develop the implementation plan discussed in Section B of this chapter. A Economic Feasibility The economic feasibility of a project depends largely on the ability and willingness of the citizens, acting through their municipal government, to pay for the project. The economic feasibility of a project may be judged by relating the cost, operation and maintenance estimates to the financial resources available for the project. An analysis of financial practicality evaluates whether the City of Coppell can afford this project. Storm Water Management projects are usually classified as a capital expenditure. Typically, they are paid for from general obligation tax bonds. The citizens of Coppell approved $13.5 million in a 1990 bond programY) Drainage improvements of $800,000 were included in this bond package, with $400,000 in bonds to be issued in 1990 and the remaining $400,000 in 1991. These are General Obligation Bonds with the Series 1990 bonds currently being issued by Bank One Dallas at a 7.22385% interest rate.(4) The city council has also approved $100,000 for repair of subgrade failures. Some of the projects included in this storm water management plan are caused by subgrade failures and could be funded at least in part with these approved funds. Storm Water Management projects are usually phased over several bond elections with interest rates varying with economic conditions. The phasing plan for the recommendations in Chapters VI and VII takes into account the already authorized drainage improvement bond funds, as well as previously targeted projects VIII -1 Z - IlIA =>.10J AlP Aq UO!l1l1ll1lSUJ ;)\q!SSOd P!.I1S!G \ooq:>S 1U;)PU;x!;)PUJ lI;X!dOJ q1lh\ :lU!.JllqS 1s<>;J ;)\q!SSOd .I!OO;)lI aIllJ!ll,d ;)pll.J:lqnS l:>;)fO.Id SJq1 01 OOO'OV$ At;)l11lllJXO.Iddll ~n!lffiUoo A\1u;).Illddll Sllq uO!S!^!Mns :l\I!lf!OfPll ;)q1 JO .1;x!OPA;lP;)l!.L OOO'09S $ 000'17 $ ~000'6 $ 000'9Z $ t<JQO'69 $ t<JQO'Lf $ OOO'S17 $ OOO'OZ $ OOO'S17 $ zOOO'61 $ OOO'ZZ $ 000'Z91 $ l000'ZOI $ 1 3:SVHd 'IVJ..OJ.. s:}gRD nRJU!R'M ~ ~gRD lJRlS s.qRd~'M uOJs0l3 mp~lUJ I~uuRq:::> ~gPPPOOA\ STIR1pnmD pUR sugJS ql!M SUI~lsAS gOJUlRA\ ~AJSSRd gOJPOOHWn~OpUa,J ~gpph\OP~WtPAIH I~nwRS SlU~W~A01dWJ q:>lJa UOJSJAJpqns n~MOH pUR :>J:>Onns: SURld UOJPnllSUOO A.IRUJWTI~ld qgnOlQl IR:>JUQ~lOOD ~ gUP~OJgU3 'A~Alns - I01lUa,J UOJS013 gUP~OJgU3 II ~gms - uOJSJAJPqns SMOp~W OOO'OSf$ ImOlqns I ~gms - uOJSJAJpqnS SMOp~W lU~W~ARd lSlnqpoOA\IIIoU)I APURS I ~gRlS - lS:}l:>MOpRqSIITOU)I ApURS I ~gms - ~UR'1 S){00ls: (qllON) l~llS ~AR)I ~ f Z 1 "OSOaOIA UOn~s o ~lJS 17-IA ~IqR.L '1 ~lJS s: ~lJS :>J~1:::> ~UJA~dR1D W ~lJS :SP3JOlJ /tJUO!1!PPV W ~lJS r ~lJS r ~lJS :::> ~lJS a ~lJS :Sp3JOlJ p3t10JddV A/snO!t13lJ Ol~A IR:>sy 1661-0661 ~ql10} ~In~q:>s ~q ARW ~fOld ~s:}lJ.L "UOnRlU~W~IdWJ I ~SRqd ~ql}O uRd SR ~pU~WW~l OSJR ~lR 'AI~lRJ~WWJ ~ldoPR ~q UR:> q:>JQM 's:}PJIOd ospuoq}O ~IRS lSlY ~ql }O lno 'uRd OJ l~I lR '~PUtlJ ~q Plnoo q:>JQM Sl~fOld Alpopd qgJQ IRUOmppR ~lR ~SRqd SJQl OJ p~pnpuJ OSJV oIPuna,J AlK) n~dda,J ~ql Aq gOJpUtlJ 10} IRA01ddR ~AnRlU~l ~AJ~l AP~lJR ~ARq q:>JQM Sl~fOld}o SlSJSUOO 1 ~SRqd uonRlU~W~IdWJ 1 ~SRqd 01 SlU~W~A01dWJ }O gUJSRqd os: O~pnpOJ lOU ~lR ARM-}O-Slqgp 10 SlU~W~~ SR ~lRls:} I~l }O SlSOO UomSJnooy oUonmu~wn:>op ARM-}O-lqgp 10 lU~W~~ pUR gOJls:}l 'gUJA~Alns 'UOJPnllSUOO 'gOJ1~~U~ ~pnpOJ pUR SlRIIOP 0661 uJ ~lR UMoqs s:}lR1UJls:} lSOO nv 0:::> uon:>~s OJ ~ssroSJP ~lR ~lnos gOJPUtlJ ~IqJssod l~qlO "SUIRiliOld puoq ~lnltlJ OJ ~~f~l ~lR SlU~W~A01d1U! l~qlltlJ ~SR:> OJ 'gUJUJRlsns-JI~S SJ l~fOld I01lUOO pOOIJ q:>R3 "SlU~W~A01d1UJ ~SOdOld ~ql }O s:}SRqd lu~n~sqns ~ql ~l~Idwoo Ol ~lJn~l ~q II!M gOJPUtlJ IRuomppy "SlU~W~A01dwJ ~gRUJR1P 10} n~dda,J }O su:nnp ~ql Aq ~A01ddR 000'008$ gOJlSPC~ ~ql Ol AI~lRWp'OlddR ~lRI~llOO Z pUR 1 s:}SRqd oS:}SRqd XJs OlOJ ~PJAJP SJ URld UOnRlU~W~Id1UJ ~ql IR1~U~g UJ o~SRqd lRql }O uonmU~W~Id1UJ ~qllO} suonRpU~WW~l }O uOJssroSJP IR1~U~g R SUJmuoo ~SRqd q:>~ pUR URld gOJSRqd ~ql OJ ~lR:>JPOJ ~lR Sl~fOld ~s:}lJ.L os~mlU~ l~qlO 10 Sl~dOI~A~P 'Sl~UMO Au~dOld IRnpJAJpOJ ql!M SUOlJ~ lOJof qgnOlql ~pUtlJ ~q OSJR Plnoo UOd~l SJQl OJ ~SOd01d Sl~f01d I01lUOO pOOIJ ~ql }O IR1~~S on~dda,J}O AlK) ~ql }O Ipunoo AlP ~ql Aq Other Phase 1 Recommendations Grapevine Creek - Erosion near LBJ Freeway - City staff should initiate a coordination meeting with the adjacent developers/property owners to encourage a cooperative construction program for the proposed drop structure. Elm Fork and Denton Creek - Send request to Fort Worth District Corps of Engineers regarding detailed study of the Elm Fork and Denton Creek in the Feasibility Phase of the Upper Trinity River Basin Study. Adopt the valley storage preservation and other recommended ordinance revisions by amendment to the existing Flood Plain Ordinance. Adopt a construction site erosion control ordinance. Initiate a roadway ditch improvement program with city forces. Initiate a street maintenance program for repair of subgrade failures. Initiate a creek inspection program. Enforce finished floor certification by a Registered Public Surveyor for all new construction adjacent to the flood plain. Probably the most important flood control recommendation in the Coppell City-WuJe Storm Water Management Plan is also included under Phase 1 Implementation. This recommendation is that the existing valley storage characteristics of the channels and flood plains within Coppell should be preserved. Valley storage is the term Used to describe a stream's natural capacity to store some portion of the runoff volume as a flood wave moves downstream. Previous studies have shown that flood plain encroachment and/or channel modifications typically reduce the valley storage of the stream, generally increasing downstream flooding. It is also recommended that all designs along the creeks of Coppell be based upon loo-year flood elevations for a fully developed watershed. The minimum finished floor for all new construction should be 2 feet above this loo-year flood elevation. The adoption by ordinance of this criteria as well as the other recommendations listed above are very important parts of the Phase 1 Implementation Plan. The Phase 1 Implementation plan totals approximately $560,000. Several of these projects could be funded in part by other entities as indicated in the table. It is recommended that design for all of these improvements be initiated immediately. It should also be noted that the Meadows-Stage II diversion design and easement documentation is recommended during the Phase I implementation. This diversion is required to reduce street flooding on Parkway Boulevard. There is already evidence along Parkway Boulevard of storm runoff flowing over the top of curb and this condition will worsen as the area continues to develop. The diversion is proposed through Waterside Estates to an existing lake. Thus far, the lots within this subdivision have not been developed. An easement for the outfall should be obtained before the lots are sold and homes are constructed. VIII -3 '\7- IlIA OAI~^!l:Y.)d~l 'spUtlJ UO!lwJ:Y.)~ pUl~ IDI1Rd pUR l!Rd~l l~llS l~pUn ~pUtlJ ~q Plnoqs ARMmdS ){lRd UM01g M~lPUV ~ql pUR ~JnTIRJ ~pR1~qns lSlnqpOOMlllOU)l APURS ~ql 'SR q::mS 'Sl:l~f01d l~QlO O~nU~^Y UOSl~PUV uo l~lU! l~M~S WlOlS ~UJlSPC~ ~ql OlU! 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E-zOSZ'19 $ dO<Y]lS~l:lPI~H Z.S UO!l:Y.)S OOO'Of: $ ~^PO URMS I ~l!S ~UJPOOH lu~wllRdy ){~lJ UMOl. pUR zOOO'gz $ Au~d01d U!lsny - pRO~ ~lOOW '1 ~l!S zOOO'L 1 $ ~Pl!J AqZOJ o ~l!S zOOO'111 $ (qlnos) l~llS ~A-e)l o ~l!S l000'Sf: $ ARMmdS ){lRd UMOlg M~lPUV ){~lJ UOlU~O 010 ){~l:lMOpWW JO WW1lSUMOO qpl. 000'f:8 $ ){~lJ ~U!^~dR10 ~WRUUfl-UO!S013 ){~lJ ~U!^~dR10 010 ){~l:lMOpWW lR qpl. OOO'L $ ){~lJ ~U!^~dR10 ~WRUUfl-UO!S013 ){~lJ ~U!^~dR10 000'1f: $ SlU~W~^OldWI l~uuRqJ ~UR'1 q:l<Y] 10 WW1lS Sll~^lnJ pUR (:~A\. '"IN) OOO'OL 1 $ ~I~uuRqJ ~pRO~ Iooq:lS I~Ql~g 90 wW1lS .Z661-16611R~A lrosy ~ql10J spuoq JO ~IRS pUQ:Y.)s ~ql Aq llRd UJ lSWIlR '~pUtlJ ~q ARW q:l!QM Sl:Y.)fOld JO SlsySUOO Z ~SRqd UO!lRlU~W~IdWI Z ~SRqd oz 3. Phase 3 Implementation Phase 3 consists of projects which have a high priority but may require additional public or private funding. Grapevine Creek Erosion - Denton Tap Road to Moore Road Stream G3 Meadowcreek Road Improvements Stream G4 Meadowcreek Road Improvements Site P Mapleleaf Lane - Stage I Stream G6 (NL WE) Moore Rd. Erosion Protection Stream G5 Erosion Protection & Grading (Carter Rd. & Christi Ln.) Stream G2 Erosion Protection behind Plantation Dr. residences Site F Cottonwood Estates/Summer Place Addition $1,350,0001 $ 29,000 $ 53,000 $ 49,000 $ 230,000 $ 7,000 $ 26,0001 $ 42,000 Stream G 1 Freeport ParkwaylBethel Road $ 69,0001 Intersection (Coppell Commerce Center) Cottonwood Branch Andrew Brown Park Berm Site E Golden Triangle Mobile Home Park TOTAL PHASE 3 $ 35,OOOZ $ 90,0001 $1,980,000 2 Possible cost sharing with property owners, developers and builders. Parks and recreation funding. VIII -5 9-IIIA '~Jnp'll} lO} {Y.)lOHuom ~q Plnoqs IIllM ~1J!UJlll~l ~n PllOllllll ~UJ1SJX'3 '101 l~d OOSZ$ lSOO 01 {Y.)lllmn~ l~UM.O hu~dold ~ql hq {Y.)IIlllSUJ m~lShS UJlllP q:)u~ld '~mn Sfijl III sm~lqOld UO!SOl~ ~l~A~S hUll MOqS 10U P!P uOp:Y.)dSUJ PI~!d 'l~h l~d ()()()t$ hI~llllII!XOlddll S! I~uullq:l Sfijl UO ~UllU~lUJllm 'lllllS hlP l~d '~lll Sfijl UJ m~IqOld ~l~A~S lsom ~ql ~U!l~llOO }O s~old ~ql UJ hIlU~lln:l S! l~UM.O hll~dOld S!lll ( l: OOO'6LZ'1$ t 3:SVHd 'IV.LO.L 000'9Z $ ~UtrI }{MllH I ~l!S ~OOO'~I $ UO!SOl~ ~UJsnll;) ~~llUJlllP 10{l~AO - pllO'M Iooq:lS I;)ql;)H }O quou hI~lll!{Y.)WW! hllllnq!lJ.. (3M'lN) 9D mll~llS ( $ I;)UUllq:l ~UOIll SWlll hqSlllW (3M'lN) 9D m~llS (~dOIS ;)P!S ~l~l:lUOO) l:OOO'~OV $ I;)uullq;::> pOOM.}{llld )I ;)l!S OOO'o€~ $ ~1J!UJ'l ;)l;)l:lUO;) - I;)uullq;::> ;)~P!lPOOM. o ~l!S 000'09 $ II ;)~lllS - l~l;)MOPllqSIIIOU)l hpUllS f ;)l!S 000'€9 $ II ;)~lllS - ~UtrI SJfOOlH ;::> ;)l!S (l~llS II~q:llM) pllO'M tOOO'ZZ $ II;)ddO;) }O m~llSUM.Oa UO!S0l3 ID m~llS UOn:lnllSUO;) ooo'on $ II ~~lllS - UO!S!A!pqns SM.OP~W W ;)l!S OOO'gz $ II ;)~lllS - ;)UtrI }~I;)IdllW d ~l!S 'S!Sllq {Y.)~U Sll Ull uo ~pUtlJ Slu~m~AOldm! IllUOmppll pUll ~lOl!Uom ;)q PInoqs SWlll ;)~qJ.. ';)mn Sfijl III lU;)m;)AOldw! lO} {y')PU;)WWOO;)l 10U ;)lll pUll ~UJllll hl!lO!ld MOl hl;)A II ~A!~~l q:lJqM Sl:l~rOld ;)lll {Y.)pnpUJ OSIV 'l~UM.O hu~dold ;)ql hq lO ~Sllqd sno!A~ld UJ {Y.)qS!IdWOO:lll u~q hP~lIll ~^llq SlU~m;)AOldW! ~mos ;)l;)qM Sl~rOld }O SlS!SUOO V ~Sllqd UOnlllU;)m~Idu:q V ;)Sllqd 'V 5. Phase 5 Implementation Phase 5 consists of projects which will probably be funded during the course of adjacent land development or as part of the thoroughfare program. Stream G 1 Coppell Road Stream G 1 Bethel School Road Grapevine Creek Site A Site H Site G Site L Grapevine Creek Stream G1 Stream C1 Stream D1 Cottonwood Branch Site N Erosion near LBJ Freeway Freeport Parkway near Southwestern Boulevard (Undersized storm sewer) Shady Dale Lane (culvert only) Whispering Hills/Sandy Lake Rd. Moore Rd. Drainage Improvements Belt Line Road Improvements Bethel Road State Road (Freeport Parkway) Coppell Road Culverts State Road - Freeport Parkway MacArthur/Sandy Lake Road TOTAL PHASE 5 $ 488,000 $ $ $ 555,000 400,000 280,0001 $ 39,000 $ 56,000 $ 249,000 $ 560,000 $ 426,000 $ 60,000 $ 118,000 $ 750,000 $ 12,000 $3,993,000 Recommendation not made; less expensive alternative shown for comparison. 6. Phase 6 Implementation Phase 6 recommendations generally preserve or enhance the existing channels and flood plains of the City of Coppell but may not reduce the flooding of any existing structures. Also included are recommendations which benefit the city overall although not directly flood plain or flood control related. Parallel Parkway System Greenbelt Preservation/Open Space Acquisition Hike and Bike Trail Additions City-Wide Survey Monumentation System TOTAL PHASE 6 $2,700,0001 286 acres $ 880,OOOZ $ $3,580,000 1 Estimated cost is total project cost. Developer participation is probable but is not estimated. 2 Estimate for ten foot wide concrete trails. 3 Information provided to city staff separately. VIII -7 8-IIIA reUOnRN ~q1 mOl} JY.}M~!^ U~qM 'SlSOO 1Y.)f01d ~U!~X~ Sl!J~u~q 1:l~f01d JO 1u~m~l!n}y.)1 IR1~JY.}J ~lll .Sl~U!~U3 JO SWOJ A11I.IV .s.n ~q1 q~nOlq1 !n{lOM I011UOO pooIJ 10J SPUI\j ~P!^Old OSIR 1U~mw~^0~ IR1~JY.}J ~lll .MRI Aq JY.}MoIIR SR 1~1~1U! ~U!lR~q SlU~mnR1SU! 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Additional details of federal assistance for flood damage prevention can be obtained from the Planning Division, U.S. Army Engineer District, Fort Worth. None of the alternative solutions in the Coppell City-WuJe Storm Water Management Study are likely candidates for this type of federal funding. r- , ~ 1 '......) ....., i \ Dallas County funds are also a possible source of revenue. However, drainage projects funded by the county are usually associated with street or thoroughfare improvements. In Coppell, Belt Line Road, Sandy Lake Road, MacArthur Boulevard, Denton Tap Road, Freeport Parkway and Royal Lane are considered major thoroughfares. If and when roadway improvements are planned for any of these streets, at least some of the drainage improvements recommended in this study could be included. o r-, . f I i ~-' Community Development Block Grants are also a source of funding. These grants are limited to a maximum of $300,000 per year. A community such as Coppell would compete with other communities for such funds. These proposed drainage improvements could qualify by eliminating community-threatening conditions and improving existing neighborhoods. A complete list of all requirements and application procedures can be found in Dallas County Community Block Grant Program - Policies, Procedures, and Application Information, February, 1990. o .-, C D. Conclusions rt The City-WuJe Storm Water Management Plan was approved by the Coppell City Council on January 29, 1991 (see Appendix B). The basic plan includes flooding site alternatives along the stream channels and miscellaneous local drainage problem sites compiled from citizen complaints. Also included in the plan are basin wide alternatives such as open space preservation and hike and bike trails to provide the city with an overall flood plain management plan, as well as, flood relief for individual flooding sites. During the course of this study, Albert H. Halff Associates, Inc. was asked to review the city's flood plain ordinance to determine if this ordinance provides adequate protection for the new developments within the city. This review was provided to city staff separately, however, adoption of additional criteria for flood plain development is included in Phase 1 of the Implementation Plan. Funding alternatives are discussed and it is recommended that the city pursue alternative sources of funds through the county for thoroughfare improvement and by establishing a municipal drainage utility fee. The implementation of the recommended storm water management plan will provide the City of Coppell with increased protection from flooding and will help to preserve a valuable natural resource for future generations. L.) r j ! I ~."".,.J n , ! L r, j ~ LI fl L; r") I I ...) .--. 1 ! 1",' ,-, , ! J , \-j r---, ~ I, , I L ,--., j ; : ~ ......} ,-.. , . VIII-9 ~I IX. GLOSSARY OF TERMS Alluvium - The clay, silt, sand, gravel, or similar detrital material deposited by running water. Antecedent Moisture Condition (AM C) - A measure of the degree of wetness of a watershed at the beginning of a storm. Backwater - The increase in stage, or elevation of the water surface, on the upstream side of a bridge, culvert, other hydraulic structure, object, or deposit above that which would occur in the absence of the structure, object, or deposit. Basin - Drainage of watershed area. Biota - The flora and fauna of a region. Bottomland - The low-lying land along a watercourse (usually used in plural). CFS - Abbreviation for cubic feet per second, which is a unit of water flow. Clayey - A soil composed chiefly of clay, which is an earthy material, plastic when moist but hard when fired, that is composed mainly of fine particles of hydrous aluminum silicates and other minerals. Cross Section (of a stream or valley) - In flood plain studies it is determined by a line approximately perpendicular to the main path of water flow, along which measurements of distance and elevation are taken in order to define channel and flood plain geometry. Design Flood - In Coppell, the design flood is the lOO-year flood based on a fully developed watershed. The regulatory flood plain is that area inundated by the design flood. Design Flood Plain - The area inundated by the design flood, assuming existing channel, bridge, and flood plain conditions. Detention - The use of a surface water runoff storage facility to hold (detain) surface water temporarily during and immediately after a runoff event. Discharge - As applied to a stream, the rate of flow, or volume of water flowing in a given stream at a given place and within a given period of time, usually quoted in cubic feet per second (cfs) or gallons per minute (gpm). Drainage Area - The area draining into a stream at a given point. The area may be of different sizes for surface runoff, subsurface flow, and base flow, but generally the surface runoff area is used as the drainage area. Drainage Subarea (Subwatershed) - Small drainage area used in detailed flood plain information and management studies. Typically many subareas (subwatershed) comprise the overall drainage area. Ecology - Pattern of relations between organisms and their environment. 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MOU l:JRllsqo q:JJqM ~lnl:JRllS 10 S~A;)1 'IIB - lU;)Wq:JR01:JU3 Fully Developed Land Use - The projected land use, assuming the basin is fully developed as planned. The City of Coppell's Future Lane Use Plan zoning was used for the fully developed scenario in this study. Greenbelt Preserves - Areas of scenic and environmental significance identified for preservation. These sites may be acquired by either purchase, dedication, or gift. HikelBike Trails - 10 foot wide concrete paths through a watershed for recreational use. Hydrograph - A graph showing, for a given point on a stream or for a given point in any drainage system, the discharge, elevation, velocity or other property of water with respect to time. Land Use - A land classification which indicates the manner in which a portion of land is being or will be utilized. Latitude - Angular distance north or south from the earth's equator measured through 90 degrees. Loamy - A soil consisting of a friable mixture of varying proportions of clay, silt and sand. Longitude - The arc or portion of the earth's equator intersected between the meridian of a given place and the prime meridian (as from Greenwich, England) and expressed either in degrees or in time. Mean Sea Level - The level of the surface of the sea at its mean position midway between mean high and low water. Meridian - A representation of a great circle or half circle on the surface of the earth passing through the poles numbered for longitude on a map or globe. Nature Trails - 8 foot wide gravel or other flexible base material trails for hiking only which travel through scenic and environmentally significant flood plain reaches. 100-Year Flood - A flood having an average frequency of occurrence on the order of once in 100 years at a designated location, although a flood of this magnitude may occur in any year and possibly in successive years. The 1oo-year flood has a 1 percent chance of being equalled or exceeded in any given year. In the past, this flood has been referred to as the Intermediate Regional Flood. 1oo-Year Flood Plain - The area inundated by the 1oo-year flood based on fully developed land use in the watershed and existing channel, bridge, and flood plain geometry. Parkways - Thoroughfare or local street paralleling the stream which provides access and creates buffer zones between the flood plain and development. This buffer zone provides a clear transition between natural areas which may be subject to flooding and areas of other land uses. Parkway with Swale - A parkway (street) on each side of an earthen channel. This is a channelization alternative for the streams which would allow some flood plain reclamation. The parkway with swale concept provides a more environmentally pleasing solution to the urban drainage problem. Current legislation for regulation of storm water point source discharge may encourage channel treatments such as this. Private Flood Plain - Reaches of the flood plain which are currently developed under private ownership and/or will be developed privately under prior agreements with the City of Coppell. IX-3 tr-XI '(SS61 'S~la At!Sl~A!Un UOloolJ!la :~Sl~f M~N 'UOloolJ!la) 'SPOOJ.!/ 'U!~qgUlrl '8: l~lIRM. pUR "0 mRTITIM. 'lAOH '(6861 'suos W A~nM. :}{10A. M~N) Ju,JlUaSvUVW.JaJVA1 a:mJ.ms uvq.Lfl "0 URnlS 'q~IRM. 'SRX~~ 'SRnRa 'lU~mURd~a SOOJnO~'M l~lRM. '~lRpOSSV IDRH 'H U~q1V '(1861 'sn~snq:msSRW 'PI~WilJ!ldS) 'uompg qlOS1 'tUVuO!J:J!a aJUJSallo:J MaN s,.JaJsqaA1 'AURdmo;) mRfll~W 'J pUR '0 ~Q 'Ql-ZZ qgn01ql 1-ZZ 'dd '(ZL61 'oomo gU!llJ!la lU~mw~AOO ~lms ~l!Ufl :'J'a 'UOlgU~SRM.) '&O]O.LplH 'I' uO!J:Jas 'J[ooqPUVH SUf.L3au!fJU:F[ ]VUO!JVN S:JS 'oo!Al~S UOHRAl~SUo;) nos '~Jnlln:>~v )0 lu~mURd~a ~lRlS ~l!Un :OOlnos 'm~lsAS ~gRU!R1P 10 m~llS R Aq ~U!R1P ~lR ~Q - ~qSl~lRM. 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SJ{lRd '~Al~~ld ~lnlRU SR :>TIqnd ~ql Aq ~sn 10) ~Al~~ld pUR Atp ~ql Aq ~UMO PUlrl - OORdS u~dO :>!Iqna X. END NOTES Chapter I (1) North Central Texas Council of Governments, Regional Data Center, 1990 Current Population Estimates for the North Central Texas Region, (Arlington, Texas: NCTCOG, May 1990). (2) City of Coppell, Comprehensive Plan, (Coppell, Texas: City of Coppell, Approved February, 1987), p. i. (3) Dallas Morning News, January 27, 1991, p. 22A (4) American Water Resources Association, HYDATA, Volume 7, No.3, (May 1988), p. 2. (5) U.S. Army Corps of Engineers, Fort Worth District, Report on Flooding May-June 1989 (Fort Worth, Texas), pp. 1, 17. (6) U.S. Geological Survey Water-Data Reports, Water Resources Data Texas, Water Years 1962-1987. (7) Federal Emergency Management Agency, Flood Insurance Study, City of Coppell, Texas, Dallas and Denton Counties (February 15, 1984), p. 5. (8) United States Army Engineer Districts, Fort Worth and Galveston, Texas, Corps of Engineers, Flood Plain Information Tenmile Creek, Dallas County, Texas, prepared for the City and County of Dallas, Flood Control Committee (Fort Worth, Texas: U.S. Army Corps of Engineers, May 1968), p. 26. (9) Federal Emergency Management Agency, Flood Insurance Study, City of Coppel~ Texas, Dallas and Denton Counties (February 15, 1984), p. 5. (10) U.S. Army Corps of Engineers, Fort Worth District, Upper Trinity River Basin, Trinity River, Texas, "Common VISion" (March 1990), pp. 3-2 through 3-3. (11) U.S. Army Corps of Engineers, Fort Worth District, Report on Flooding May-June 1989 (Fort Worth, Texas). (12) Trinity Improvement Association, "Flood Damages Show Need for Action", TA Update, 90-06 (Irving, Texas; Trinity Improvement Association, June 1990) p. 1. (13) U.S. Army Corps of Engineers, Fort Worth District, Report on Flooding April-May 1990 (Fort Worth, Texas), p. 62. (14) Ibid, p. 34. (15) Texas State House of Representatives Document Number 403 (HD No. 403), "Trinity River and Tributaries, Texas" (October 2, 1941). (16) Texas State House of Representatives Document Number 276 (HD No. 276), "Trinity River and Tributaries" (August 25, 1965). X-I Z-X "S€-OJPhH SA\N 'salfJ1S PCJ1!UIlIV.I1uCJ::J puv ULCJlstJ'3 CJt{l.l0J hUCJnbCJ.l.!! uopv1!dpCJ.lJ CJlnU!W-09 01 CJt1.!.!! ~JP:)Iy')Jd (v) "01' "ON .lCJdVcI JV:J!ut{:JCJ.L 'PI:)yqSJ:)H (E) "(S861 'J:)lU~ 1l11l0 JIlll1lITI;) IllUOIlllN :llUTIOJll;) quoN ':)1TI^:)qsy) stJxtJ.L 't{1.loA11.lo.!!-svllva 'VIVa CJt1.pV.lvdwo::J t{1!M tUvwwns lvnuuy fr86l !V1Va IV:J~OIOIVW!l::J JV:J07 'UOIlllJ1SfU!UIPV Jp:)qdsowlV put! JJU~O It!UO!lt!N (z) "L€-AI q~nOJql I-AI odd '(9L61 hJllnUllf '"JUJ 'S:)lt!POSSY mllH "H U:)qIV :!rnX:)].. 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'Slll1110) "JUI ':)J~O pUll UO~J:)d 'uonJPPV SPUllIPOOA\. :)}{1rI quoN JOJ 'stJxtJ.L '1ICJddo:JJo At!;] ''fCJCJ.l:J CJu!t1.CJdv.lD 'UopVCJU!ICJa U!olcI pooH .loJ vIva :J!lnV.lplJ[ puv ~OIO.lP^-H IlJ!1.locI 'SJ~~U3 '"JUJ 'S:)lllPOSSY mllH "H ll:)qIV (6t) "(P861 'SI hJllnJQ:)d) SCJ!1uno::J U01UCJa puv sVlloa 'stJxtJ.L '1ICJdtlo:J Jo M!:J 'ApmS CJ:JUV.lnsu/ POOH 'hJu:)~V lU:)W:)~llUllW hJU:)~J:)W3 IllJ:)~d (sO "L-l "d 'J CJwnloA uUO!SJA uowwO;)u 'svxtJ.L '.lCJt1.!H At!UJ.l.L 'U!SVfl .lCJt1.!H At!UJ.l.L .lCJddIl 'S].JodCJ~ CJ:JuvsSlvuuo:JCJ~ 'lJplSJO quoA\. UOd 'SJ~~U3 JO sWO;) hWJV "S"n (al (5) Kimley-Horn and Associates, Inc., Coppell Master Drainage Study. (6) Conversation and correspondence with Calvin M. Johnson of the Soil Conservation Service South National Technical Center in Fort Worth, October 8, 1987. (7) Hershfield, Technical Paper No. 40. p. 2. (8) Halff, Hydrology and Hydraulics of Flood Plain Studies, p. IV-16. (9) United States Department of Agriculture, Soil Conservation Service, SCS National Engineering Handbook, Section 4, Hydrology (Washington, D.C.: United States Government Printing Office, 1971). (10) Halff, Hydrology and Hydraulics of Flood Plain Studies, pp. IV-26 through IV-29. (11) United States Army Corps of Engineers, Fort Worth District, NUDALLAS - Documentation and Supporting Appendices, (Fort Worth, Texas: U.S. Army Corps of Engineers, September 1986), pp. 33-36. (U)Jaromir Nemec, Engineering Hydrology (London, England: McGraw-Hill, 1972), p. 275. (13) Ray K. Linsley, Jr., Max A Kohler, Joseph L. H. Paulhaus, Hydrology for Engineers (New York, New York: McGraw Hill, 1958), p. 220. (14) Walter B. Langbein, "Storage in Relation to Flood Waves," in Hydrology, Edited by Oscar E. Meinzer (New York, New York: Dover Publications, Inc., 1942), p. 570. (15) John E. Schaufelberger, Colonel, U. S. Army Corps of Engineers, "Record of Decision, Regional Environmental Impact Statement - Trinity River and Tributaries" (Fort Worth, Texas: U.S. Army Corps of Engineers, April 29, 1988). . (16) United States Army Corps of Engineers, Fort Worth District, Draft Regional Environmental Impact Statement - Trinity River and Tributaries (Fort Worth, Texas: United States Army Corps of Engineers, May 1986). (17) Kimley-Horn and Associates, Inc., Coppell Master Drainage Study. r-- (18) United States Army Corps of Engineers, HEC-2 Water Surface Profiles, User Manual (Davis, California: United States Army Corps of Engineers, Hydrologic Engineering Center, May 1985). (19) U.S. Army Corps of Engineers, HEC-l. Flood Hydrograph Package, Users Manual. (20) Paul K. Rodman, "Effects of Urbanization on Various Frequency Peak Discharges," for Fall Meeting Texas, New Mexico, and Mexico Sections, American Society of Civil Engineers, October 1977. (21) United States Army Corps of Engineers, Snyder Method for Deriving Unit Hydrographs (Davis, California: United States Army Corps of Engineers, Hydrologic Engineering Center, June 1974). (22) Federal Emergency Management Agency, Flood Insurance Study, City of Coppell, Texas, Dallas and Denton Counties (February 15, 1984), pp. IP-15P. X-3 v-x "8Z "d '"P!q] (n) oSZ od (Sl;'r.)tqgUg }O SWO;) AUllV os on :smc~.L 'qUOM. Uo"~:r) StJ'!"LVJnllJ.l.L puv .J,MJH A1lUf.L.L - IUtJWtJlVIS pvdw[ IVIUtJWUO.l!AU'H IVU~tJH J/v.J([ '1:>P1S!0 qUOM. UOd 'Sl;'r.)~Ug}O SWO;) AUllVOS"n (n) oop '6Z odd '(UOJlJP3 pu~s S8611~qOl:>O 'V8611~qW~~0 'kmMl~suO;) ~lnlBN SBX~.L ~U) tJt\.JtJStJ.Ld IStJ.JOd JftJtJ.J:J ~Uf.LdS 'A:>UBi\l~SUO;) ~lnlBN SBX~.L ~u (n) "ZSv od '(ZL61 'ss~ld ~gn~ld 'UOJlJP3 pUZ) svXtJ.L vtJ'/vl{J.10M J.10d-SVllva tJl{lfo v.JoH ~Uf.LdS s.JtJuUll{S 'Sl~UU!qS oH pAOn (~1) "Z01-v6 odd '(OS61) lOON 'z "lOA 'tJ:Ju"!:JS fo IVULnO[ svXtJ.L tJl{.L '.smc~.L}O ~UJAOld :>nom ~Uu '.qBIH ){UB1d oM. 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UOd 'Sl;'r.)U!gUg }O SdlO;) AUllV ~lB1S ~l!Un (E) "on -801 odd '(8L61 '0:>UJ: 'suos pUB A~HM. uqor) MStJ.JOd uvq.Lfl '~){~U~O T ){:>pP~ld pUB 'A~lD "M. ~U~D (z) "LL1-€91 odd '(SL61 'UOnBIOWO;) OI~H "H"V :smc~.L 'SBIIBO) LL6l-fJL6l tJp!no 11J!.L1snPU[ tJJVIS puv :JvuvWIV SVXtJ.L 'SM~N gtqUlOW SBIlBQ (J) ill .Jatdoq;) (18) Ibid, p. 28 (19) U.S. Army CorpS of Engineers, Fort Worth District, Reconnaissance Report, Upper Trinity River Basin Trinity River, Texas "Common VLSion", DRAFT (Fort Worth, Texas: U.S. Army Corps of Engineers), p. 2-7. (20) Lou Duggan and Jean Murph, eds., The Citizens Advocate Journal of Coppell History, Book 1, Centennial Edition, 1890-1990 (Coppell, Texas: Citizens Advocate, April 1990), p. 37. (21) Ibid., p. 37. (22) City of Coppell, Texas, Comprehensive Plan (Coppell, Texas: City of Coppell, February 1987), p. i. (23) The University of Texas at Austin, Texas, Archaeological Research Laboratory, Archaeological and Historical Surveys (Austin, Texas: Balcones Research Center, July 1990). (24) Claude C. Albritton, Jr. and L. Gary Pattillo, Jr., "A Human Skeleton Found Near Carrollton, Texas," reprinted from Field and Laboratory, Vol. VIII, No.2 (Southern Methodist University Press, May 1940), pp. 59-64. (25) Wilson W. Crook, Jr., "The Wheeler Site: A 3500 Year-Old Culture in Dallas County, Texas", Field and Laboratory, Vol. XX, No.2 (Southern Methodist University Press, April 1952), pp. 43-65. (26) Lou Duggan and Jean Murph, eds., The Citizens Advocate Journal of Coppell History, pp. 5 through 7. (27) Ibid., p. 37. (28) Ibid., pp. 35, 36. (29) Ibid., p. 35. (30) City of Coppell, Texas, Comprehensive Plan, p. 15. (31) North Central Texas Council of Governments, Regional Data Center, 1990 Current Population Estimates. (32) Dallas Morning News, January 27, 1991, p. 22A (33) Ibid., p. 22A (34) Citizens Advocate, October 5, 1990, pp. 1-4. (35) City of Cappell, Texas, Comprehensive Plan. (36) Ibid., p. 50. X-5 9-X 'Pl-IA qgnO.Iq1l-IA 'dd '(9L611~qm~a ":lUJ 'S~}l~pOSSV m~H 'H u~qIV :SllX~.L '~rr~a) ~rr~a JO AlD ~q1 10J {Y.)l~d~ld 'I tJwnloA 'JftJtJ.1:J tJl!wtJtlH Jo lutJwtJ2tJutJjf UJtJlcl pooH ":lUJ '~l~POSSV m~H 'H U~qIV (1) AI .I31deQ::> '(6861 .u~lq~d 'SUO!l~rrqnd DO:::>.LJN :SllX~.L 'u01gurrlV) Z6-6861 N!ltJn() DltJ.M tu.L01S utJq.1fl 2lf!JitJutJjf .1oJ &JtJltJ.lJS ItJuqJitJN 'SlU~WUl~^OD JO TpunO:) SllX~.L l~llU~ quoN (IS) '9S-0S 'dd '(8861) 1 'oN '09 'loA 'uoptJ.1tJPtJd 10.lJuo:J uopnlloclDltJ.M ItJwno[ ..~gl~q:lSJa ~lnos 1Q!od 1~1~A\ Wl01SJO UO!l~lng~'Mu 'S:l!WO)l 'f 'f (OS) '869Z 'd '(8L61) OS 'loA 'uoPtJDPtJd 10.lJuo:J uopnllocl .1tJltJ.M ItJwno[ u'l!OAl~~'M ^lddns 1~1~A\ ~ uo 1011UO:) m~llsdfl JO Sl~lJ3u "l~ 1~ 'rr-epu~'M 'A\':::> (6~) 'S6 'd '(9861 ':::>A\.L :~x~.L 'Q!lsny) sp.1tJputJJs NJzvn() .1tJltJ.M tJ;JtJjms stJXiJL '(:)A\.L) UO!sS!WWO:) 1~1~A\ ~x~.L (sp) 'M7 'd 'stJJ.LtJmqJ.LL putJ DtlRI NJUJ.LL - lUtJWtJltJ1S PtJdWI ZVlutJwuo.lJtlUH zvuo?1itJN JjtJ./G 'Sl~U!gu3 JO SWO:) ^WJV 'S'fl <L~) '8 'd '(0661 fildy '~l~POSSV u~mq:lSV-uou~g :SllX~.L '~n~a) JjtJ./G 'lltJddo:J Jo ND tJ'll.1OJ sp.1tJputJJs uJi!stJa putJ suoptJ:Jif!sstJl:J zvuop:Jund MJMPtJON ":lUJ '~l~POSSV U1~mq:lSV-Uou~g ~) 'Z-f 'd 'II tJwnlOA uUO!SlA UOWWO:Ju 'StJXiJL '.1tJtl!N N!UJ.LL 'u!StJfl DtlRI NJUJ.LL .1tJddfl 'sJ.lodtJN tJ:JUtJSSltJUUO:JtJN '1:lp1SJa qUOA\ UOd 'Sl~U!gu3 JO SWO:) ^WJV 'S'fl (S~) 'Lp 'd 'uvlcl tJtl!sutJ'ltJ.1dwo:J 'rr~ddO:) JO AlD (>>) '(Z861 .u~nJq~d 'rr~ddO:) JO AlD :SllX~.L 'rr~ddO:)) UtJlcl uopVtJ.l:JtJN putJ J/.1Vcl 'n~ddO:) JO AlD (E~) '617 'd '(0861 'q:llllW :SllX~.L '~rrlla) 'unO:) Sl~UO!SS!WWO:) AlunO:) ~rrlla ~q1lOJ {Y.)llld~ld 'utJlcl tJ:JtJdS utJdO Nuno:J stJlltJa '~n!WWO:) glJ!U1l~ld ~lldS u~dO AlunO:) ~rr~a (Z~) '681 'd '(6S61 'fildy '~nlla JO AlD :SllX~.L '~rrlla) 'vtJ.LY uV1!l0do.lJtJjf sVllva 'stJ:JtJdS utJdO putJ SJ/.1Vcl 'UO!l~l~'M pUll S)f1lld JO 1u~mUlld~a pUll gU!UUllld Ullqlfl JO 1u~mUlld~a 'SllX~.L '~nlla JO AlD (1~) 'f: 'd '(SL61 '~unf) 'StJtJ.LY ItJ:J?JJ.L:J tJ'll 2UJ,(flJUtJPI tJ:JtJdS utJdO 'SlU~WUl~^OD JO [punO:) SllX~.L l~llU~ quoN (~) , stJltJtupsH uoptJlndocllutJ.un:J 0661 'l~lU~ 1l1~a lllUO~~'M 'SlU~WUl~^OD JO IpunO:) SllX~.L lllllU~ quoN (6E) 'f: 'd '(0861 'q:ll~W :SllX~.L '~rrlla) unO:) Sl~UOJSS!WWO:) AlunO:) ~rrlla ~q1lOJ {Y.)l~d~ld 'UtJlcl tJ:JtJdS utJdO .o.uno:J stJlltJa '~n!WWO:) glJ!U1l~ld ~~dS u~dO AlunO:) ~rr~a (lIE) 'OS 'd "P!C/! <LE) (2) City of Coppell, Texas, Subdivision Ordinance (Coppell, Texas: City of Coppell, November 1985), Appendix A, pp. 25 through 30. (3) Roy F. Weston, Inc., A Manual on Storm Water Management for Evaluating and Mitigating the Effects of Land Use Changes in Runoff, prepared for the Maryland - National Capital Park and Planning Commission, Silver Spring, Maryland (West Chester, Pennsylvania: Roy F. Weston, Inc., June 1974), p. 17. (4) Department of Urban Planning, City of Dallas, Texas, Design Guidelines for Developing Areas, draft (Dallas, Texas: Department of Urban Planning May 1976), p. 66. (5) Halff, Flood Plain Management of Fivemile Creek, Volume I. (6) Vujica Yevjevich, "Systematization of Flood Control Measures," Journal of the Hydraulics Division, Proceedings of the American Society of Civil Engineers, Volume 100, Number HYll (November 1974), p. 1542. (1) Weston,op. cit., p. 11. (8) Merwin D. Dougal, ed., Flood Plain Management: Iowa's Experience (Ames, Iowa: The Iowa State University Press, 1969), pp. 69, 70. (9) Weston, op. cit., p. 24. (10) Dougal, op. cit., p. 71. (11) Ibid., p. 71. (12) John R. Sheaffer, Introduction to Flood Proofing: An Outline of Principles and Methods (Chicago, Illinois: The Center for Urban Studies, University of Chicago, April 1967), pp. 1-3. (13) Weston, op. cit., p. 43. (14) Halff, Flood Plain Management of Fivemile Creek, Volume I. (15) Thomas J. Jackson and Robert M. Ragan, "Hydrology of Porous Pavement Parking Lots," Journal of the Hydraulics Division, Proceedings of the American Society of Civil Engineering, Volume 100, Number HY12 (December 1974), p. 1751. (16) Department of Urban Planning, City of Dallas, Texas, Design Guidelines for Developing Areas, draft, p.67. (11)Weston, op. cit., p. 19. (18) Herbert G. Poertner, Practices in Detention of Urban Storm Water Runoff, American Public Works Association, Special Report Number 43 (June 1974), pp. 43, 44. (19) Weston, op. cit., p. 31. (20) Poertner, op. cit., pp. 43, 44. X-7 8-X VZZ .d '1661 'LZ ,(Itmu~r 'SMdN 2UJUlOW sV/JVa (~) .saJvutpsH uopV/ndocl Jua.un;) 066l 'SlmnUUlgAOD JO {pun OJ smcgJ.. l~llU~ qlloN (E) .1 .d '(t861 '~1 ,(mDlqgd) sapuno;) uOJuaa puv sV/JVa svxtJL 'lladdo;) Jo M!;J ',(pms a:Juv.lnsu/ pooH 'k>Ug~v lUgmg~~u~w k>Ug~lgm3 l~lgpgd (z) .917-8: .d '(0661 'q:)l~W) sa:J!puaddV - II awn/o/! .uO!S'lA UOWWO;). svxtJL '.lat\!H M!UJ.LL 'UJsvg ot\!H M!UJ.LL oddfl '1:>!l1S!0 qllOM. llod 'Sl~Uf.lU3 JO sdJOJ ^WlV .s.n (1) IA .I3ldoq:J .(.p.u 'ngddOJ JO At!;) :smcgJ.. 'ngddOJ) (pgl~dn) UVlc/ adv:JS1aa./.1S 'smcgJ.. 'ngddOJ JO At!;) (6) .J?:J .do '.:>UJ 'sgl~POSSV umuq:>SV-UOll~8: (8) .LZ-V .d '8L61 'u ^~W 'p/v.laH salU!L SV/JVa ([J .m-IA q~nOlQl E-IA .dd '(8L61 19qmgldgs '.:>UJ 'sgl~POSSV m~H .H llgqW :smcgJ.. 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'ngddOJ JO At!;) (El) .017-EE .dd '.l'!lJ[ (zz) .6Z .d '.l'!lJ[ (lZ) (5) City of Cappell, Comprehensive Plan. (6) Schaufelberger, op. cit. (7) Albert H. Halff Associates, Inc., White Rock Creek Flood Plain Management Study (Dallas, Texas: Albert H. Halff Associates, Inc., December 1989). (8) City of Austin, Texas, Engineering Department, Drainage Criteria Manual (Austin, Texas: City of Austin, June 1988), p. P-l. (9) City of Cappell, Texas, Comprehensive Plan, pp. 53-56. (10) Schrickel, Rollins and Associates, Inc., Coppell Hike/Bike Plan (Cappell, Texas: Schrickel, Rollins and Associates, Inc., January 22, 1985), Figure 25. (11) Dallas Times Herald, May 11, 1978, p. A-27. (12) R.K. Linsley, Jr., M.A Kohler, Vol. H. Paulus, Hydrology for Engineers (New York, New York: McGraw-Hill, 1958), p. 57. Chapter vn (1) Albert H. Halff Associates, Inc., "Preliminary Recommendations - Priority Local Drainage Problems for the City Cauncil of the City of Cappell," (Dallas, Texas: Albert H. Halff Associates, Inc., May 14, 1990). (2) City of Dallas, Texas, Drainage Design Manual. Chapter VIn (1) Halff, Flood Plain Management of Cedar Creek and Its Tributaries, pp. VIII-5, 7. (2) Ibid., p. VIII-20. (3) Citizens Advocate, August 31, 1990, p. 2. (4) Citizens Advocate, August 24, 1990, pp. 1, 5. X-9 XI. BIBUOGRAPHY Albritton, Claude C., Jr., and L. Gary Patilla, Jr. "A Human Skeleton Found Near Carrollton, Texas." Reprinted from Field and Laboratory, Vol. VIII, No.2, Southern Methodist University Press, May 1940. Allen, Peter M., and William D. Flaniga. "Geology of Dallas, Texas, United States of America." Bulletin of the Association of Engineering Geologists, Vol. XXIII, No.4, 1982. American Water Resources Association. HYDATA, Volume 7, Number 3, May 1988. Austin, City of, Texas. Drainage Criteria Manual. Austin, Texas: City of Austin, June 1988. Austin, City of, Texas, Engineering Department. Policy. Austin, Texas: City of Austin, 1985. Regional Storm Water Management Program Barton-Aschman Associates, Inc. Roadway Functional Classifications and Design Standards for the City of Coppell, DRAFT. Dallas, Texas: Barton-Aschman Associates, Inc., April 1990. Blair, Frank W. "The Biotic Provinces of Texas." The Texas Journal of Science, Volume 2, Number 1, 1950. Coppell, City of, Texas. Comprehensive Plan. Coppell, Texas: City of Coppell, February 1987. Park and Recreation Plan. Coppell, Texas: City of Coppell, February 1982. Streetscape Plan, (updated). Coppell, Texas: City of Coppell, n.d. Subdivision Ordinance, Ordinance No. 341. Coppell, Texas: City of Coppell, November 1985. Zoning Ordinance, Ordinance No. 297. through May 1, 1988. Coppell, Texas: City of Coppell, Updated Crook, Wilson W., Jr. "The Wheeler Site: A 3500 Year-Old Culture in Dallas County, Texas." Field and Laboratory, Vol. XX, No.2. Dallas, Texas: Southern Methodist University Press, April 1952. Dallas, City of, Texas. Drainage Design Manual. Dallas, Texas: City of Dallas, Spring 1990. Urban Storm Runoff Sampling Program, Storm of February 11, 1977. Dallas, Texas: City of Dallas, 1977. Dallas, City of, Texas, Department of Urban Planning. Design Guidelines for Developing Areas, draft. Dallas, Texas: Department of Urban Planning, May 1976. Dallas, City of, Texas, Department of Urban Planning and Department of Parks and Recreation. Parks and Open Spaces, Dallas Metropolitan Area. Dallas, Texas: City of Dallas, April 1959. XI-I Z-IX '6861 J:)qw:Y.):)a "JUI 'S:)l-epOSsy m-eH 'H U:)qIV :SID::).L 's-err-ea 'III-I 'lOA 'ApmS lU<JW<JfJvuvW uJVlcl POOH 'f<J<J.1J 'f:J0"H <J1!l/A1 --- '0661 '171 A-eW "JUJ 'S:)l-epOSSY m-eH 'H U:)qIV :s-ex:).L's-eu-ea :rr:)ddOJ 10 AlK:> :)qllo 1!JuoOJ AlK:> :)ql JOl sw:)1QOJd :)~-elI!-eJa l-eJO'1 AlJ.IO!ld - SUOH-epu:)wwOJ:)'M hlulJ!Wn:)Jd. --- '8L61 J:)qw:)AoN "JUJ 'S:)l-ePOSSY m-eH 'H lJ:)qIV :SID::).L 's-eu-ea ''f<J<J.1J <JU!t1dav.1D 'uopv<JU!pa U!vlcf pooH .1oj vIVa :mnv.1pAJ/ puv :J!fiolO.LpAJ/ IVJJ.Lvcf --- '9861 J:)qOlJO "JUJ 'S:)l-epOSSY JJl-eH 'H V :SID::).L 's-errua 'u:)11V 10 AlK:> :)ql JOl ~Jud:)Jd 'ApmS 'f.1Vcf lpqu<J<J.1D .1v<JU!7 "--- '9L61 hl"BOU-ef "JUJ 'S:)l-epOSSY JJl-eH 'H V :SID::).L 's-eu-ea 's-err-ea 10 AlK:> :)ql JOl ~J"Bd:)Jd 's<J!pnJS U!vlcl pooH jo s:J!lnV.1pAJ/ puv t<iJoIO.1pAH '--- '9L61 J:)qw~a "JUI 'S:)lUPOSsy mUH 'H V :SID::).L's-eu-ea 's-eu-ea 10 AlK:> :)ql JOl ~J"Bd:)Jd 'I :)woloA ''f<J<J.1J <Jflw<Jt\!.!f jo lU<JW<JfJvuvw U!vlcl POOH "--- '8L61 J:)qw:)ld:)s '"JUI 's:)l-epOSSY m-eH 'H V :s-ex:).L 's-euua 's-err-ea 10 AlK:> :)ql JOl ~J-ed:)Jd 's<JJ.LvmqJ.L.L SI/ puv 'f<J<J.1J .1Vp<JJ jo lU<JW<JfJvuvw U!vlcl pOOJ.':! "JUJ 'S:)l-epOSSY "H U:)qIV 'm-eH '8L61 "JUJ 'suos pu-e A:)TI& uqOf .tVJS<J.1Od uvq.1fl ':))}:)u:)a T )}J!l:)~Jd pu-e ,.& :)U:)O 'A:)JO "LL61 :)UOf ':Y.)J:)wwOJ 10 lu:)wu-ed:)a 's"n :PU-elhl-eW '~ll!ldSJ:)ATIS '~€-OJPAH SMN wopu-eJow:)w l-eJJuqJ:).L VVON 'S<J1V1S P<J1!ufllv./Ju<JJ puv u.msvH <Jl{1 .1oj hU<Jnb<J.1d uopv1!ap<J.Lcf <JmU!W-09 01 <Jt\!.!f 'UOJl-eJ1SJlI!WPV Jp:)qdSOW1V puu JJUl!:Y.>O l-euoHuN "H qdl-e'M ')}J!l:)~Jd "17861 '~1 hlUOlq:)d "s<J!1unoJ U01U<Ja puv SVllva 'SVXiJ.L 'll<JaaoJ jo ND 'ApmS <J:JUV.Lnsu/ POOH "A:>u:)~V lU:)W:)~uuuW A:>u:)~J:)wg lUl:)P:)d '0661 TIJdV ':)l-eJOAPV SU:)zHK:> :SID::).L 'U:)ddOJ '066l-068[ 'UOP!PH IV!UU<J1U<JJ '[ 'foofl 'tU01S!H ll<JaaoJ jo Ivu.mo[ <J1V:J0t\PV SU<JZ!JD <Jl{.L .~ 'qwoW uU:)f pu-e '00'1 'uu~oa :)Q.L :-eM.OI 'S:)UIV '<J:JU<J!Ddxg s, VMO/ '6961 'SS:)Jd AlJSJ:)AJUn :)l-elS -eM.OI :IU<JW<JfJvuvW uJVlcl pooH 'P:) "a uJM.l:)W 'l-e~OOa "~L61 'UOHUJOdJOJ 01:)8: 'HV :SID::).L 's-err-ea 'LL6[-9L6l '<Jp!nD IV!.lJsnpu/ <J1V1S puv :JvuvwIV SVXiJ.L 'SM.:)N ~UJUlOW s-err-ea '~961 J:)qw~a 'Al:)POS l-eJ~OlOOO s-err-ea :SID::).L 's-euua 'NunoJ sVllva jo t<iJoIO<JD <Jl{.L 'Al:)POS l-eJJ~OlOOO s-euua '0861 qJJUW :SID::).L 's-err-ea 'UOOJ SJ:)uoJSSJlUWOJ AluoOJ s-err-ea :)ql JOl ~J-ed:)Jd uod:)J U 'UVlcl <J:Jvas u<Jao NunoJ svllva ':)Q.L '~nJlUWOJ ~UJUU-eld :Y.)-edS u:)dO AluoOJ s-err-ea "8861 's-errua 10 AlK:> :SID::).L 's-euua 'SWV<J./JS sVllva jo tf3(\.Jns N!1Vn() .1<J1VA1 886l <Jl{1 uo 1.Loa<J"H V "uoHJ:)S lU:)WSS:)SSY l-elU:)WUOlJAug 'UOHJ:)lOJd J:)wosuOJ pu-e qll~H lU1U:)WUOlJAug 10 uOJSJAJa 's-ex:).L '10 AlK:> 's-err-ea Hershfield, David M., United States Department of Commerce, Weather Bureau. Technical Paper No. 40: Rainfall Frequency Atlas of the United States for Duration from 30 Minutes to 24 Hours and Return Periods from 1 to 100 Years. Washington, D.C.: U. S. Department of Commerce, May 1961. Ingram, William T., et aI., eds. Glossary - Water and Wastewater Control Engineering. Prepared by Joint Editorial Board representing American Public Health Association, American Society of Civil Engineers, American Water Works Association and Water Pollution Control Federation, 1969. Jackson, Thomas J., and Robert M. Ragan. "Hydrology of Porous Pavement Parking Lots." Journal of the Hydraulics Division of the American Society of Civil Engineering, Volume 100, Number HY12, December 1974. Kimley-Horn and Associates, Inc. Coppell Master Drainage Study. Horn and Associates, Inc., January 1990. Dallas, Texas: Kimley- Korpics, J. J. "Regulation of Storm Water Point Source Discharges.' Journal Water Pollution Control Federation, Volume 60, Number 1, 1988. Langbein, Walter B. 'Storage in Relation to Flood Waves," in Hydrology, edited by Oscar E. Meinzer. New York: Dover Publications, Inc., 1942. Linsley, Ray K., and Joseph B. Franzini. York: McGraw-Hill Book Co., 1972. Water-Resources Engineering, 2nd Edition. New Linsley, Ray K., Jr., Max A Kohler, Joseph L.H. Paulhaus. Hydrology for Engineers. New York: McGraw-Hill, 1972. Meyer, L. D., and M. A Ports. 'Prediction and Control of Urban Erosion and Sedimentation,' Proceedings of the National Symposium on Urban Hydrology, Hydraulics and Sediment Control, UKY BVIII, edited by Billy J. Barfield. Lexington, Kentucky: ORES Publication, University of Kentucky, December 1976. National Oceanic and Atmospheric Administration. Local Climatological Data; 1984 Annual Summary with Comparative Data, Dallas-Fort Worth, Texas. Asheville, North Carolina: National Climatic Data Center, 1985. Nemec, laromir. Engineering Hydrology. London, England: McGraw-Hill, 1972. North Central Texas Council of Governments, Population Estimates for the North Central Texas Region. of Governments, May 1990. Regional Data Center. 1990 Current Arlington, Texas: North Central Texas Council North Central Texas Council of Governments. Open Space Identifying the Critical Areas. Arlington, Texas: NCTCOG, June 1975. ---. Regional Strategy for Managing Urban Storm Water Quality 1989-1992, Draft. Arlington, Texas: NCTCOG Publications, February 1989. Standard Specifkations for Public Works Construction. Arlington, Texas: NCTCOG, August 1987. XI-3 trIX 'L861 l~qOPO {Y.}lm> uod~'M I1Hl!d '9861 AllW {Y.}lllP uod~'M lJll1a 'Sl~upiu3 JO sdlOJ AUUV 'S '0 :SllX~.L 'qUOA\ UOd 'saJ.LlJJn([!.L.L pulJ .l3l\m MJUJ.L.L 'JuawaJlJ1S PlJdw[ WJuawuo.lJl\u3 IlJUO~aH 'l:lPlSJa 'SllX~.L 'qUOA\ UOd 'sl~~UJgu3 JO SdlO;) AWlV S~llllS P~lJUO '1L61 'p1llOg lu~wdoI~^~a 1~11lA\ S'eX~.L :SllX~.L 'unsny '[II J.JlJcI 'SlJXiJ.L U! s.lJol\.I3saH pulJ SWlJa uo lJJ1Ja SUJ.LaaU~U3 --- '€L61 'p1llog lu~wdoI~^~a 1~11lA\ SllX~.L :SllX~.L 'unsny 'II J.JlJcI 'SlJXd.L U! s.lJot\.JasaH pulJ SWlJa uo lJJlJa SUJ.Laa~U3 'p1llOg lu~wdoI~^~a 1~11lA\ S'eX~.L '9861 ';)A\.L :SllX~.L 'unsny 'spllJpulJJS MUlJn() l;JJlJAf a:mJms SlJXd.L '(;)A\.L) UOJSSJWWOJ 1~11lA\ SllX~.L T1761 'z l~qOl:lO '(mv 'ON 'QH) mv l~qwnN lU~Wn:lOa u 'SllX~.L '~JlmnqJl.L pUll l~^rn AtJUJl.Lu '~^nlllU~~ld~'M JO ~snoH ~llllS SllX~.L 'S861 l~qOPO 'VS61 l~qW::Y.Y.)a 'A:lUllAl~SUOJ ~mlllN S'eX~.L ~q,L 'UOJlJPtI PUo:Y.}S 'at\.Jasa.JcI Jsal0,f Jfaal:J SUJ.LdS '~q,L 'A:lUllAl~SUOJ ~mlllN S'eX~.L 'UOnllpOSsy S}[10A\ :lnqnd Ull:lJl~WV :SJOUJill 'ogll:lJq;) 'v l~qwnN 'L€ ~wnIoA 'l~uod~'M Y A\dV ~q,L 'UlJlcI asuodsaH POOl.f SJ[ sanWA SlJlllJa 'uqof 'I~d!~.L . '0861 q:l1llW 'UlJlcI a:JlJds uadO Muno:J SlJlllJa '~lllpOSsy pUll sumo'M 'I~){:lJlq:lS pUll ~lllpOSsy pUll U!AlllW '1~gUJ1dS 'ZL61 'SS~ld ~gJl~ld 'uoJlJP3 puZ 'SlJXd.L 'l}a.LV lfJ.JoAf J.Jo,f-SlJlllJa alfJ ]0 lJl0l.f SUJ.LdS slauu!lfS 'H pAOn 'Sl~UUJqS 'L%1 IPdy 'ogll:lJq;) JO AtJSl~^JUO '~JPntS Ullq10 10J l~lU~ ~q,L :SJouffiI 'ogll:lJq;) 'spolfJaw pulJ saldpU!.JcI ]0 aU!lJno uv :Suifoo.JcI pool.f OJ uop:JnpolJu[ ''M uqof 'l~JJ~qS 'S861 'zz AlllnUllf ":lUJ '~lllpOSsy pUll SUJno'M 'I~){:lJlq:lS :S'ex~.L 'n~ddOJ 'UlJlcI ;))f!fI/tn[!H lladdo:J ':lUJ '~lllpOSsy pUll suffiO'M 'I~){:lpq:lS 'UOlgUJqS'e A\ '0861 l~qw~ld~S 'At~pOS ~mPflA\ ~q,L :';)'a 'uoJlJPtI qlv 'WnulJW sanbfulf:Ja.L JuawaSlJulJW a1!lPll.A1 'a P10JUllS 'ZlJUW~q:lS '8861 '6Z fl1dy 'Sl~UJgu3 JO sdlOJ AUUV 'S'O :S'ex~.L 'qUOA\ UOd u'~JlmnqJl.L pUll1~^rn AtJUJl.L -lU~W~lms l:llldWI IlllU~WU01JAu3 IllUOJg~'M 'uoJ~a JO p1o:Y.}'Mu 'Sl~UJgu3 JO sdlOJ AUUV 'S'O 'I~UOIOJ "3 uqof 'l~gl~qI~Jnllq:lS 'LL611~qOl:lO 'suoJms OOJX~W pUll ooJX~W M.~N 'SllX~.L ~Sl~upiu3 P.^D JO At~POS Ull:lJl~WV ~ql JO gUJ1~W nlld 10J ',{gOI01PAH ullq10 UO 11lUJW~S u's~glllq:lSJa ){~d A:lU~nb~ld snOJlllA uo UOnllZ!Ullq10 JO Sl:l~JJ3u ')I Inlld 'UllWPO'M '8L61 'OS 'JOA 'uoplJ.I3pa,f 10lJuo:J uopnllocI .l3J1JAf wu.mo[ u'lJOAl~~'M AIddns 1~11lA\ II uo I011UOJ W~llSdO JO Sl~JJ3u 'Ill l~ "A\ ';) 'nllpUll'M 'vL61 ~unf 'UOnllpossy S}[10A\ :lnqnd Ull:lJl~WV '€v l~qwnN uod~'M Ill~dS 'lfOUnH: laJlJAf UUOJS UlJQlfl ]0 uopuaJaa U! S;J:JfJ:JlJ.JcI '0 u~q1~H 'l~UU~Od ---. Report on Flooding May-June 1989. Fort Worth, Texas: U.S. Army Corps of Engineers, Fort Worth District. ---. Report on Flooding April-May 1990. Fort Worth, Texas: U.S. Army Corps of Engineers, Fort Worth District. ---. HEC-1 Flood Hydrograph Package, Users Manual. Davis, California: U. S. Army Corps of Engineers, Hydrologic Engineering Center, January 1985. _n. HEC-2 Water Surface Profiles, Users Manual. Davis, California: U. S. Army Corps of Engineers, Hydrologic Engineering Center, May 1985. Hydrologic Engineering Methods for Water Resources Development, Volume 3, Hydrologic Frequency Analysis. Davis, California: U. S. Army Corps of Engineers, Hydrologic Engineering Center, July 1974. NUDALLAS - Documentation and Supporting Appendices. Army Corps of Engineers, September 1986. Fort Worth, Texas: U.S. Reconnaissance Report - Upper Trinity River Basin, "Common VISion, " VoL 1 and 2. Fort Worth, Texas: U.S. Army Corps of Engineers, Fort Worth District, March 1990. Rowlett Creek Expanded Flood Plain Information Study, Dallas and Collin Counties, Texas: Volume III, Environmental Considerations. Fort Worth, Texas: U.S. Army Corps of Engineers, September 1978. ---. Southwestern Division, Report by Les Beard and Shin Chang. Generalized Skew Coefficients of Annual Maximum Streamflow Logarithms. March 1978. ---. Snyder Method for Deriving Unit Hydrographs. Davis, California: U. S. Army Corps of Engineers, Hydrologic Engineering Center, June 1974. United States Army Engineer Districts, Fort Worth and Galveston, Texas, Corps of Engineers. Flood Plain Information Tenmile Creek, Dallas County, Texas. Fort Worth, Texas: U.S. Army Corps of Engineers, May 1968. United States Department of Agriculture, Soil Conservation Service in cooperation with Texas Agricultural Experiment Station. Soil Survey of Dallas County, Texas. Washington, D.C., February 1980. _n. Soil Survey of Denton County, Texas. Washington, D.C., January 1980. United States Department of Agriculture, Soil Conservation Service. SCS National Engineering Handbook, Section 4, Hydrology. Washington, D.C.: U. S. Government Printing Office, 1972. Standards and Specifications for Soil Erosion and Sediment Control in Developing Areas. College Park, Maryland: U. S. Department of Agriculture, Soil Conservation Service, July 1975. XI-5 9-IX ovL61 J:)qw:)AoN 'nAH J:)qwnN '001 :)wnloA 'SC1;Jlf!JiuH ]!t1.J:) Jo Md!:xJS UlJ:J?L;JWV ;Jl{J Jo s~U!P;J;J:JO.lcI 'uO'!S'!t1.Ia s:JIlnlJJPtW ;Jl{J Jo IlJUJno[ :s:)Jn~w IOJ1UO;) pooH }O UO!l~:)lsASu .lr.>!rnA 'qJ!^:)~:)A ovL61 :)unf '.JlIl 'U01S:)A\. .d AO'M :llJUllAIASUU:)d 'J:)lS:)q;) 1S:)A\. .PUllIAJllW 'sgU!JdS J:)AHS 'UO!sS!WWO;) gUJUUllld pUll 'lJlld Illl!dllJ IllUO!lllN - PUllIAJllW :)ql JO} ~Jlld:)Jd 'jfounH U! 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P;J!O.lcI pJlJPUlJJS 0__- oOL61 Alnf 'AWJV :)ql }O lU:)WUlld:)O oS on :0;)00 'UO~UJqSllA\. 01091-Z-OTH IllnUllW J~~U3 'SPUUlJl{::J 10JJUO::J pOOl.!! JO u2IS;Ja :JJlnlJJPAH .--- .8L61 qJJllW 'AWJV :)ql}O lU:)WUlld:)O .S on :0;).0 'uOlgUJqSllA\. .'iT61-Z-OTH IllnUllW SJ~U!gU3 'S;J;Jt1.;J7 Jo UO!J:JnJJSUO::J pulJ u2IS;Ja .SJ~~U3}O }:)!q;) :)ql }O :)JillO 'AWJV :)ql }O lU:)WUlld:)o S:)llllS ~l!un APPENDICES APPENDIX A CI1Y OF COPPELL FLOOD PLAIN ORDINANCE NO. 87390 [Not Included - Currently Under Revision; On File With The City of CoppeD] APPENDIX B MINUTES OF SPECIAL CIlY COUNCIL MEETING JANUARY 9, 1991 ACCEPTANCE OF CIlY-WIDE STORM WATER MANAGEMENT PLAN MINUTES OF SPECIAL CITY COUNCIL MEETING JANUARY 29, 1991 The City Council of the City of Coppell met in special called session on Tuesday, January 29, 1991 at 7:30 p.m. for Work Session in the City Council Chambers of the town Center, 255 _ Parkway Boulevard, Coppell, Texas. The following members were present: Mark Wolfe, Mayor Bill Smothermon, Mayor Pro Tem Peyton Weaver, Councilman Tom Morton, Councilman Jim Cowman, Councilman Ron Robertson, Councilman John Nelson, Councilman Councilman David Thomas was absent from the meeting. Also present were City Manager Alan D. Ratliff and Assistant City Manager / Personnel Director Vivyon Bowman. Item 1: Call to order Mayor Wolfe called the meeting to order. Item 2: Invocation Council went directly into the work session without observing this item. Item 3: Pledge of Allegiance Council went directly into the work session without observing this item. WORK SESSION (Open to the Publicj Item 4: The City Council of the City of Coppell met in a work session for the purpose of discussing the City-Wide Storm Water Management Plan. Item 5: Consideration and approval of the City Wide Storm Water Management Plan, prepared by Albert H. Halff and Associates. Acting City Engineer Shohre Daneshman made the presentation to Council. Walter Skipwith and Jean Hansen of Albert Halff Associates were also present to answer questions of Council. Following discussion of this item, Councilman Morton moved to accept the City Wide Storm Water Management Plan as presented and the implementation of the plan as a preliminary guide for Staff to work with. Councilman Nelson seconded the motion. The motion carried 6-0, with Mayor Pro Tem Smothermon, Councilmen Weaver, Morton, Cowman, Robertson and Nelson voting in favor of the motion. There being no further business to come before Council, the meeting was adjourned. 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't:l '" o ~ QJ (;j ci3 D-8 APPENDIX E SUMMARY OF HYDRAULIC DATA r-- 1-3 9~:-3 ZJ Wtr.l1lS ~1-3 ~E-3 1:) Wtr.l1lS 171-3 1E-3 tpUlUg POOMUOllCO 0-3 OE-3 10 Wtr.l1lS Zl-3 LZ-3 J[~1;) UOlU~O n-3 17Z-3 l~Arn hlJUJ.IJ. ~ql JO J[lod UI[3 01-3 1Z-3 90 Wtr.l1lS 6-3 OZ-3 ~O Wtr.l1lS 8-3 61-3 V170 WR~llS L-3 91-3 170 Wtr.l1lS 9-3 ~1-3 EO Wtr.l1lS ~-3 171-3 VZO Wtr.l1lS 17-3 0-3 ZO Wtr.l1lS E-3 n-3 10 Wtr.l1lS Z-3 Z-3 J[~1;) ~UJA~dR10 1-3 'oN ~oRd Wtr.l1lS 'oN ~IqR.L ~{qR.L JO lSJ'l 'z 'SPOOU ;)A!1O:xIs:lJ ;)q1 Aq (l;)l11punll! PUll[ JO 1l;)Jll ;)A!lll[nwn:> ;)q1 S! BaJV ~poo(.!I upB(Dmn:J "XOJddV 'W1l;)J1S ;)q1 JO ;)llllJ01S (;)UUllq:> pUll ,(;)I111A IlU!lSJlQ ;)q1 JO ;)JnSll;)W II S! S!I[J. 'UO!1O;)8 SSOJ:> lSJ!j ;)q1 WOJj ~JnSll;)W W1l;)J1S ;)q1 U! J;)lIlM JO l;);)J-;)J:>1l U! ;)Wn[OA ;)A!lll(nwn:> ;)q1 S! a:huOlS UJlB(Dmn:J 'AtJ:>O[;)A [;)UUllq:> ;)llllJ;)All ;)q1 S! AtJ30(3A '(01-3) ';)[qlll J[JOd Wj3 ;)q1 uo ~pnJ:>lI! <>SIll ;)J1l SUO!lIl,\;)[;) ;):>1lJ.Ins J;)l1lM ddS;)I[J. 'SUO!lll,\;)j;) ;):>IlJlns J;)lIlM p;)lndwoo J1l;)A 001 1il Z ;)ql s:lA!1l 'rnSM:> '(ol-ill ';)jqlll J[JOd Wj3 ;)ql U! p;)pnj:>u! OSjll S! WdS) POOH l:>;)foJd pJllpUlllS ;)I[J. 'pUoo;)s J:xI l;};}J :>Jqn:> U! ;)IlJllq:>SJP p:xIoj;),\;)P AUnJ J1l;)A 001 1il Z ;)ql s:l!J!lU;)P! ~ 'sdllW 1I!1ljd pooU ;)q1 UO pUll j;)pow Z-JtJH ;)q1 1I! ;)WllU UO!l:>;)8 ssw:> ;)q1 SJ1lnb;) QOJl3aS NOI.LdIll:::>s:ilU TI8VIlIV A '~Iqm ~~ql UJ ~UJRlUOO ~{qRJlRA ~ql JO UOnRURIdx~ J~Jlq pUR ~UnSJI R SJ SMOIIOJ lRqM. 'llod~l SJql UJ ~pnpUJ SWtr.l1lS ~ql JO IIR 10J I~POW l~lndwoo Z-;)3H ~ql WOlJ RlRP :JnnRlpAq ~ql JO ~JlRWWnS UJRlUOO ~1-3 q~nOlql 1-3 ~IqR.L ~{qRJlRA JO uonRuRIdxa 'I V.Lva :>nnVlICLUI.!IO AlIVWWilS 3: XUIN3:dcIV TABLE E-! GRAPEVINE CREEK SUMMARY OF HYDRAULIC DATA Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (cfs) ffil !mll (Acre- Ft) (Acres ) 7250.000 5250.00 434.26 4.04 .00 .00 7250.000 18200.00 440.71 6.23 .00 .00 7500.000 5250.00 434.54 3.96 7.53 1.25 7500.000 18200.00 441.02 6.22 16.77 1.57 8000.000 5250.00 435.00 3.82 23.02 3.59 8000.000 18200.00 441.66 5.97 51.05 4.77 A 8500.000 5250.00 435.48 4.56 37.53 5.88 8500.000 18200.00 442.20 6.62 84.33 7.95 9500.000 5250.00 437.18 5.30 62.12 10.28 9500.000 18200.00 443.76 7.13 145.17 14.07 10500.000 5250.00 439.20 4.71 86.29 14.73 10500.000 18200.00 445.52 6.85 204.97 20.31 10850.000 5250.00 439.77 4.57 95.38 16.32 10850.000 18200.00 446.14 6.56 226.80 22.62 10935.000 5350.00 439.89 4.62 97.64 16.70 10935.000 16600.00 446.35 6.22 232.11 23.13 10936.000 5350.00 439.88 4.81 97.66 16.70 10936.000 16600.00 446.33 6.42 232.17 23.14 11044.000 5350.00 440.09 4.71 100.45 17.17 11044.000 16600.00 446.50 6.55 238.52 23.71 11045.000 5350.00 440.13 4.52 100.47 17.18 11045.000 16600.00 446.54 6.46 238.58 23.72 , 11070.000 5350.00 440.16 4.63 101.15 17.29 11070.000 16600.00 446.65 6.11 240.11 23.87 11275.000 5350.00 440.47 4.58 106.61 18.22 11275.000 16600.00 446.89 6.30 252.84 25.19 11276.000 5350.00 440.44 4.82 106.64 18.22 11276.000 16600.00 446.87 6.45 252.90 25.20 11296.000 5350.00 440.48 4.79 107.15 18.32 11296.000 16600.00 446.90 6.44 254.11 25.32 E-2 ~:-3 6L"OTl Z6'6Z9 99'9 8Z'm 00'O~091 000'019~1 178'6L lO'VPZ 66'f ~9'9~v OO'OOZ~ OOO'019~1 89'OTl ff'6Z9 OZ'8 lL"l9V OO'O~091 OOO'OO9~1 18'6L lL"fvZ 66'f f9'9~v OO'OOZ~ 000'009~1 6~'601 vf'ZZ9 90'9 ~6'19v 00'0~091 Ooo'OZ~~l Sf'6L 8~'lvZ 01'9 Z1'9~V OO'OOZ~ ooo'OZSSl 8~'801 fS'L19 89'9 fv'l9V OO'O~091 ooO'OLv~l W'6L 01'OVZ Lf'f 9Z'9~V OO'OOZ~ ooo'OLv~l 9Z'801 08'~19 L6'L 0~'6SV 00'O~091 ooo'OVPSl L6'8L VO'6fZ 8f'f SZ'9~V OO'OOZS ooo'OtvSl 178'~O1 60'VQ9 fZ'6 OZ'6~V 00'O~091 ooO'O~f~l zv'a ZL"vfZ ~6'9 v~'~~v OO'OOZ~ ooo'O~f~l Sl'~8 fZ'vl~ 60'6 ~O'V~V OO'O~091 OOO'OLlvl SZ'19 W'661 SV'9 OL"l~v OO'OOZ~ ooo'OL IN :::> S9'lL 8L"89V O~'L 68'lSv OO'OS09l ooo'OL9fT 9L"lS Z6'081 00'9 06'6VP (X)'OOZS ooo'OL9fT 86'69 lS'm Z~'Ol 80'l~v OO'O~091 ooo'OZ9fT f6'O~ SS'6L 1 179'8 86'M OO'OOZ~ ooo'OZ9fT Of'~v 06'vLf lL"f ~1'O~V 00'00991 OOO'OZ8Z1 9Z'~f lL"vSl 178'v fZ'9VP oo'O~f~ OOO'OZ8Z1 fv'~Z f8'vSZ 80'L 8L"LVP 00'00991 OOO'fTfTl OV'81 6v'Wl 16'f lO'VVP OO'O~f~ ooo'fTfT 1 s: 9f'~Z 6f'vSZ 6v'Tl 6f'gtp 00'00991 ooo'WfT 1 Sf'81 SZ'Wl 18'L OZTVP OO'OSf~ ooo'WfTl vf'SZ Of'v~Z 60'fT 89'~VP 00'00991 ooo'OOfTl ff'81 lZ'Wl 09'6 f9'ZVP OO'OSfS ooo'OOfTl vf'SZ 9Z'VSZ 60'8 ~9'gtp 00'00991 OO()'66ZTl ff'81 OZ'Wl Sf'8 Ov'OVP OO'O~fS OOO'66Z11 ff'SZ 91'VSZ 60'8 S9'9VP 00'00991 000' L6Z11 Zf'81 L1'Wl L9'6 96'6fv OO'OSf~ ooo'L6Z11 ( S:).J:)y ) ( ld -:)J:>Y) ~ UP ~sp) uOH:>:)S ll:)JV :)~llJ01S AlPOl:)A '13SA\:::> {) {Y.)poold :)AHlllnwn:::> :)AHlllnwn:::> 'xOJddy (p.lDUnUO:J) V.LVO ::>nIlVlICLUI .fO AlIVWWIlS )I:i{IDI::> :i{NIMIdVlI~ l-:i{ :i'lHV.L TABLE E-l GRAPEVINE CREEK SUMMARY OF HYDRAUliC DATA (continued) Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (cfs) au @ll ( Acre- Ft) (Acres ) 15630.000 5200.00 456.65 4.26 244.63 79.91 15630.000 16050.00 464.48 6.35 631.47 111.09 15640.000 5200.00 456.68 4.11 244.95 79.95 15640.000 16050.00 464.51 6.24 632.39 111.27 15650.000 5200.00 456.69 4.11 245.28 79.99 15650.000 16050.00 464.52 6.23 633.30 111.45 15660.000 5200.00 456.64 4.81 245.58 80.03 15660.000 16050.00 464.43 7.18 634.18 111.63 15680.000 5200.00 456.74 4.11 246.15 80.10 15680.000 16050.00 464.66 5.41 635.75 111.91 15730.000 5200.00 456.82 4.04 247.61 80.30 15730.000 16050.00 464.77 5.03 639.83 112.56 D 16480.000 5280.00 457.83 4.59 275.11 87.58 16480.000 16250.00 465.44 3.61 737.41 125.19 17600.000 5280.00 459.72 6.69 317.55 104.64 17600.000 16250.00 466.02 5.54 924.42 146.56 17980.000 5280.00 460.89 3.24 333.13 110.47 17980.000 16250.00 466.44 3.96 981.97 153.89 18150.000 5280.00 460.98 5.32 340.63 112.60 18150.000 16250.00 466.51 5.66 1002.41 156.37 18210.000 5280.00 461.06 6.07 342.92 113.33 18210.000 16250.00 466.58 5.97 1009.15 157.25 18240.000 5280.00 460.52 9.42 343.72 113.67 18240.000 16250.00 466.51 7.15 1012.13 157.67 18320.000 5280.00 461.75 6.46 345.66 114.57 18320.000 16250.00 466.72 6.73 1019.64 158.81 18450.000 5280.00 462.08 6.50 349.71 116.11 18450.000 16250.00 466.92 7.05 1032.29 160.77 18500.000 5280.00 462.06 7.12 350.93 116.52 18500.000 16250.00 466.83 8.24 1036.66 161.54 E-4 ~-3 r- ~P.L61 SP"9l.Z1 zrn ~P"8LP 00"00191 ()(Xn 16.Ln SP"gpp mOL L9"ZLP 00"0~1~ (xxn gz"t61 88"0~1 lZ"n 6P"~LP 00"00191 000"0691Z r- 9t"9n Z6.LtP 09"8 6P"OLP 00"0~1~ 000"0691Z 69"061 ~t.LtZl Zt"Zl L~"tLP 00"00191 009. L9"~tl orttp P~"L 61"6917 00"0~1~ 009. P~.981 ~t"60Z1 6L"~ 9L"tLP 00"00191 OO~" ZL"tn P(rozp tz"t tZ"6917 00"0~1~ OO~" W.Z81 8r9L n 69"L L8"ZLP 00"00~91 OOO"OP~OZ 09"Otl n"zOP 9t"P 8L"m OO"O~Z~ OOO"OP~OZ 3 18"LLl 1O.opn ~L"8 18"lLP 00"00~91 OOt" tP.9Z1 Z6"t8t 16"~ 86" L917 OO"O~~ OOt" PL"ZLl Lt"6011 Zt"6 Ot"OLP 00"00~91 OOZ" pcrtZl n.tLt 1~"6 Zt"~917 OO"O~Z~ OOZ" Lt.891 ~rZ801 t9"L 917"6917 00"00~91 oor m.Oll ~8"Wt OP"~ OL "pgp OO"O~Z~ oor ~6.Z91 Z8"9ffil 8t"L 9L"8917 00.0~Z91 000"0~981 It.Ln ~~"P~t 69"8 Z~"Z917 00"08Z~ 000"0~981 6t.Z91 PZ"tPC)l n"~ 6L"m 00"0~91 000"~1981 6O"Lll PL"t~t 89"P ~8"Z917 00"08Z~ 000"~1981 LrZ91 ~9"lPOl zr~ 8L"m 00"0~Z91 000"00981 ~6"9n 9Z"t~t lL"P 18"Z917 o(rogz~ 000"00981 98.191 PZ"6tOl 9~"n 917"99P 00"0~91 000"99~81 tL"9n tt"Z~t 09"~ ~~"Z917 OO"08Z~ 000"99~81 98"191 lZ.6ml ~9"0l 6~"ggp (XrO~91 000"~9~81 tL"9n 1 t"Z~t 9~"~ ~~"Z917 00"08Z~ 000"~9~81 89"191 sp"Lml 01"11 ~"ggp 00"0~Z91 000"~1~81 8~.9n tZ"l~t 69"~ LP"Z917 OO"ogz~ 000.~1~81 89.191 ~p"Lml W"Ol tt"ggp 00"0~Z91 000"Pl~81 8~"9n lZ"l~t 6P"~ 6P"Z917 00"08Z~ 000.Pl~81 ( ~.J:)y) ( H -:).J:)Y) rsaJJ mJ ( sj:) ) uO!l:>:)S WlV :)gB101S AtPOl:)A J:3SA\;) 0 JY.JpooH ~A!lBlnmn;) :)A!lBlnmn;) "XOJddy (p3nOIluo3) V~V(I :JIIDV1ULIII.1l0 AlIVWWilS XiIIDI:J 3:NIMIdVlI~ 1-3: :rulV~ TABLE E-l GRAPEVINE CREEK SUMMARY OF HYDRAUUC DATA (continued) Approx. Cumulative Cumulative Flooded r- Q CWSEL Velocity Storage Area Section (cfs) .au @ll ( Acre- Ft) (Acres ) F 22600.000 5150.00 473.64 7.35 453.46 139.48 22600.000 16100.00 480.03 9.66 1296.75 200.00 2.000 5150.00 475.25 7.62 463.40 141.62 2.000 16100.00 481.16 12.72 1323.84 203.29 23900.000 5150.00 477.63 5.25 477.64 143.96 r- 23900.000 16100.00 484.48 6.60 1364.10 208.13 3.000 5150.00 478.53 4.92 488.82 145.75 3.000 16100.00 485.01 7.55 1392.89 211.25 4.000 5150.00 479.51 6.02 501.47 147.65 4.000 16100.00 485.88 9.01 1422.58 214.67 5.000 5050.00 480.01 5.14 504.53 148.03 5.000 15500.00 486.60 7.85 1430.69 215.83 24930.000 5050.00 480.42 5.18 509.97 148.74 24930.000 15500.00 487.17 7.60 1443.21 217.25 6.000 5050.00 480.39 6.32 511.94 149.00 6.000 15500.00 486.98 9.49 1447.74 217.77 25085.000 5050.00 479.78 11.25 513.12 149.16 25085.000 15500.00 486.48 13.05 1451.04 218.26 25135.000 5050.00 481.04 8.66 513.71 149.25 25135.000 15500.00 487.21 11.87 1453.03 218.66 25185.000 5050.00 481.67 7.08 514.51 149.37 25185.000 15500.00 487.82 11.08 1455.31 219.03 25235.000 5050.00 482.12 5.16 515.56 149.51 25235.000 15500.00 488.33 9.14 1457.81 219.33 G 25280.000 5050.00 482.32 4.06 516.72 149.64 25280.000 15500.00 488.72 7.68 1460.01 219.53 25325.000 5050.00 482.41 3.61 518.09 149.77 25325.000 15500.00 489.02 6.50 1462.40 219.71 25375.000 5050.00 482.45 3.54 519.71 149.93 25375.000 15500.00 489.11 6.31 1465.22 219.92 E-6 L-3 6t'9€Z 9Z'ZLSl €6'9 9€'S6t OO'OSZII OOO'oatLZ t1'9S1 E8'9SS Ot'9 LO'68t OO'OSLE OOO'oatLZ It'ZEZ L9'1SS1 6S'6 16'E6t oo'oszn OOO'OSOLZ t"t'SSI lL'ISS 00'8 8E'L8t OO'OSLE OOO'OSOLZ O€'1 t:Z tL'StSl O6'n ZE'Z6t OO'OSt"t 1 OOO'0889Z Z1'SSI ES'6tS ZZ'L 16'981:' OO'OO8t OOO'0889Z %'8ZZ E8'ZESl Ot'OI €E'16t OO'OSt"t 1 OOO'OSS9Z OE'tSl t1't"tS LS'9 10'981:' OO'OO8t OOO'OSS9Z m'9ZZ OL'tlSl 99'01 LE'06t OO'OSt"tl OOO'OL19Z 66'ZSI ZO'8€S tL'6 18'E8t OO'OO8t OOO'OL19Z €9'ZZZ 81'Z6t 1 SS'L 91'06t OO'OSt"tl OOO'OZ8SZ ZS'ISI SS'ZES E8'8 SV'Z8t OO'OO8t OOO'OZ8SZ 98'IZZ W'L8tl 89'L S9'68t OO'OOSSI OOO'vSLSZ 81'1S1 S1'IES ES'S 99'Z8t OO'OSOS OOO'vSLSZ tS'lZZ E8't8t 1 LS'L IS'68t OO'OO!;!;1 OOO'vlL!;Z PO'lSl OE'OES 9L'!; Z!;"l8t OO'O!;O!; OOO'tlLSZ SZ'IZZ Zv'Z8tl vZ'L Lt'68t OO'OOS!;l OOO'899!;Z 16'O!;1 9Z'6Z!; O9'v LS'Z8t OO'O!;O!; OOO'899!;Z OO'lZZ O6'6Ltl EL'L LZ'68t OO'OO!;!;l OOO'819SZ LL'O!;1 86'LZS 9t'v E!;'Z8t OO'OSO!; OOO'819SZ 6L'OZZ t"t'LLtl lE'L LZ'68t OO'OO!;!;l OOO'89SSZ E9'OS1 W'9ZS 81't ZS'Z8t OO'O!;OS OOO'89SSZ 99'OZZ !;6'SLvl 8E'S t"t'68t OO'OO!;!;l OOO'Ev!;SZ SS'OSl Z8'SZ!; Z1'E L!;'Z8t OO'O!;O!; OOO'Ev!;!;Z !;9'OZZ 68'!;Lvl 6!;'!; 6E'68t OO'OO!;!;l OOO'Zv!;SZ v!;'O!;l 6L'!;ZS SZ'E !;!;'Z8t OO'O!;O!; OOO'ZvS!;Z Z1'OZZ !;1'8917l t"t'!; vE'68t OO'OO!;!;1 OOO'ZZv!;Z 01'O!;1 at'lZ!; orE E!;'Z8t OO'O!;O!; ooo'zzvsz n'ozz 80'89171 !;Z'S 9€'68t OO'OOSSI OOO'lZvSZ 6O'O!;1 LE'lZS L6'Z E!;'Z8t OO'OSOS OOO'lZvSZ ( sg.oy) ( ld -~.oy) "(SiljJ mJ (sp) uO!l:y.)S W.IV ~~hUOlS At!:)OI~A 'l3SM.;) () JY.)POOId ~^!leInwtl;) ~^!leInwn;) 'XOJddy (panullU03) V.LV<I ::>naVlICL\H .110 AlIVWWIlS lI3:IDf::> 3:NIA:ildVlI~ 1-3: :nRV.L TABLE E-1 GRAPEVINE CREEK SUMMARY OF HYDRAULIC DATA (continued) Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (cfs) au !illll (Acre- Ft) (Acres) 27540.000 3750.00 489.50 5.99 558.79 156.39 27540.000 11250.00 495.45 7.88 1580.32 238.36 27570.000 3750.00 489.61 6.07 559.22 156.45 27570.000 11250.00 495.56 8.01 1581.71 238.73 H 27620.000 3750.00 489.59 7.18 559.87 156.53 27620.000 11250.00 495.68 8.87 1584.13 239.38 I 30130.000 3750.00 497.33 7.64 591.13 161.04 30130.000 11250.00 502.60 10.45 1669.45 256.48 30189.000 3750.00 497.65 6.37 591.98 161.18 30189.000 11250.00 502.51 10.92 1671.20 256.73 30190.000 3750.00 497.60 6.95 591.99 161.19 30190.000 11250.00 502.33 12.00 1671.22 256.73 30200.000 3750.00 497.72 6.83 592.12 161.20 30200.000 11250.00 502.79 11.48 1671.44 256.75 30201.000 3750.00 497.90 6.16 592.13 161.21 30201.000 11250.00 503.43 10.03 1671.47 256.76 30250.000 3750.00 498.04 6.85 592.89 161.33 30250.000 11250.00 504.59 8.15 1673.31 257.02 J 31310.000 3750.00 500.74 5.97 610.55 164.07 31310.000 11250.00 506.74 7.15 1719.01 264.61 31480.000 3850.00 501.12 4.90 613.69 164.51 31480.000 11700.00 506.84 8.99 1726.14 265.78 31500.000 3850.00 501.17 4.88 614.05 164.55 31500.000 11700.00 507.04 8.99 1726.74 265.83 31550.000 3850.00 501.26 6.01 614.99 164.68 31550.000 11700.00 508.22 6.22 1729.16 266.21 31750.000 3850.00 501.72 2.39 620.49 165.42 31750.000 11700.00 508.48 3.75 1742.50 267.93 K 32740.000 3850.00 502.13 2.89 653.96 169.93 32740.000 11700.00 508.97 4.05 1810.79 273.67 E-8 6-3 €v'96Z ZS'LOOZ S9'9 L6'ZZS O(rOOL n OOO'08S8€ 08'L81 9L'S€L IS'S 09'81S OO'OS8€ OOO'08S8€ 66'S6Z ZV'VOOZ 117'9 18'ZZS OO'OOL n OOO'OOS8€ Zv'L81 OS'v€L 19'5 S1'81S OO'OS8€ OOO'OOS8€ 9S'S6Z SZ'I00Z 8Z'9 S9'ZZS OO'OOL n OOO'OZ178€ SO'L81 Sv'€€L 91'8 Z8'91S OO'OS8€ OO(rOZ178€ v€'S6Z 179'6661 €Z'9 19'ZZS OO'OOL n OOO'08€8€ 98'981 ZO'€€L €€'8 89'91S OO'OS8€ OOO'08€8€ LS'v6Z LS'v661 L6'11 O€'IZS OO'OOL n OOO'09Z8€ 917'981 99'I€L €S'L lZ'SIS OO'OS8€ OOO'09Z8€ €S'V6Z €€'v661 €L'8 VO'ZZS OO'OOL n OOO'SSZ8€ SV'981 09'I€L IS'L lZ'SIS OO'OS8€ OOO'SSZ8€ 6O'V6Z LS'I661 01'91 SZ'61S OO'OOL n OOO'09€9€ v€'981 Z6'O€L 8€'SI 99'nS OO'OS8€ OOO'09€9€ SZ'€6Z 18'9861 ZZ'SI 66'vlS OO'OOL 11 OOO'OvI9€ LO'981 lO'6ZL LS'L ZL'ns OO'OS8€ OOO'OVI9€ . S9'Z6Z Lv'€861 €€'€J V1'€JS OO'OOL n OOO'OL6S€ OL'S81 SZ'LZL SL'6 08'60S OO'OS8€ OOO'OL6S€ 0L'16Z 99'LL61 LO'L LL'Zl S OO'OOL n OOO'OLLS€ 96'1781 18'vZL 8L'S €V'80S OO'OS8€ OOO'OLLS€ VS'06Z 61'6961 9L'S €v'ZI S OO'OOL n OOO'OLSS€ L6'€81 S6'OZL 6L'€ m'80S OO'OS8€ OOO'OLSS€ '1 S8'6SZ 0L'€961 86'S v1'ZIS OO'OOL n OOO'OSvS€ 8€'€81 €Z'81L 10'17 8L'LOS OO'OS8€ OOO'OSvS€ OS'98Z OV'L€61 L8'S V6'01S OO'OOL n OOO'OL8V€ 1717'081 6O'90L 917'17 8Z'90S OO'OS8€ OOO'OL8V€ LZ'€SZ Is'n61 S€'S m'OIS OO'OOL n ooo'o€€v€ OL'LLl 6S'%9 SL'S 69'ms OO'OS8€ OOO'O€€V€ €S'ISZ S€'S681 SZ'V 178'60S OO'OOL n OOO'SVOV€ LZ'9L 1 €L'069 €v'€ lz'ms OO'OS8€ OOO'SVOV€ ( S~ll:lY ) ~ ld -:ll:lY) "(SOjJ mJ (sp) uO!l:l~S ~~.IV ~~~lolS AtPO(~A 'l3SM.:J 0 lY.)POOId ~^n~(nwn:J ~^n~(nwn:J 'Xolddy (paOO!lU03) v~vo :JnnVllCLUl.!lo AlIVWwns JI3:IDI:J 3:NIMIdVlI~ 1-3: 3:'1av~ TABLE E-l GRAPEVINE CREEK SUMMARY OF HYDRAULIC DATA (continued) Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (cfs) @ !ffill (Acre- Ft) (Acres) 38620.000 3850.00 518.63 5.64 736.39 187.98 38620.000 11700.00 523.02 6.71 2009.03 296.65 38670.000 3850.00 518.95 5.45 737.19 188.22 38670.000 11700.00 523.22 7.45 2010.93 296.92 39720.000 3850.00 523.06 7.76 750.20 193.40 39720.000 11700.00 526.25 7.52 2045.80 304.33 41180.000 2150.00 526.13 2.63 793.59 212.64 41180.000 6150.00 528.57 3.14 2167.93 353.86 41950.000 2150.00 526.91 5.79 813.90 220.76 41950.000 6150.00 529.23 8.04 2219.72 376.59 42050.000 2150.00 526.67 9.21 814.92 221.09 42050.000 6150.00 530.67 9.18 2223.09 378.67 42090.000 2150.00 527.75 6.20 815.21 221.15 42090.000 6150.00 533.84 2.23 2227.25 380.33 42170.000 2150.00 528.36 3.52 816.57 221.53 42170.000 . 6150.00 533.87 1.52 2243.16 384.70 44200.000 2150.00 531.08 5.46 848.49 231.52 44200.000 6150.00 534.12 4.11 2481.01 456.32 45820.000 2650.00 537.09 6.21 869.14 238.71 45820.000 7500.00 538.16 11.43 2547.39 492.09 47450.000 2650.00 541.32 5.52 894.61 251.89 47450.000 7500.00 543.55 5.80 2616.56 526.74 47540.000 2650.00 541.36 5.58 896.01 252.28 47540.000 7500.00 543.60 5.53 2621.25 529.16 47640.000 2650.00 541.85 4.03 897.98 254.04 47640.000 7500.00 543.89 3.73 2630.71 533.77 47670.000 2650.00 543.12 1.95 899.56 255.19 47670.000 7500.00 548.23 1.02 2637.42 535.26 47720.000 2650.00 543.12 2.30 903.09 257.37 47720.000 7500.00 548.24 1.08 2653.78 537.84 48350.000 2650.00 543.33 2.08 929.65 270.18 48350.000 7500.00 548.26 1.74 2783.50 561.67 E-lO n-3 lo9'O~ 08Tl1 lo9'v S~'SOS OO'OSSV OOO'SStv a'v1 V~'ZS 98'Z S~'9OS OO'OOlo1 OOO'SStv Sl"O~ v6'lZl %'6 Zl." LOS OO'OSSV OOO'OOtv 6S'EJ ~Z'lS tv'v SZ'9OS OO'OOlo1 ooo'OOtv 6l."6Z SV'OZl 69'~ OO'SOS OO'OSSV OOO'09~V 99'~1 6~'OS ll."Z Sl"SOS OO'OOlo1 OOO'09~V vs'a SO'n1 v~'~ Zl." LOS OO'OSSV ooo'onv v~'Zl VS'SV SZ'Z 96'VOS OO'OOlo1 ooo'onv 09'ZZ loS'loS loS'Z 6l"LOS OO'OSSV OOO'OSS~ 90'6 a'~~ ~l."1 ~9'VOS 00'OOlo1 OOO'OSS~ 1Z'lZ SS'lS SO'S 9l."9OS OO'OSSV OOO'SZv~ OZ'S 66'6Z ~v'~ S~'VOS OO'OOlo1 OOO'SZV~ Z9'91 66'99 9l."S lo~'VOS OO'OSlS OOO'OO6Z SS'S Slo'a Sl."S 6l."lOS 00'0061 OOO'OO6Z s~'n Zl."SV lol."9 Z6'OOS OO'OSlS OOO'09OZ SS'~ ~9'91 O~'S Zl"lo6v 00'0061 OOO'09OZ 98'lo lo9'v~ OS'9 6Z'S6V OO'OSlS OOO'OZV1 9Z'Z 16'01 lS'v 09'v6v 00'0061 OOO'OZV1 09'v v~'lZ S~'9 Z~'96V OO'OSlS OOO'OZS Sl"l 6l"9 W'9 9l."06v 00'0061 OOO'OZS ZO'l a's Zl"V 6S'S6V OO'OSlS OOO'O~~ 9Z' Sl."l 98'~ V l."SSV 00'0061 OOO'O~~ 19' 60'~ VS'6 LO'v6v OO'OSlS OOO'09Z lol" Sl"l SZ'9 1Z'SSV 00'0061 OOO'09Z ZV' ZO'Z O6'S SO'Z6V OO'OSlS OOO'OlZ vl" ZS' S~'lo Zl."98V 00'0061 OOO'01Z S~' ~S'l Zl."9 vl"Z6v OO'OSlS OOO'OOZ ~l" Sl." OZ'S ~S'98V 00'0061 OOO'OOZ 00' 00' 19'v SS'16V OO'OSlS OOO'OZl 00' 00' 6l"v 9~'98V 00'0061 OOO'OZl ( S~DY) ~ld-~DY) {SOjJ (ijJ ~sp) uO!l:>~S tr.).IV ~~llJOlS AtPoI~A 'l3Sh\;) 0 JY.)poo{d ~^!lgInmn;) ~^!lgInmn;) 'XOJddy V.LVG3nnV1UL\H JlO A.lIVWWilS l~ WVIDI.LS l-:iI :.;rUIY.L TABLE E-2 STREAM Gl SUMMARY OF HYDRAUUC DATA (continued) Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (cfs) .ffil LfiID ( Acre-Ft) (Acres ) 4585.000 1700.00 506.66 1.47 55.25 15.10 4585.000 4850.00 508.92 2.40 129.03 31.95 4840.000 1200.00 507.01 3.35 59.82 16.63 4840.000 3500.00 509.41 4.03 138.60 34.73 5080.000 1200.00 507.56 3.63 62.08 17.66 5080.000 3500.00 509.86 4.21 144.83 37.29 5090.000 1100.00 507.62 3.24 62.18 17.71 5090.000 3300.00 509.91 3.89 145.09 37.41 5115.000 1100.00 510.11 2.03 62.66 17.93 5115.000 3300.00 510.92 4.88 145.92 37.76 5150.000 1100.00 510.15 1.32 63.68 18.36 5150.000 3300.00 511.17 2.72 147.40 38.31 5620.000 1000.00 510.42 2.95 73.26 22.90 5620.000 2900.00 511.89 3.81 163.35 44.32 5990.000 1000.00 511.66 2.90 76.83 25.26 5990.000 2900.00 513.17 3.58 171.64 48.35 E-12 n-3 VZ.S O€"ZZ Z9.€ LCOOS 00"0€6 OOO"SZ€€ zr€ 8V.6 96.€ lS"L6v 00.S9€ OOO"SZ€€ 6O.S €9.1Z S9"€ W"OOS 00"0€6 OOO.01Z€ m.€ ZZ.6 vv"€ 1€"L6v 00"S9€ OOO.01Z€ €9.v OZ.61 08"Z 8V.OOS 00.0€6 OOO.OS8Z 69"Z zr8 8Z"Z 90" L6v 00"S9€ OOO"OS8Z OZ.V 1O"L1 VS"Z 8€.OOS 00"0€6 000.08SZ OV.Z OZ.L 69"Z Z8.96V 00"S9€ 000.08SZ 9S"€ srv1 OZ"€ zroos oo.oon OOO"09ZZ PO"Z 9r9 6€"€ v€"96v OO.OOS OOO"09ZZ VS"Z 'MrD1 gg"€ ZC66V oo.oon 000"0681 1C1 Lrs 9CS 80"S6V OO"OOS 000"0681 9V"Z €9"01 lO"v 89"66v oo.oon 000"S981 69"1 zrs SO"9 v6"v6v OO.OOS 000"S981 9Z.Z 66.6 1O.S W"96V oo"oon 000.0081 19.1 16.v 9rv 6S"€6V OO.OOS 000"0081 'MrI VZ"8 19.v Z9.V6V oo"oon 000"01S1 1€.1 PO.V v€.€ 6O.'l6v OO"OOS OOO.OlSl OS"l S6.9 L€.9 8S.'l6V oo"oon 000.08Z1 n.1 zv.€ 68"S 1O"06v OO"OOS 000.08Z1 6v.1 16"9 8V"6 L€"16v oo.oon 000.OLZ1 or1 n"€ €€"L ZV.68V OO"ooS 000"OLZ1 n.1 VCS 9C9 'l6"m 00"OS91 000"OZD1 S8. 08"Z 98"v vrs8V 00.OS9 OOO"OZ01 60.1 69.S SS.6 6CS8V 00"OS91 000"0101 vg. 8CZ ZCL Oz"m 00.OS9 000.0101 €S. 6r€ L9.€ 0€.€8V 00"OS91 000"OL9 OV. 8S.1 V6.Z 16"6Lv 00"OS9 000"OL9 00. 00" 18"v W.Z8V 00"OS91 OOO"O€€ 00" 00. ZS.€ OS.8Lv 00"OS9 OOO"O€€ (~'oy) ~ ld -:),Oy) "(SOjJ mJ (sp) uO!l:):)S WlV :)~hlJ01S htPOI:)A 'l3SM.:::> 0 lY.)POOH :)A!lllInwOJ :)A!lllInwn:::> "Xolddy V.LVO :::>nIlV1ULUI ~o AlIVWW11S Z~ WVIDLLS [-33'lHV.L TABLE E-4 STREAM G2A SUMMARY OF HYDRAULIC DATA Approx. Cumulative Cumulative Flooded Q CWSEL Velocity* Storage Area Section ( cfs) au Lmll (Acre- Ft) (Acres) 250.000 150.00 486.64 3.09 .00 .00 250.000 350.00 487.99 3.88 .00 .00 700.000 150.00 496.07 6.80 .36 .22 700.000 350.00 497.19 6.94 .73 .37 710.000 150.00 496.98 3.45 .37 .22 710.000 350.00 498.05 3.98 .74 .38 1050.000 150.00 501.04 2.14 .83 .57 1050.000 350.00 501.97 2.73 1.61 .86 E-14 Sl-3 6L"1 ZZ'9 S6'P lZ'f:6P (XrOSf: oo<rOStl S6' 6f:'1 96'f: lZ'Z6P 00'091 ooo'OSPl 8L"1 lZ'9 8f:'L 9t.Z6P OO'OSf: ooo'Ml P6' 6f:'1 8r9 19'16P 00'091 ooo'Ottl W'l 66'S P6'f: ZL"68t OO'OSf: ooo'oon PS' a'l 09'f: Z8'ggp 00'091 ooo'oon n'l SS'S 8S'P f:6'L8t OO'OSf: ooo'OWl S9' to'l SS'f: Z6'm 00'091 ooo'OWl 6f:'1 f:S'S n'L OO'L8t OO'OSf: ooo'OSOl W' ZO'l f:r9 8rm 00'091 ooo'OSOl OZ'l Lrs ZO'P SC08t OO'OSf: 00<rOZ8 OS' f:8' OS'f: 9S'6LP 00'091 000'OZ8 8rl f:rs LP"P PS.Q8t OO'OSf: 000'008 6P' Z8' SO'9 f:8'8LP 00'091 000'008 PS' 8L"f: ZL" 99.Q8t OO'OSf: 000'009 a' IS' ZS'l SZ'9LP 00'091 000'009 6S' PS'Z PL" S9.Q8t OO'OSf: 000'S6P 60' PZ' ZP"l sr9LP 00"091 000'S6P LP' S6'1 69' S9.Q8t OO'OSf: OOO'OSP to. zr f:f:'1 f:r9LP 00'091 OOO'OSP SZ' orl 6S' S9.Q8t OO'OSf: OOO'OOP 10' to. 98'6 9rPLP 00'091 ooo.oot m' or LS'l S9'9LP OO'OSf: OOO'PZf: 10' 10' oo'n f:Cf:LP 00'091 OOO'PZf: 00' 00' ZCL 9S'ZLP OO'OSf: 000'00f: 00' 00' W'9 lL'lLP 00'091 000'00f: (~x>y ) ( ld -:)X>Y) {SOjJ mJ {Sp) UO!l:Y.)S ~.IV :)~eJ01S At!:lOI:)A 'l3SA\:J {) lY.)poo{d ~A!leInmn:J :)A!leInmO;) "XOJddy V.LVCI3nflVlICL\H.!IO AlIVWWflS f~ WVIDI.LS S":>J: :>rIUV.L TABLE E.6 STREAM G4 SUMMARY OF HYDRAUliC DATA . Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (cfs) .au .cmll (Acre- Ft) (Acres ) 300.000 270.00 468.67 3.86 .00 .00 300.000 1000.00 469.78 6.00 .00 .00 500.000 270.00 471.21 4.40 .33 .30 500.000 1000.00 472.99 8.09 .85 .52 540.000 270.00 471.47 5.56 .39 .33 540.000 1000.00 473.39 8.68 .99 .58 560.000 270.00 474.27 10.31 .41 .34 560.000 1000.00 478.45 4.17 1.11 .64 620.000 270.00 475.47 8.50 .45 .35 620.000 1000.00 480.51 2.98 1.97 .96 630.000 270.00 476.89 1.38 .47 .35 630.000 1000.00 480.55 1.06 2.20 1.02 720.000 270.00 476.93 .89 1.01 .50 720.000 1000.00 480.55 1.43 4.11 1.40 r- 1000.000 270.00 476.98 1.40 2.67 1.15 1000.000 1000.00 480.59 1.54 8.81 2.48 1300.000 270.00 477.38 6.30 3.49 1.61 1300.000 1000.00 480.64 4.14 12.06 3.43 1320.000 270.00 478.15 3.60 3.52 1.63 1320.000 1000.00 480.71 4.04 12.19 3.47 1440.000 270.00 479.09 5.01 3.69 1.75 1440.000 1000.00 480.95 7.14 12.76 3.71 1570.000 270.00 480.33 4.13 3.87 1.85 1570.000 1000.00 482.21 7.51 13.19 3.88 1760.000 230.00 481.38 3.85 4.17 2.03 1760.000 830.00 483.71 3.84 14.03 4.21 1900.000 230.00 481.87 3.37 4.42 2.22 1900.000 830.00 483.93 4.21 14.85 4.53 2150.000 230.00 482.69 4.11 4.84 2.58 2150.000 830.00 484.38 4.71 16.17 5.12 E-16 1.1-3 9S"S (I"l€ 'It" 'lS"OOS OO"O€S OOO"Qt8'l 6t"€ 6S"6 tl" n"66t OO"oa OOO"Qt8'l tS"L 69"€'l 'It" ZS"OOS OO.O€S OOO"OOa L6.'l €S.S 1€" n"66t 00"0€'l OOO"OOa 6'l"L 99"'l'l L9.S €S"OOS OO"O€S OOO.OL9'l t6.'l SS.S 19.17 S6"S6t 00"0€'l OOO"OL9'l l'l.L SS"Z'l 6l"L SZ"OOS OO"O€S OOO.Q99'l t6"'l tS.S 19"17 S6.86t OO"oa OOO.Q99'l L9"9 S€.l'l 66" 90" L6t OO.O€S OOO"08SZ U"'l Lt.S SO"6 €S"€6t 00"0€'l OOO"08SZ 9S.9 16"0'l 96" 90" L6t OO"O€S OOO"09SZ 16.'l St"S Ll"€ 'l9"€6t 00"0€'l OOO"09SZ a"9 SS"61 96" 9O"L6t OO"O€S OOO"SOSZ LS"Z 6'l"S SZ"l L9"€6t 00"0€'l OOO"SOSZ 88"S SO"Sl 88"1 to" L6t OO.O€S OOO.Dtt'l IS"'l 'll"S 'lS.9 'lS"Ut 00"0€'l OOO"Qtt'l 'lS"S ZS"Ll €'l"'l to" L6t OO"O€S OOO"8'lt'l lS"'l 'll"S SL"6 tt"16t 00"0€'l OOO"8'lt'l 6S"S SO"Ll 9t.S to"t6t OO.O€S OOO"tL€'l 08"Z 6Q"S LL"6 176"0617 00.0€'l OOO"tL€'l tS.S €6"91 'll"€ SS"€6t OO"O€S OOO.09€'l 6L"'l SO"S LL"6 ts"06t 00"0€'l OOO"09€'l 'lS"S 6S"91 OL"S €'l.06t OO"O€S OOO"tS€'l 6L"'l W.S (I"L U"sst 00"0€'l OOO.tS€'l Lt"S 6L"91 19"5 'l9"68t 00.0€8 OOO"€'l€'l SL "Z SO"S 6L"L SS"98t 00"0€'l OOO"€'l€'l S€"S LS"91 to"S S€"!;8t OO.O€S OOO"O9'l'l 'lL"'l S6"t O€"€ 96.€8t 00"0€'l OOO"09'l'l l€"S OS"91 6€"L W"tst OO"O€S OOO"ot'l'l OL "Z S6.t €6"t €S.€8t 00.0€'l OOO"Dt'l'l {~.oy) (ld-~.oy) (SiIjJ mJ (sp) UO!l:Y.)S w.IV ~~lllOlS htPOI~ A 13SM.;) 0 JY.)pooH ~A!lllInwtl;) , ~A!lllInwtl;) "Xolddy (p3nopuo:.l) v~va ::>IIIlVH<LUI.iO XlIVWWIlS ~ WVIDUS 9-~ ~RV~ TABLE E-6 STREAM G4 SUMMARY OF HYDRAULIC DATA (continued) Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (cfs) au !!ID (Acre-Ft) (Acres ) 3000.000 230.00 499.41 .31 14.67 4.26 3000.000 830.00 500.82 .88 37.09 9.47 3160.000 230.00 499.41 .58 16.90 4.79 3160.000 830.00 500.81 1.49 40.13 10.12 3185.000 230.00 499.41 .80 17.10 4.86 3185.000 830.00 500.81 1.85 40.43 10.20 3255.000 230.00 499.38 2.60 17.41 4.98 3255.000 830.00 500.62 5.99 40.93 10.36 3300.000 230.00 499.42 2.88 17.50 5.02 3300.000 720.00 500.98 4.86 41.10 10.42 3330.000 230.00 499.53 9.08 17.53 5.04 3330.000 720.00 501.91 7.81 41.19 10.45 r- 3390.000 230.00 502.89 4.11 17.59 5.05 3390.000 720.00 505.19 2.58 41.56 10.57 3420.000 230.00 503.21 1.23 17.67 5.07 3420.000 720.00 505.19 2.18 41.84 10.64 3600.000 230.00 503.23 1.70 18.34 5.26 3600.000 720.00 505.21 2.84 43.25 11.04 3900.000 230.00 503.35 2.70 19.10 5.57 3900.000 720.00 505.36 3.82 44.91 11.62 4200.000 230.00 503.73 3.28 19.64 5.82 4200.000 720.00 505.74 4.80 46.12 12.05 4400.000 230.00 504.07 2.82 19.98 5.99 4400.000 720.00 506.22 3.88 46.90 12.29 r- E-18 61-3 a'l 8S"'Z fS"'f L6'P6P OO'OfZ OOO'OZ6 f9' ZO'l Z9'Z P 1'P6P 00'06 OOO'OZ6 S"Z'l S"S"'Z f1'9 PZ'P6P OO'OfZ 000'006 Z9' 10'1 S"O'S" PS"'f6P 00'06 000'006 go'l Pf'Z Z1'P 1S"'68P OO'OfZ OOO'OOL IS"' 06' 1Z'f S"9'ggp 00'06 OOO'OOL f8' 96'1 S"9'l fZ'68P OO'OfZ OOO'OPS" 9f' 9L' S"8'l 88'L8P 00'06 OOO'OPS" 9S"' 8f'l 81'1 1Z'68P OO'OfZ OOO'OOP 61' LP' PC 88' L8P 00'06 OOO'OOP ff' PC 99' 1Z'68P OO'OfZ OOO'Olf 90' Z1' PP' L8'L8P 00'06 OOO'01f 9Z' fS"' S"1'l 1Z'68P OO'OfZ ooo'pgz pcr S"O' fP'8 PP'98P 00'06 OOO't8Z 60' f1' PO'f 80'L8P OO'OfZ OOO'OOZ PO' m' 18'6 96'S"8P 00'06 OOO'OOZ PO' PO' 9P'9 lP'f8P OO'OfZ OOO'OS"l ZO' ZO' ZZ'S" 99'Z8P 00'06 OOO'OS"l 00' 00' 6P'9 OP'Z8P OO'OfZ 000'001 00' 00' ZZ'S" 99'l8P 00'06 000'001 ~~J:>Y) ~ ld -~J:>Y) "(S<JjJ 0fJ ~sJ:>) uon:>~s wJV ~~-eJOlS AtPOI~A '13SM.;) 0 ~poOH ~^!l-eInwn;) ~^n-eInwO;) 'XOJddy V.Lva :JnnVlICLUI .tIO ..\lIVWwns Vt~ wv:nI.LS L -3 3'UIV.L TABLE E-8 STREAM G5 SUMMARY OF HYDRAUUC DATA Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (cfs) au !!ro ( Acre- Ft) (Acres ) 65.000 55.00 460.61 4.79 .00 .00 65.000 240.00 461.97 6.93 .00 .00 300.000 55.00 463.42 3.76 .07 .08 300.000 240.00 464.86 5.22 .22 .13 400.000 50.00 464.44 6.28 .10 .10 400.000 220.00 466.51 6.35 .34 .24 405.000 50.00 464.68 8.93 .10 .10 405.000 220.00 466.54 7.25 .34 .24 470.000 50.00 466.26 8.95 .11 .11 470.000 220.00 468.45 6.31 .43 .36 490.000 50.00 467.63 1.57 .11 .12 490.000 220.00 468.74 3.14 .46 .41 675.000 50.00 467.89 1.09 .28 .23 675.000 220.00 469.40 1.79 .92 .74 820.000 45.00 470.17 4.36 .38 .32 820.000 170.00 470.97 5.61 1.17 .90 940.000 45.00 473.12 1.94 .42 .39 940.000 170.00 474.24 2.87 1.30 1.01 1050.000 45.00 476.84 4.62 .46 .44 1050.000 170.00 477.66 5.32 1.41 1.10 1080.000 45.00 479.92 10.80 .47 .44 1080.000 170.00 484.17 7.33 1.45 1.16 1120.000 45.00 481.19 10.00 .47 .45 1120.000 170.00 484.63 3.81 1.54 1.28 1130.000 45.00 482.89 1.13 .48 .45 1130.000 170.00 484.69 1.14 1.58 1.32 1300.000 35.00 482.91 .21 .87 .58 1300.000 90.00 484.71 .32 2.46 1.82 1520.000 35.00 482.90 1.34 1.35 .80 1520.000 90.00 484.71 .96 3.43 2.15 E-20 lZ-3 f:1"9 6Z"11 6Z"P OL:ILP OO"()()ZI 000'S8L 1 P1"P 88"P SP'P gz"OLP OO'OSS 000"S8L 1 80"9 61"11 Pf:'P 99'ILP OO"OOZI OOO"SLL 1 I1"P 178"P SO"S Z1"OL P oo"OSS OOO"SLL 1 99.S P1"OI S8"f: SP"ILP OO"OOll 000'SL91 8L:f: n"p 66"f: lL:69P OO"OSS 000"SL91 a"s m"6 6L:f: SZ'ILP OO'ooZI OOO"OLSl 6P'f: 06"f: 9P.f: PP'69P OO"OSS OOO.OLSl 16.P 86.L gz"P oo"ILP oo"ooZI OOO"S9Pl gz'f: ZP'f: S8'f: 11"69P OO"OSS OOO'S9Pl O9"P 11"L P1"S 99"OLP OO"ooZI 000"S9tl Z1"f: LO"f: 9f:"S Zs"m OO'OSS OOO"S9tl LP'P f:L:9 Of:'S LP"OLP OO"OOZI oo<rSltl PO.f: Z6"Z If:"S lZ"m OO"OSS OOO'SIf:l Pf:.P 9f:"9 nos 9Z"OLP OO"ooZI OOO"S9Z1 86.Z LL:Z Of:"S 88" L9P OO"OSS 000'S9Z1 ZZ'P PO'9 66"S S8"69P oo"ooZI OOO.SIZI f:6'Z S9"Z gz'8 8P"m OO"OSS OOO"SIZI S1"P S8"S Sf:"P L8'69P oo'ooZI 000"S811 O6'Z 8S'Z ZO"P L9'm OO"OSS 000'S811 11.P ZL:S 18"01 8Z"m oo"ooll 000"S911 68"Z PS"Z PZ"6 PZ'S9P OO"OSS 000.S911 L6'f: 81"S PS'f: f:9"m OO"OOZI 000"0011 88"Z 9P'Z 11'ZI 6Z"WP OO"OSS 000"0011 16'f: [6"P 91"S 6f:"S9P oo"OOZI 000'0801 L8'Z f:P'Z Z6"S 9S"WP oo"OSS 000"0801 IS.f: 6Z'P Zf:"9 lL:WP oo"OStl 000'0001 W'Z 61"Z OZ.S S6"f:9P 00"009 000.0001 00. 00" 19"Z LO'LSP OO'OStl 000'009 00. 00' 01"Z PP"9SP 00"009 000"009 ( ~J:)V) nd-~J:)V) (S<ijJ mJ ~sp) UO!l:Y.>S ~.IV ~~eJ01S AlPol~A 'l3SM.J {) {Y.}pooH ~^!lelnmnJ ~^!lelnmnJ "XOJddv V.Lva JrIllVllCLUlJlO AlIVWWilS ~ WVIDI.LS 6-3: :fiHV.L TABLE E-9 STREAM G6 SUMMARY OF HYDRAUliC DATA (continued) Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (cfs) @ @ll (Acre- Ft) (Acres ) 1865.000 550.00 470.65 7.11 5.14 4.36 1865.000 1200.00 471.80 8.41 11.89 6.44 1875.000 550.00 471.25 5.14 5.17 4.38 1875.000 1200.00 472.47 6.02 11.96 6.48 1955.000 550.00 471.77 6.53 5.39 4.54 1955.000 1200.00 472.85 8.70 12.43 6.75 2030.000 550.00 472.65 6.63 5.56 4.64 2030.000 1200.00 473.85 8.79 12.76 6.93 2135.000 550.00 473.85 4.77 5.86 4.81 2135.000 1200.00 475.41 5.45 13.38 7.22 2220.000 550.00 474.29 4.66 6.16 5.00 2220.000 1200.00 475.78 5.14 14.05 7.51 2310.000 375.00 474.81 2.82 6.50 5.21 2310.000 850.00 476.22 3.42 14.77 7.80 2620.000 375.00 475.32 2.47 7.76 5.85 2620.000 850.00 476.74 3.59 17.06 8.63 2700.000 375.00 475.35 6.09 7.98 5.95 2700.000 850.00 476.73 7.40 17.44 8.76 2710.000 375.00 475.75 4.95 7.99 5.96 2710.000 850.00 477.10 6.47 17.47 8.77 2775.000 375.00 476.92 7.61 8.09 6.01 2775.000 850.00 478.31 9.27 17.66 8.85 ., 2785.000 375.00 477.72 5.16 8.10 6.02 2785.000 850.00 479.32 6.57 17.68 8.86 2860.000 375.00 478.66 8.37 8.21 6.06 2860.000 850.00 480.30 9.95 17.89 8.94 2870.000 375.00 479.62 5.57 8.22 6.07 2870.000 850.00 481.50 6.94 17.91 8.95 2925.000 375.00 480.57 8.95 8.29 6.10 2925.000 850.00 482.56 10.38 18.06 9.01 E-22 f(;-3 ' w.n L!;.vZ S6.S lS.1O!; O<fOO9 OO<f09Lv ~WL 6v.ot 09.!; ZCOO!; OO.O!;Z OOO.09Lv L€.ll oo.vz vrg 89.00!; 00.009 OOO.08tt a.L LrOl lCv !;!;.66v OO.O!;Z OOO.08tt so.n zv.€z ~.L !;9.S6V 00.009 OOO.OOZV W.L 98.6 OS.!; 0!;.L6v OO.O~ OOO.OOZV €S.Ol 88.ZZ LV.9 06'96v 00.009 OOO.!;€6€ 88.9 S!;.6 Z6.v SC!;6v OO.O!;Z OOO.!;€6€ ZS.Ol 98'ZZ W.S €V.96V 00'009 OOO'!;Z6€ LS.9 L!;.6 V!;'g st'!;6V OO'O!;Z OOO'!;Z6€ grot 1O'lZ a'l €9'96v OO'OOg OOO'OL9€ L!;.9 !;Z'6 Zg'€ 9€'Z6V OO.O~ OOO'OL9€ zrot 6S'OZ OV"l Z9'96V 00'009 00<r199€ g!;'g VZ'6 ZO'!; W'Z6v OO'O~ OOO'l99€ n.Ol 88'OZ !;rl Z9'96V 00'009 OO<f099€ g!;'g vZ'6 ZCZ 69'06v OO'O~ OOO'099€ 90'01 Zg'OZ ZZ'Z 19"96v 00'009 OOO'!;W€ !;!;'g ZZ.6 VZ.6 n'68t OO'O!;Z OOO'!;W€ 06'6 !;6'61 €!;.6 9O'16v OO"OOg OOO'!;S!;€ v!;.g sr6 €€'6 SO'68t OO'O!;Z OOO'!;S!;€ LS.6 06"61 l€.L 1!;'06V 00'009 OOO'OL!;€ €!;.g Lr6 Z!;'!; ~'68t OO'O!;Z OOO'OL!;€ 6!;.6 LV'61 €6'!; L6'L8t OO'OOg OOO'06€€ Zv'g 96'S ZCV lcm OO'O!;Z OOO'06€€ €v'6 zr61 vcv SZ'L8t 00.009 ooo'oa€ Z€'g OS'S VC€ 1 C!;8t OO'O!;Z ooo'oa€ SZ.6 !;CSl OV'L SC!;8t OO'O!;S OOO'O!;l€ €'l'g Zg's !;C!; €z.tst OO'!;L€ OOO'O!;l € !;r6 ZV.Sl a'L €ctst OO'O!;S OOO'OW€ grg !;v's SL'!; 06'Z8t OO'!;L€ ooo.Oto€ ZO.6 6O.S1 OO'L €6.€8t OO'O!;S OOO'!;€6Z org O€'S €rg 19'18t OO'!;L€ OOO'!;€6Z (s~U::lV) lH -:U::lV) "(SOjJ mJ lSJ::l) UO!l::Y.}S ~:}.IV :}~~lOlS htpoI:)A 'l3SM.;) 0 pgPOOH :)A!l~lnWn;) :)A!l~lnwn;) "XOJddv (panu!lUO:l) V.LVO ::>nnVlIOAH.!IO AlIVWwns 9D WVIDI.LS 6-3: WUIV.L TABLE E-1O ELM FORK OF THE TRINIlY RIVER SUMMARY OF HYDRAUUC DATA Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (cfs) @ ffi!ll (Acre-Pt) (Acres ) 77490.000 14200.00 432.99 1.36 .00 .00 77490.000 49800.00 438.77 1.97 .00 .00 77490.000 93100.00 444.49 1.97 .00 .00 80970.000 14200.00 433.34 1.71 443.64 62.34 80970.000 49800.00 439.20 2.30 1222.84 149.94 80970.000 93100.00 444.78 2.17 2073.59 151.35 83400.000 11900.00 433.64 .92 859.22 105.98 83400.000 49500.00 439.59 1.52 2624.81 346.00 . 83400.000 91500.00 445.05 1.56 4562.15 349.21 84750.000 11900.00 433.73 .87 1132.72 136.99 84750.000 49500.00 439.77 1.52 3461.51 471.31 84750.000 91500.00 445.18 1.62 6082.88 475.41 85000.000 11900.00 433.73 1.44 1178.39 142.77 85000.000 49500.00 439.81 2.21 3603.83 495.83 85000.000 91500.00 445.22 2.04 6358.32 500.07 A 86560.000 11900.00 433.89 1.00 1426.88 176.70 86560.000 49500.00 440.03 1.67 4252.10 588.89 86560.000 91500.00 445.36 1.89 7507.87 593.53 87530.000 12600.00 433.87 4.25 1599.07 201.81 87530.000 55000.00 440.09 5.87 4707.17 648.19 87530.000 100000.00 445.43 5.03 8295.97 666.19 87800.000 12600.00 434.08 3.65 1622.07 205.00 87800.000 55000.00 440.18 7.39 4776.69 658.41 87800.000 100000.00 445.42 7.03 8423.26 679.08 87869.000 12600.00 434.13 3.74 1628.08 205.76 87869.000 55000.00 440.28 8.37 4792.15 660.41 87869.000 100000.00 445.44 9.17 8450.61 681.79 87870.000 12600.00 434.13 3.82 1628.17 205.77 87870.000 55000.00 440.28 8.37 4792.35 660.43 87870.000 100000.00 445.38 10.57 8450.92 681.83 87960.000 12600.00 434.26 3.77 1635.79 206.82 87960.000 55000.00 440.87 7.88 4810.18 662.23 87960.000 100000.00 446.74 10.37 8476.70 685.44 E-24 ~-3 ' LC89Pl SP"ZP691 €Z"€ 6P"OSP 00"000001 000"OZ9€6 917" L6€l 91"L806 lCP Q9"SVi:' OO"OOOSS 000"OZ9€6 P€"S€P P6"98ZZ L€"P P€"6€P 00"OO9Z1 000"OZ9€6 L9"P601 S€"S~€l Z6"1 6O"OSP 00"000001 000"00€Z6 6C€POl PCP~L €1"Z ZS"m OO"OOOSS 000"00€Z6 01"n€ ocsnz 6€"Z OP"S€P 00"OO9Z1 000"00€Z6 P6"Z901 PS"€6SZ1 S6"1 SO"OSP 00"000001 000"060Z6 cr"€IOl 6€"6S0L Z€"Z pcm OO"OOOSS 000"060Z6 SZ"L6Z LS"PSOZ lZ"Z O€"S€P 00"OO9Z1 000"060Z6 :> €6"SU OS"ZZ€11 €P"Z IS"6Vi:' 00"000001 000"08806 9Z"Z88 €S"SIZ9 LL"Z SZ"m OO"OOOSS 000"08806 LS"9~ 96"OZ61 ZS"Z LS"L€P 00"OO9Z1 000"08806 16"Z98 ZC€Z901 ZC€ OS"6Vi:' 00"000001 000"00006 98"aS €S"P98S OZ"S 6P"tVi:' OO'OOOSS 000"00006 S€"ZPZ ZC6tSl mop 9P"9tP 00"OO9Z1 000"00006 s: ZP"ZLL ZCS6S6 SO"Z Pt"6Vi:' 00"000001 OOO"OS06S S1"SPL 6t"ILtS W"Z W"tVi:' OO"OOOSS OOO"OS06S pcaz SC1SLl PO"t St"StP 00"OO9Z1 OOO"OS06S LS"€69 It"9LSS S6"S 1 CM 00"000001 OOO"OSI88 66"699 S9"LSSP LC9 OS"1 Vi:' OO"OOOSS OOO"OSI88 SO"60Z IP"ZS91 S9"t 6P"PtP 00"OO9Z1 OOO"OSI88 16"889 tC91SS LCL n "M 00"000001 OOO"OS088 91"S99 ZP"6ZSP W"S lZ"1 Vi:' OO"OOOSS OOO"OS088 €6"WZ U'€Wl 06"€ St"PtP 00"OO9Z1 OOO"OS088 P1"889 9O"SOSS LCL OO"M 00"000001 OOO"Ot088 . Vi:'"m L6"PZSP P1"S tl"l Vi:' OO"OOOSS OOO"Om88 OCWZ 99"11791 16"t 9t"PtP 00"OO9Z1 OOO"Om88 10" L89 6S"P6PS S6"9 96"LVi:' 00"000001 000"00088 St"t99 tS'SISP 91"S 00"1 Vi:' OO"OOOSS 000'00088 €€" WZ S1"6€91 S1"P SZ"PtP 00"OO9Z1 000"00088 SP"S89 W"LLPS 91"L OS"LVi:' 00"000001 000" 196LS ~"Z99 St"OlSP 88"L 88"M OO"OOOSS OOO"I96LS PS"90Z LS"St91 69"€ a"P€p 00"OO9Z1 000"196LS ~~J:>Y) ( ld -gJJY) "(ScJjJ mJ ~ SJ:> ) UO!l:>gs lr.)JV ggeJ01S AlPOIgA '13Sh\:> 0 JY.)pooH :}A!leInwn:> :}A!leInwOJ "XOJddy (panunuoo) Vl.VO ::>nllV1ULUI .110 AlIVWWllS lI:>1AIlI A.l.INnIl. 3Rt .110 )nIO.1l WI3: 01-3: :;rUlVl. TABLE E-IO ELM FORK OF THE TRINITY RIVER SUMMARY OF HYDRAULIC DATA (continued) Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (efs) @ !!'P.ll ( Acre- Ft) (Acres) 93670.000 12600.00 439.60 8.69 2289.79 439.35 93670.000 55000.00 445.70 3.59 9118.96 1405.65 93670.000 10??oo.00 450.51 2.59 17015.79 1477.57 93730.000 12600.00 440.84 3.91 2293.26 440.38 93730.000 55000.00 445.78 3.90 9150.32 1414.91 93730.000 10??oo.00 450.54 1.72 17098.47 1489.18 93760.000 12600.00 440.89 3.88 2295.61 440.70 93760.000 55000.00 445.89 3.72 9163.19 1419.36 93760.000 10??oo.00 450.55 1.72 17137.78 1495.51 93810.000 12600.00 441.06 3.17 2301.27. 442.70 93810.000 55000.00 446.02 3.60 9194.24 1428.26 93810.000 10??oo.00 450.59 2.59 17215.40 1506.49 97570.000 12600.00 442.22 1.98 2902.43 689.13 97570.000 55000.00 446.78 2.29 11374.26 1856.46 97570.000 10??oo.00 450.94 2.10 21324.55 1963.25 98450.000 12600.00 442.46 3.05 3126.93 800.78 98450.000 55000.00 446.97 2.75 12277.23 2026.89 98450.000 10??oo.00 451.05 2.33 22936.60 2136.51 D 99280.000 12600.00 442.91 2.78 3303.98 892.27 99280.000 55000.00 447.23 2.80 13090.46 2189.53 99280.000 10??oo.00 451.19 2.48 24411.00 2301.58 100040.000 12600.00 443.31 2.39 3497.98 989.51 100040.000 55000.00 447.52 2.67 13881.77 2345.25 100040.000 10??oo.00 451.35 2.46 25812.47 2458.61 Note: Information shown on Table E-lO is for the 2-year, 100-year and the Standard Project Flood (SPF), respectively, for a fully developed watershed. E-26 LZ-3 H7'60€ €L."lS61 68't 18'9St OO'89tZZ OOO'OLSO€ S8't81 tZ'SHl 8L'€ Z6'lSt OO'OL8L OOO'OLSO€ 6l'(J6Z lZ'8081 Zl't 9t'9St OO'89tZZ OOO'0196Z 08'691 S€'tSOl 8l'€ Z9'lSt oo'OL8L OOO'0196Z ;) H7'Z9Z SL'SS91 tL'€ lZ'9St OO'89tZZ OOO'OL88Z t9'091 LZ'HOl ZS'€ Z€'lSt oo'OL8L OOO'OL88Z S€'l€Z 66'81S1 L9'S ZS'SSt OO'89tZZ OOO'0808Z l€'LSl L6'6L6 ZS'€ W'lSt oo'OL8L OOO'0808Z 6€'SOZ lS'OSH Sl'€ L€'SSt OO'89tZZ OOO'O€89Z W'Stl 6Z'OO6 SZ'Z 96'OSt oo'OL8L OOO'O€89Z g r-- SO'881 98'6811 9L'S sS'tSt OO'89tZZ OOO'OLLSZ 9O'ZH 91'908 ZL'Z tL'OSt OO'OL8L OOO'OLLSZ Lt'981 H7'OL H 8l'L 9O'tSt OO'89tZZ OOO'O€SSZ 8L'0€1 lL'16L S€'€ Z9'OSt oo'OL8L OOO'O€SSZ t9'6L 1 €€'90H 9O't t6'€St OO'89tZZ OOO'OOLtZ €€'9Zl €S'9tL Z8'l SS'OSt OO'OL8L OOO'ooLtZ Y 6L'€91 69'SL6 L9'Z 88'€St OO'89tZZ OOO'OOH7Z t6'911 tl'9S9 t€'l €S'ost OO'OL8L OOO'OOH7Z 66'€Sl 86'L06 69'Z 8€'€St OO'€80€Z OOO'OO8€Z 86'Hl 6€'O19 09'1 €t'OSt OO'Z€tL OOO'OO8€Z W'9H 8l'8LL t6't 06'ZSt OO'€80€Z OOO'OL€ZZ 80'ml ZO'tlS Z6'l S€'OSt oo'Z€tL OOO'OL€ZZ ZL'9Z1 18'989 lS't L9'ZSt OO'€80€Z OOO'09S1Z Lt'L6 SS'8€t lL'l l€'OSt OO'Z€tL OOO'09S1Z 9€'88 W'€€t 90'€ lS'ZSt OO'€80€Z OOO'O€661 Z6'OL O8'tSZ O€'l LZ'OSt OO'Z€tL OOO'O€661 SZ'6t 9S'LIZ 1O'Z 1 S'ZSt OO'€80€Z OOO'O€€61 6L'8€ €L'8H 86' LZ'OSt oo'Z€tL OOO'O€€61 00' 00' 98'Z 8€'ZSt OO'€80€Z OOO'0tt81 00' 00' 9t'Z 6l'OSt oo'Z€tL OOO'0tt81 ~~l:>Y) ~ld-;)l:>Y) {SiIjJ mJ ~sp) Uon~s ~lV ~~elolS AtPOI~A 'l3SM.;) {) JY.}poo{d ~A!lelnm1l;) ~A!leInm1l;) 'xolddy VJ.VG 3nnV1UUH .i0 AlIVWWns 1I3IDI3 NOJ.N3G n-3 3'18VJ. TABLE E-11 DENTON CREEK SUMMARY OF HYDRAUUC DATA (continued) Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (cfs) au !mll ( Acre-Pt) (Acres ) 31230.000 7870.00 452.20 4.08 1148.11 191.08 31230.000 22468.00 457.02 7.02 2024.24 320.64 32150.000 7870.00 452.58 6.06 1182.25 194.64 32150.000 22468.00 457.64 11.63 2084.50 330.56 32200.000 7870.00 452.39 8.38 1183.55 194.77 32200.000 22468.00 457.31 14.08 2086.70 330.83 32230.000 7870.00 452.48 8.28 1184.66 194.90 32230.000 22468.00 457.86 13.35 2088.63 331.02 32305.000 7870.00 452.15 14.23 1185.63 195.04 32305.000 22468.00 458.20 16.07 2090.78 331.30 32725.000 7870.00 456.94 4.50 1200.21 198.32 32725.000 22468.00 463.25 3.83 2141.30 339.88 33145.000 5645.00 457.47 2.42 1222.79 202.36 33145.000 16681.00 463.50 3.20 2203.27 349.59 33470.000 5645.00 457.61 3.16 1238.16 204.58 33470.000 16681.00 463.71 3.43 2245.48 356.51 34260.000 5645.00 458.06 2.18 1277.89 210.43 34260.000 16681.00 464.11 2.90 2343.93 370.03 34850.000 5645.00 458.30 4.92 1303.22 213.92 34850.000 16681.00 464.38 6.21 2408.50 380.86 34950.000 5645.00 458.43 4.86 1305.87 214.19 34950.000 16681.00 464.60 6.00 2417.65 382.98 D 36970.000 5645.00 460.80 5.30 1357.71 219.91 36970.000 16681.00 467.33 5.83 2618.39 431.74 38200.000 5645.00 461.78 2.44 1409.14 229.55 38200.000 16681.00 468.11 2.48 2799.28 464.08 39290.000 5645.00 462.09 2.84 1481.79 246.05 39290.000 16681.00 468.31 2.98 3025.44 493.82 39440.000 5645.00 461.99 4.81 1490.73 248.14 39440.000 16681.00 468.16 6.05 3058.04 498.94 E-28 6Z-3 LS'O~S 61' L68t L~'~ L'l'9L'p OO'101Z1 OOO'Q'p69~ ~L'O[[ 'pZ''p'pOZ 96'Z 69'89t> oo'ooL'l OOO'Q'p69~ 6L''pZS l'p'S6L'p 9L'9 Q8''pL'p OO'101Z1 OOO'Q6~~~ 66'L'l[ ZZ'91OZ ZZ'[ Z1'89t> oo'ooL'l OOO'Q6~~~ oo'f18L 8'l'6Z9f1 ~[''p ZL'[L 'p 00' 1 'lL n OOO'O~[[~ 'p~'IZ[ OZ'6'p61 L6'1 9L'L9f1 oo'991[ OOO'O~[[~ 6L'9f1 L 09THot 00'[ 66''lL'p 00' 1 'lL n OOO'O~[l ~ ~'~1[ L,'p''pLSl 6O'Z 6'p'L9f1 oo'991[ OOO'O~[l~ 99'9f19 'pZ''p 16[ IS'Z S6'IL'p oo'L[SOI OOO'OOO8t [L'88'l [S'9f1Ll 'p'p'Z 16'm OO''P66Z OOO'OOO8t 'p 1'[Z~ 'p~'~SI[ 8'l'9 L1'69f1 00'18991 OOO'O~9Of1 9Z'1 ~Z L'l''pZ~1 oo'~ Z1'[9f1 OO'~W~ OOO'O~9Q'p lL'oo~ [6'89Q[ ~9'~ 'p[.89t> 00'18991 OOO'Q'p~6[ 6'p'8tZ 61''p6'p 1 'pL''p ~1'Z9f1 OO'~W~ OOO'Q'p~6[ ZS'66'p 'p'p'[9Q[ OZ''p L[.89t> 00'18991 OOO'Q6'p6[ Z['8tZ 9f1''16'p 1 W'[ 9Z'Z9f1 OO'~W~ OOO'Q6'p6[ ~~J:)Y) ~ ld -~J:)Y) (SOjJ mJ ~SP) uO!l:Y.}S w.IV ~~hUOlS AlPOl~A 'l3SM.J 0 JY.}pooH ~^!lglnmnJ ~^!lglnmnJ "XOJddy (~n1l!lOO;)) V.LVU 3nnVlICLUI ..IJ:O A.lIVWWnS }J3:IDI3 NO.LN3:U n-3: 3:'UIV.L TABLE E-12 STREAM Dl SUMMARY OF HYDRAUUC DATA Approx. Cumulative Cumulative Flooded Q CWSEL Velocity* Storage Area Section (cfs) au .cmll ( Acre-Ft) (Acres) 1615.000 370.00 460.19 3.20 .00 .00 1615.000 1600.00 461.91 5.15 .00 ;00 2112.000 370.00 463.59 4.37 1.14 .89 2112.000 1600.00 465.50 7.13 3.05 1.23 2525.000 330.00 470.76 5.58 1.82 1.46 2525.000 1500.00 472.41 7.36 5.12 2.37 2819.000 330.00 474.01 2.86 2.41 2.22 2819.000 1500.00 475.19 4.50 6.97 3.64 3210.000 330.00 476.75 5.99 3.53 3.92 3210.000 1500.00 477.75 6.85 10.38 6.20 3250.000 330.00 480.55 .47 4.57 4.40 3250.000 1500.00 481.09 1.70 11.76 6.75 3500.000 330.00 480.55 .13 19.29 9.81 3500.000 1500.00 481.10 .48 29.46 12.15 3920.000 500.00 480.55 .55 38.63 17.43 3920.000 1300.00 481.12 1.11 53.17 20.09 4200.000 500.00 480.67 4.83 42.21 19.55 4200.000 1300.00 481.32 5.75 58.15 22.69 E-30 H:-3 6S'69 SI"%Z f6'1 9S"'fSV O<rDS"ZS OOO'06S"6 19'LS" 09'lfl s"17'Z fS'9L17 OO'OS"LZ OOO'06S"6 fZ'69 LI"16Z 9f'Zl 617'OSV OO'OS"ZS 000'9ZS"6 L l'LS" OZ'Ofl 66'S lZ'S"L17 OO'OS"LZ 000'9ZS"6 LI"69 fL '06Z f17'S"l 6S"'SL17 OO'OS"ZS 000'176176 fl'LS" S6'6Z1 ZL"6 fS'17L17 OO'Os"LZ 000'176176 lL"89 ZS'SSZ 1717' S" fL" LL 17 OO'OS"ZS OOO'Of176 LL"9S" 9I"6Z1 0I"17 9Z'S"L17 OO'OS"LZ OOO'Of176 L6'617 6S"'ZZZ SV'S" O17'fL17 OO'OILS OOO'OOOS OS"'Z17 S"S"'001 ZS"'17 Sf'lL17 OO'0I6Z 000'0008 ZL"lf 8'(;'ZS"l PS'f fZ'lL17 OO'06fS OOO'S"999 ZO'LZ S"S'L9 Zf'f 68'8917 OO'066Z 000'S"999 s: 617'Zl S"L"99 f9'17 If'6917 OO'06f8 000'0S"1S" 17L"6 W'6Z 17f'17 If'99j7 OO'066Z OOO'OS"lS" Y n's Z17'S"17 6S"'9 8'(;'8917 OO'06fS OOO'fS"L17 60'9 09'81 OZ'17 ZS"'S"917 OO'066Z OOO'fS"L17 m'S" lL'LZ ZL"OI S"S'S"917 OO'06fS OOO'SfZ17 06'Z 1717'6 90'6 Sf'f917 OO'066Z OOO'SfZ17 U'Z If'S"l 6Z'S ZI"17917 OO'06fS OOO'176Lf 8I"1 LI"S" SS"'6 PS'SS"17 OO'066Z OOO'176Lf f6'l fS"'Zl LI"S S"S'f917 OO'06fS 000'1769f L6' 0€'17 L9'9 SO'6S"17 OO'066Z OOO'1769f 19'1 LI"OI Zf'6 ff'f917 OO'06fS 000'176s"f S"L" LZ'f 17L'9 f6'SS"17 OO'066Z 000'176s"f 117'1 17L"S 9f'S 117'f917 OO'06fS OOO'lfS"f 19' W'Z S6'9 lL"SS"17 OO'066Z OOO'lfS"f 8'(;'1 ZS'L 99'8 ZZ'f917 00'06f8 000'17617f fS"' 17f'Z f17'Ol Zf'LS"17 OO'066Z 000'17617f 00' 00' fS'f S"Z'f917 OO'8917ZZ OOO's"zLZf 00' 00' 0S"'17 176'9S"17 OO'OLSL OOO'S"ZLZf ( ~J:)Y) ( ld -~J:)Y) "(SUjJ mJ ~sP) uO!l;)~S W.IV ~gglOlS AlPOI~A 13Sh\:J () Jr.}pooId ~^!lgInwtl;) ~^!lgInwn:J 'Xolddy V.Lva :JnnV1UL\H.!IO XlIVWWIlS H:JNV1UI aOOMNOllO:J (1-:>1 :>I'IHV.L TABLE E-13 COTTONWOOD BRANCH SUMMARY OF HYDRAUUC DATA (continued) Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (cfs) @ ~ (Acre- Ft) (Acres ) 10120.000 2750.00 477.48 12.53 142.57 61.09 10120.000 8250.00 482.83 10.62 339.01 76.74 10130.000 2750.00 478.63 10.04 142.62 61.10 10130.000 8250.00 483.28 9.52 339.25 76.82 10210.000 2750.00 479.85 9.34 143.17 61.26 10210.000 8250.00 483.95 10.17 341.57 77.48 10470.000 2750.00 482.06 4.71 146.04 62.08 10470.000 8250.00 485.53 6.82 349.60 79.39 10655.000 2750.00 482.45 5.69 148.77 62.98 10655.000 8250.00 486.03 7.41 355.83 80.47 10830.000 2750.00 482.99 6.98 150.84 63.74 10830.000 8250.00 486.51 8.64 361.27 81.57 11030.000 2750.00 484.04 4.84 153.47 64.53 11030.000 8250.00 487.57 6.41 367.55 82.84 C 11230.000 2750.00 484.45 2.92 157.62 65.54 11230.000 8250.00 488.08 4.30 375.97 84.22 11380.000 2750.00 484.32 6.30 160.84 66.49 11380.000 8250.00 488.09 6.42 383.88 85.72 11880.000 2750.00 486.68 4.98 167.22 68.75 11880.000 8250.00 489.68 7.87 401.28 89.58 D 12420.000 2750.00 488.14 5.14 174.52 70.66 12420.000 8250.00 491.72 7.95 417.39 92.80 12540.000 2750.00 488.51 4.83 176.30 71.21 12540.000 8250.00 492.49 6.36 422.04 93.71 12585.000 2750.00 488.56 4.59 176.96 71.36 12585.000 8250.00 492.08 9.84 423.43 93.98 12615.000 2750.00 488.58 4.58 177.37 71.41 12615.000 8250.00 492.18 9.83 424.02 94.08 12675.000 2750.00 488.65 4.69 178.27 71.62 12675.000 8250.00 493.88 4.99 426.27 94.47 E-32 n:-3 €6'lvl Mf699 6€'L 0~'61~ 00'0969 000'6900Z W'~01 vv'~8Z 96'v 89'91~ OO'~~ OOO'6900Z OL'Otl S€'S99 SV'Zl O9'LlS 00'0969 000'vv661 VV'V01 S9'€8Z 16'01 lS'v1S OO'~~ 000'vv661 06'6n lS'Z99 01"01 19'5lS 00'0969 000'V6L61 6O'V01 SL"Z8Z 9€'01 6V'nS OO'SZ~ 000'V6L61 6L"6n 66'199 81>"€1 6S'nS OO'OSZ8 000'6SL61 to'VOl SS'Z8Z 179'01 98'6OS OO'OSLZ 000'6SL61 99'6€1 LZ'l99 SO'€l 9t'ZlS OO'O~8 000'6OL61 ~6'tol ~'Z8Z S8'01 9t'SOS OO'O~LZ 000'6OL61 1~'6n 6€'099 01"6 9€'ZlS OO'O~S OOO'6S%1 SS'€01 88'l8Z SS'9 S1"SOS OO'OSLZ OOO'6S961 v€'6n LZ'6S9 €6'L 6Z'ZlS OO'OSZS 000'60961 ZL"EOl LE'l8Z SL"S to'SOS OO'OSLZ 000'60961 SO'LE1 ZS'Z179 26'9 61"01S OO'O~S OOO'6%Sl V6'101 66'ZLZ S1"V VV'9OS OO'OSLZ 000'69681 VL"9El LS.Qt9 €v'L 1L'6OS OO'O~S OOO't8881 0L"101 ZL"lLZ ~'v VZ'9OS OO'OSLZ 000.t8881 d It'9n 01"8€9 6S'L SO'6OS OO'OSZS 000'98LS1 €v'101 €Z'OLZ ~O'V lO'9OS OO'OSLZ OOO'98LSl OO'9€1 W'SE9 96'9 S9'SOS OO'O~S 000'OL981 60'101 8Z'89Z lS'€ LS'SOS OO'OSLZ 000'OL981 VS'€€l SL"L 19 LS'S SL"WS 00'OSZ8 OOO'~lSl Z1"66 9Z'9~ VV'Z O9'SOS OO'OSLZ OO(r~lSl lE'En OE'919 69'S L9'WS OO'OSZS 000'S80S1 S6'S6 EZ'SSZ ES'l LS'SOS OO'OSLZ OOO'S8081 It'zn S9'l19 vv'n lV'9OS 00'OSl8 000'OL6L 1 6Z'S6 SO'E~ W'S 19'VOS OO'OSLZ OOO'OL6L 1 €1"l11 179'~S It.s lS'%v OO'O~S 000.009t1 OZ'E8 LS'E1Z SS'V v6'26v OO'OSLZ OOO'OO9tl 3 ( !k)'oY) ~ ld -~J:>Y) {SQjJ "(ijJ ( SJ:> ) Uon~s 1r.>JV ~ggJ01S AtPOI~A '13SM.;) 0 {Y.)poold ~Anglnmtl;) ~Anglnmtl;) 'XOJddy (paOUPU03) vJ.va ;JnnwCLUI .!IO ..\lIVWWflS H;JNVlUI aOOMNOllO;J fl-:iI :fiRVJ. TABLE E-13 COITONWOOD BRANCH SUMMARY OF HYDRAUUC DATA (continued) Approx. Cumulative Cumulative Flooded Q CWSEL Velocity Storage Area Section (cfs) au !1P.ll ( Acre-Pt) (Acres ) 20279.000 2525.00 517.07 2.17 291.57 106.53 20279.000 6960.00 520.14 3.45 681.05 143.92 G 20479.000 2525.00 517.04 4.90 294.99 107.31 20479.000 6960.00 520.14 6.11 687.28 144.94 20779.000 2525.00 517.75 5.57 299.66 108.97 20779.000 6960.00 520.75 5.74 698.16 147.28 21989.000 2525.00 521.52 5.71 322.67 120.18 . 21989.000 6960.00 523.65 6.37 758.69 164.80 E-34 ~€-3 €1"L t€'61 €6' Z1"80~ 00'0~8 000'0191 ~€'~ 68'Zl 6t' O€. LO~ OO'O~€ 000'0191 81"~ t1"ll O~' 80'80~ OO'O~8 OOO'OLtl L9'€ 01"9 tZ. 6Z' LO~ OO'O~€ OOO'OLtl €6't ZO'Ol €~' 80'80~ OO'O~8 OOO.~t€l O~'€ €1"~ ~' 6Z'LO~ OO'O~€ OOO'~ttl L8't 88'6 9~'1 m'80~ 00'0~8 OOO'Qttl Lt'€ lO'~ €1"1 9Z'LO~ OO'O~€ OOO'Qttl ~t't Zt'6 tp'9 66'90~ 00'0~8 000'08Z1 81"€ tL"t L1"~ €~'90~ OO'O~€ OOO'08Z1 6€'t t€'6 L8'~ ZO'OO~ OO'O~8 000'09Z1 €1"€ 1L"t Z8't ~O'66t OO'O~€ 000'09Z1 gg'€ 8€'8 80'Z Zt'86t OO'O~8 OOO'OZll 08'Z ~'t 9L"1 ~0'L6t OO'O~€ OOO'OZll t6'Z tp'9 90'€ L~'%t 00'0001 000'016 €Z'Z O€.€ 6Z'Z 6Z'~6t oo.oot 000'016 00'1 €1"Z €€'€ 99'06t 00'0001 000'~6€ €L" 90'1 t9'Z €~'68t oo'oot 000'~6€ r-. 00' 00' OZ'9 zt'~ 00'0001 OOO'ZL 00' 00' 99.t t6'€8t oo'oot OOO'ZL l ~.oy) (ld-~.oy) {SQjJ mJ lSP) uO!l:Y.>S 1r.).IV ~gelO1S .uPOI~ A 'l3SM.::::> 0 ~POOH ~^!leInmn::::> ~^!lelnmn::::> 'XOJddy V.LVO ::>nnVllo..uI.1IO AlIVWWnS 1::> WVIDI.LS t1-~ ~'UlV.L TABLE E-15 STREAM C2 SUMMARY OF HYDRAUUC DATA Approx. Cumulative Cumulative Flooded Q CWSEL Velocity* Storage Area Section (cfs) !ID .(fl!ll ( Acre-Ft) (Acres) 275.000 225.00 482.30 3.43 .00 .00 275.000 550.00 483.77 4.30 .00 ~OO 672.000 225.00 488.42 4.60 .52 .26 672.000 550.00 490.05 6.00 1.00 .36 1118.000 225.00 496.07 3.51 1.10 .59 1118.000 550.00 497.46 4.07 2.16 .83 1510.000 225.00 500.93 3.26 1.71 .98 1510.000 550.00 502.08 4.69 3.35 1.36 E-36 APPENDIX F PLATES r- THE I i ./ .- COLONY I ./ ;II( ./ 423 LEBANON~./ ./ I ./~ ~OLAVILLE l 35 . CROWLEY . "" o 1 2 3 4 5 1_ _ 10 15 , SCALE IN FEET LEGEN>. r- @ @ @ PRO..ECT LOCATION ST ATE HIGHWAY IO?Sa . 151LOCWP.lXiN CITY-WIDE STORM WATER MANAGEMENT REPORT CITY OF COPPELL. TEXAS =~= ALBERT H. HALFF ASSOCIATES, INC. .0. ENGINEERS. SCIENTISTS - SURVEYORS PLATE 1 Jut y - 1990 FEDERAL HIGHWAY FEDERAL INTERSTATE HIGHWAY WATERSHED BOUNDARY '" TARRANT CQ\JNTY t"l DALLAS COU~ ~ ~ : : ~..J Gl :n )> ." m <: Z m '" o ~ )> :Ii ." o :n -; .' r m :;;: (ii <: ;= r m R BLVD. "'tI D II u DI ~ ~~ I I r- ... C : ~ 0.0 :0 G;~Q~ I I m ... > ."or ~ ro> I\) Z 0 85~5 >."z m> 0 ~ 0<0:ll .z ~o Zr ::0 >al"'o .",...c: "'al 3: m ren -I ~ s:: I~ C') m '-l<0:ll al 0 m :t:s:: en "'tIzCC'>:t: 0 s::s::C'>C'>"'tIm 0 ~Q > Ul~!6~ :llo'" 0 X -m z ~oG'>oC5 "T1 >zoo~>< r -a ;::; ~~~~ !;;r::ll ~ :0 G'>o ." m -a :0 :l:l"'0 " m :t:_ G'> r- c:::t s:: ::t c:.. C::O - ;I: "'l-l g g C1 ogZ\l\l~ Ci) i; m m< ~ om,...!;) <:ll;r: Z en 0 oc: r- C1~-I~:e r- ::0, o ~ r- m = ~g m r In I ;r:J:;r:o C'> AD c: mS:: I - m >. m :0 -lOO- m 3:::E > Z ~K-- ~ '" m'" en :!:! i!3 :0 ;c: I oo-<:oen~ Z 2l~ -l :2 >0>< ... z.< m en zo ~ C'> m ~6 z $ :l:l:l:len- . 5!l0 Z 0 m enm m>c:C'>o 0 :o:Or-~~ C "'l; >< 0 I\) I oz..,O ~ t.. >m g J:>!llUl <.". -I \l I -z I: r- en ;; ~ >>- -I c: > m m m en -I en E( -zzm-l::t ~ ~8 (fl G) 5: .Zo'" \l I -Ir-~ ~ m CQO:ll:ll :0 Z -<- \l :0 m z>mC::tO ~g 3: ~ ~~ m -I m a;G'> ~O~ ... m ~ en C'> -< c: - Z :0 (0 illJll z z ~ ;; I OJ > -I C'> mm :::j:O (0 -l .. > r- r- m c c: 01 !;) r- C1 I 0 ;; 0!2 engg en 0 m C'> z m 0 m c: r- <$ G'>::t ~ I en :0 60 :J:~ m m mm ~:o i! :om LEGEND FOR 100- YEAR FLOOD INUNDATION. LIMIT PLATES 179700 Iv\J\.J\J\J\J\..J 620 I 1730+00 - \J\J\J\J\fv'V\. 625 ...-- ---..... C) I I I I I I I I I ~ . 656.8 -0- -0- ~ -x ~ 24"S8 16"W 12"G F.F. CROSS SECTION 100 YEAR FLOOD INUNDATION LINE 100 YEAR FLOOD ELEVATION STREAM CENTERLINE WITH 1000 FOOT STATIONS 100 YEAR INUNDATION LINE WITH PROPOSED IMPROVEMENTS 100 YEAR FLOOD ELEVATION WITH PROPOSED IMPROVEMENTS STANDING WATER PROPERTY LINES TREE LINE RAILROAD TRACK STREETS EXISTING TRAILS BUILDINGS CONTOUR LINES SPOT ELEVATIONS POWER POLES FENCE LINE SANITARY SEWER LINE WATER LINE GAS LINE FINISHED FLOOR ELEVATION (FT.) CONTOUR INTERVAL IS 2 FEET STREAM STATIONS MEASURED IN MULTIPLES OF FIVE HUNDRED FEET PLATE 3 "0 ~ ... m 0.0 ... Co) I o r.. ~ en Ii 0 ~ "0 >>-l S6;Eo r- 1Il;z: ,,!l=l ~ 8,..i!: J!! m -< m 1_ ,..::D I ~"'." :.. ~~ - !I m~i5z .~ )(>mc iUl ~ ~ ~ g I ~ -4 ~ ... CD 8 o " :E )> ;;; " o ':l :;E :n )> z G') r m :;; < 2: Cl W I N BLVD. ciaO) ~ '\') ,-\3 ( .\.I.....")...\. L~-! -. ...,. --- / / , I ~ I OJ, m: ~: ; I : \ ..--' ...-- ---- ..~.. .'.I. /' C- "'--------- -- 2: m I 1D )> -",.<"" I -"1 '.. TARRANT COUNTY,. DALLAS COUNT~ I~ ~ : Q :L'I J > I :-U " ~ -. 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