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FS9904-SY 990326 I Conditional Letter of Map Revision (CLOMR) for Denton Creek I Schreiber Tract Coppell, Texas I I Payne Family Interests 5400 Renaissance Tower 1201 Elm Street Dallas, Texas 75270 I .t G. P£MBROKE 65143 Prepared by: Kimley-Horn and Associates, Inc. 12700 Park Central Drive Suite 1800 3' ~ - ~} ~ Dallas, Texas 75251 I Copyright © Kimley-Hom and Associates, Inc. March 1999 I ~ Kimley-Horn and Associates, Inc. I I/ _ ~}~~ Kimley-Horn PayneFamilylnterests and Associates, Inc. - Conditional Letter of Map Revision _ (CLOMR) for Denton Creek Schreiber Tract Coppell, Texas Prepared For: Payne Family Interests 5400 Renaissance Tower 1201 Elm Street Dallas, Texas 75270 Prepared By: Kimley-Hom and Associates, Inc. Suite 1800 12700 Park Central Drive -- Dallas, Texas 75251 (972)-770-1300 March 1999 \HYDRO\projects~06309306\Final\denton2.doc - ~]I~ Kimley-Horn Payne Family lnterests and Associates, Inc. - Table of Contents 1 Introduction .......................................................................................................................................................... 1 1.1Authority ........................................................................................................................................................... 1 1.2History .............................................................................................................................................................. 1 -- 1.3Purpose of Study ............................................................................................................................................... 1 1.4Location ............................................................................................................................................................ 2 -- 1.5General Site Characteristics .............................................................................................................................. 2 1.5.1 Topography .............................................................................................................................................. 2 1.5.2 Geotechnical Information ........................................................................................................................ 2 -- 1.6 Methodology ..................................................................................................................................................... 2 1.7 Results .............................................................................................................................................................. 2 _ 2. Hydrology ............................................................................................................................................................. 3 2.1 Method Description .......................................................................................................................................... 3 2.2 Model Description ............................................................................................................................................ 3. Hydraulics ............................................................................................................................................................. 3.1 Method Description .......................................................................................................................................... -- 3.2 Work Study Maps ............................................................................................................................................. 3.3 Parameter Estimation ........................................................................................................................................ 3.3.1 Roughness Coefficients ........................................................................................................................... 3.4 Cross Section Description ................................................................................................................................ 5 3.4.1 Duplicate Effective Model ....................................................................................................................... 5 3.4.2 Corrected Effective Models ..................................................................................................................... 5 3.4.3 Post Project Models ................................................................................................................................. 5 3.5 Floodway Modeling .......................................................................................................................................... 5 -- 3.6 Storage .............................................................................................................................................................. 6 3.7 Final Results ..................................................................................................................................................... 6 3.7.1 Hydraulic Analysis Results ...................................................................................................................... 6 - 3.7.2 Verification of Results ............................................................................................................................. 6 4. References ............................................................................................................................................................. 9 - ~i~ Kimley-Horn Payne Family lnterests and Associates, Inc, Appendices Appendix A: HEC-2 Models Duplicate Effective Models: - Duplicate Effective Floodplain - Duplicate Effective Floodway - Duplicate Effective Ultimate Conditions Corrected Effective Models: - Corrected Effective Floodplain - Corrected Effective Floodway - Corrected Effective Ultimate Conditions Post Project Models: - Post Project Floodplain - Post Project Floodway - Post Project Ultimate Conditions Appendix B: Exhibit Maps, Stream Profiles, and Cross-Sections Appendix C: FEMA Forms List of Tables _ Table 1: Manning's "n" Values ...................................................................................................................................... 4 Table 2: Comparison of Culmulative Volume/Storage for Ultimate ............................................................................. 6 -- Table 3: Comparison of Water Surface Elevations ........................................................................................................ 7 Table 4: Summary of Corrected Effective and Post-Project Hydraulics ....................................................................... 7 Table 5: Floodway Data Table - Post Project .............................................................................................................. 8 Table 6: Floodway Comparison Table .......... 8 This document, together with the concepts and designs presented herein, as an instrument of services intended only for the specific purpose and client for which it was prepared. Reuse of and improper reliance on this document without written authorization and adaptation by Kimley-Horn -- and Associates, Inc. shall be without liability to Kimley-Horn and Associates, Inc. Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL l\PROD~HYDRO\projects\06309306\Final\denton2.doc -ii- Kimle¥-Horn Payne Family lnterests and Associates, Inc. 1. Introduction 1.1 Authority Mr. Robert B. Payne, Sr. of Payne Family Interests retained the services of Kimley-Hom and Associates, Inc. for the evaluation of floodplain impacts to the Schreiber Tract located east of State Highway 121 and north of Denton Creek. This report will describe the overall characteristics of the proposed channel improvements to Denton Creek and the associated adjustments to the floodplain. It will also include all supporting technical documentation for the floodplain delineation. Acting on behalf of the client, contacts for the study are as follows: Roy Wilshire, P.E. William G. Pembroke, P.E. Michelle Evans, E.I.T. Kimley-Horn and Associates, Inc. 12700 Park Central Drive, Suite 1800 Dallas, Texas 75251 1.2 History Denton Creek and its watershed are located in portions of Dallas, Tarrant and Denton Counties. Denton -- Creek is a tributary of The Elm Fork of the Trinity River. Denton Creek encompasses a total drainage area of 719 square miles, with a current 100-year discharge of 23,083 cubic feet per second (cfs). This - drainage area includes the Grapevine Lake drainage area of 695 square miles. The remaining 24 square mile drainage area includes portions of the cities of Grapevine, Flower Mound, Lewisville, Carroilton, -- and Coppell. Also included is a 7 square mile watershed area draining to Cottonwood Branch, a major tributary of Denton Creek. 1.3 Purpose of Study Portions of the affected property currently lie within a Federal Emergency Management Agency (FEMA) designated Zone AE, which is an area of 100-year flooding with base flood elevations and flood hazard factors determined. The remaining portion of the property is designated as Zone X, which is an area Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOLl\PROD\HYDRO\projects\06309306\Final\denton2.doc - 1- and Associates, Inc, outside the 100-year floodplain. -- The purpose of this study is to quantify the portion of the site which can be reclaimed from the 100-year floodplain and to request a Conditional Letter of Map Revision based on the results of this analysis. 1.4 Location -- The site is located near the northeast comer of the intersection of SH 121 and Denton Creek. The site is bounded by SH 121 to the west, SH 121 Bypass to the north, Denton Creek to the south, and undeveloped property to the east (see Appendix B). 1.5 General Site Characteristics 1.5.1 Topography The upland areas of the site are vegetated with medium to dense brush and trees along with some grassy _ open areas. The low-lying areas adjacent to the channel are a combination of light to medium brush and trees. The existing Denton Creek channel varies in bottom width from 20 to 30 feet with side slopes from 1:1 to 2:1 and is moderately eroded throughout the property. 1.5.2 Geotechnical Information Soils within the site are primarily of the Frio and Bastrop series which consist of clays and loams _ 1.6 Methodology This flood study was completed using standard hydrologic and hydraulic methods. The hydrologic values were obtained from the effective FEMA hydraulic models. These values are based on an existing watershed. Hydraulic conditions were modeled using the standard methods for the City of Coppell and the HEC-2 computer model. Details of this methodology are provided in the following chapters of this report. 1.7 Results The limits of flooding for the 100-year flood event are shown in Appendix B. Schreiber Tract (Denton Creek) March 1999 G:\HYDRO\proj ects\06309306\Final\denton2 .doc -2- and Associates, Inc. 2. Hydrology 2.1 Method Description Discharge values were obtained from the effective FEMA FIS and are consistent with the City-Wide Stormwater Management Study completed for the City of Coppell by Albert H. Halff Associates, Inc, in January 1991. -- 2.2 Model Description The Floodplain Models (Duplicate Effective, Corrected Effective and Post Project) discharge values within project limits: -- 10 year 10,000 cfs 50 year 13,800 cfs 100 year 15,600 cfs _ 500 year 36,200 cfs The Floodway Models (Duplicate Effective, Corrected Effective and Post Project) discharge values -- within project limits: 100 year 15,600 cfs The Ultimate Conditions* Models (Duplicate Effective, Corrected Effective and Post Project) discharge values within project limits: ,. 2 year 5,645 cfs -- Base Flows 10,168 cfs Standard Project Flood 14,753 cfs ~ 100 year Fully Developed 16,681 cfs - 500 year 36,200 cfs * per City of Coppell Floodplain Management Ordinance No. 94639 Schreiber Tract (Denton Creek) March 1999 "- \\RANGER\VOL I ~PROD\HYDRO\projects\06309306~Final~denton2.doc -3- - ~l~ Kimley-Horn PayneFamilylnterests and Associates, Inc. 3. Hydraulics 3.1 Method Description The hydraulic models for this study were prepared based on two-foot aerial topography, field visits, and previously completed studies and reports. The City-Wide Stormwater Management Study, January 1991, was obtained from the City of Coppell. It was used, along with available site plans, to develop the backwater model for this study. 3.2 Work Study Maps The floodplain limits for the study are shown in Appendix B. 3.3 Parameter Estimation 3.3.1 Roughness Coefficients Roughness coefficients (Manning's "n" Values) used in the hydraulic computations were based on Open Channel Hydraulics [Chow, 1959], engineering judgment, and field observation of the channels and floodplain areas. A summary of the Manning's "n" values used is shown in Table 1. Table 1' Manning's "n" Values Manning's "n" Value River Station Left Overbank Main Channel Right Overbank Source/Location 349+50 .05-.06 .045 .055 Effective Model 357+00 .05-.06 .045 .055 Effective Model 362+50 .055-.06 .045 .04 Effective Model 369+70 .05-.06 .045 .5-.06 Effective Model 376+00 .045-.055 .045 .045-.055 Proposed Project 378+00 .045~.055 .045 .045-.055 Proposed Project 380+50 .045-.06 .045 .045-.055 Proposed Project 382+00 .045-.06 .045 .045-.055 Proposed Project 385+50 .045-.06 .045 .045-.05 Proposed Project 392+90 .045-.055 .045 .045-.055 Proposed Project 394+40 .055-.06 .045 .055-.06 Effective Model 394+90 .055-.06 .045 .05-.055 Effective Model 395+40 .055 .045 .05-.055 Effective Model Schreiber Tract (Denton Creek) March 1999 -- \~RANGER\VOL 1 \PROD\HYDRO,projects\06309306\Final\denton2.doc -4~ and Associates, Inc. 3.4 Cross Section Description -- 3.4.1 Duplicate Effective Model The Existing Conditions FIS Models (Floodplain, Floodway, and Ultimate Conditions) were obtained from Dunaway Associates. Dunaway Associates received a Conditional Letter of Map Revision (CLOMR) from FEMA for the Mansions on the Lake multi-family developments located opposite the Schreiber Tract on Denton Creek. This development was constructed as proposed in the CLOMR; therefore Dunaway and Associates was to submit the CLOMR models for a Letter of Map Revision (LOMR). As a result, these models would become the effective FEMA models. The HEC-2 computer models obtained from Dunaway Associates were run to verify results. The three models were subsequently relabeled "Duplicate Effective Models". Model results for the 100 year discharge, within project limits, are summarized in Table 3 with computer output files located in Appendix A. 3.4.2 Corrected Effective Models _ The Duplicate Effective Models were supplemented by the addition of water surface elevations for the existing ponds within the project limits (between sections 376+00 and 392+90). The resulting models _ were used to determine the baseline existing conditions 100-year water surface elevation within the project limits. Model results for the 100 year discharge are summarized in Tables 3, 4, 5,and 6, with computer output files located in Appendix A. 3.4.3 Post Project Models The Post Project models are based on modifications to the Corrected Effective models to reflect proposed channel improvements. The modifications to the Corrected Effective models consist of lowering the -- ground points in the left overbank to an elevation of approximately 459 ft. from section 376+00 to 392+90. A portion of the floodplain will be filled to approximately 467 ft. and sloped (4:1) down to the -- left overbank elevation of 459 ft. The modified overbank will be revegetated to stabilize the side slopes. Cross sections 376+00 to 392+90 were modified in order to properly model the proposed floodway - modification. Model results are summarized in Tables 3, 4, 5,and 6 with computer output files in Appendix A. FEMA forms and cross section plots can be found in Appendix B. 3.5 Floodway Modeling _ Floodway limits were modified as part of this study. The floodway model was revised to include the proposed overbank modifications. Model results are summarized in Tables 5 and 6. Schreiber Tract (Denton Creek) March 1999 -- \\RANGER\VOL 1 \PROD\HYDRO\projects\06309306\Final\denton2.doc -5- and Associates, Inc, 3.6 Storage The corrected ultimate condition model cumulative storage volume was checked at the up and down stream limits of the property. The net increase between the corrected ultimate conditions model and the _ post project ultimate conditions model was 0.7 Acre Feet Table 2: Comparison of Cumulative Volume for Ultimate Conditions 100-Year Volume (Acre-fO River Ultimate Station Conditions Corrected Effective Post-Project Net Change Discharge (cfs) 369+70 16681 495.83 495.83 0.0 376+00 16681 561.56 562.00 0.44 378+00 16681 583.09 583.48 0.39 380+50 16681 626.45 630.53 4.08 382+00 16681 648.39 653.95 5.56 385+50 16681 700.31 705.32 5.01 392+90 16681 819.03 820.76 1.73 394+40 16681 845.23 845.93 0.7 3.7 Final Results 3.7.1 Hydraulic Analysis Results -- As a result of the left overbank excavation and fill, Post Project BFE's did not increase when compared to the Corrected Effective BFE's. Tables 3, 4, 5,and 6 show the hydraulic modeling results of the 100 year -- discharge for Denton Creek from cross section 369+70 to cross section 394+40. 3.7.2 Verification of Results The results were evaluated by comparing them with available FEMA FIS and other reports mentioned _ previously in this study. The results reflect no increase in the BFE's in the subject property. This is consistent with expectations and indicates the reasonableness of the overall results of this analysis. Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL l\PROD\HYDRO\projects\06309306\Final\denton2.doc -6- ~~~ Kimley-Hom Payne Family lnterests Table 3: Comparison of Water Surface Elevations River 100-Year Water Surface Elevations Station Discharge (c~) Duplicate Effective Corrected Effective Post-Pr~ect 369+70 15600 464.40 464.40 464.40 376+00 15600 465.39 465.41 465.38 378+00 15600 465.43 465.45 465.41 380+50 15600 465.52 465.55 465.48 382+00 15600 465.56 465.65 465.53 385+50 15600 465.71 465.86 465.64 392+90 15600 466.01 466.21 465.92 394+40 15600 465.52 465.77 465.33 Table 4: Summary of Corrected Effective and Post-Project Hydraulics River 100 year Water Surface Elevations Net Change in 100-Year Velocity Water Surface Station Corrected Effective Post-Project (fl) Corrected Effective Post-Project 369+70 464.40 464.40 0.0 7.66 7.66 376+00 465.41 465.38 -0.03 3.56 3.23 378+00 465.45 465.41 -0.04 3.66 3.19 380+50 465.55 465.48 -0.07 4.20 3.53 382+00 465.65 465.53 -0.12 4.08 3.60 385+50 465.86 465.64 -0.22 3.83 3.96 392+90 466.21 465.92 -0.29 3.76 3.69 394+40 465.77 465.33 -0.44 8.45 9.10 Schreiber Tract (Denton Creek) March 1999 - \XRANGER\VOL l\PROD\HYDRO\projects\06309306\Final~denton2.doc -7- and Associates, Inc. Table 5: Floodway Data Table - Post Project Floodway Base Flood Water Surface Elevation River Section Area Mean Velocity Without With Increase Station Width (fl^2) (f~s) Floodway Floodway 369+70 920 3257 4.8 464.4 465.1 0.7 376+00 930 7370 2.1 465.4 465.9 0.5 378+00 751 6845 2.3 465.4 465.9 0.5 380+50 721 6255 2.5 465.5 466.0 0.5 382+00 712 5911 2.6 465.5 466.0 0.5 385+50 690 5942 2.6 465.6 466.1 0.5 392+90 800 6668 2.3 465.9 466.3 0.4 394+40 593 2272 6.9 465.4 465.8 0.4 Table 6: Floodway Comparison Table River Corrected Effective Post Pr~ect Net Floodway Station with Floodway with Floodway Elevation Change 369+70 465.1 465.1 0.0 376+00 465~9 465.9 0.0 378+00 465.9 465.9 0.0 380+50 466.0 466.0 0.0 382+00 466.1 466.0 -0.1 385+50 466.3 466.1 -0.2 392+90 466.6 466.3 -0.3 394+40 466.1 465.8 -0.3 Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL 1 \PROD\HYDRO\projectsX06309306\Final~denton2.doc -8- Kimley-Horn Payne Family Interests and Associates, Inc. 4. References 1. Albert H. HalffAssociates, Inc. City-Wide Storm Water Management Study, Coppell, Texas, 1991. 2. Flood Insurance Rate Map, City of Coppell, Texas, Panel 480170 0010E 3. Army Corp of Engineers., User Manual for HEC-2, September 1991 4. Yen Te Chow, Open-Channel Hydraulics, 1959 Schreiber Tract (Denton Creek) March 1999 \\RANGERXVOL l\PROD\HYDRO\projects\06309306\Final\denton2.doc -9- Kimley-Horn payne Family Interests and Associates, Inc. Appendix A: HEC-2 Models Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL 1 ~PROD\HYDRO\projects\06309306\Final\denton2.doc Kimley-Horn Payne Family Interests and Associates, Inc. Duplicate Effective Models Duplicate Effective Floodplain Duplicate Effective Floodway Duplicate Effective Ultimate Conditions Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL 1 \PROD\HYDRO\projects\06309306\Final\denton2.doc Kimley-Horn Payne Family Interests and Associates, Inc. Duplicate Effective Floodplain Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL 1 \PRODLHYDRO\projects\06309306\Final\denton2.doc Duplicate Effective Floodway Schreiber Tract (Denton Creek) March 1999 \W, ANGER\VOL 1 \PROD\HYDRO\projects\06309306\Final\denton2.doc and Associates, Inc. Duplicate Effective Ultimate Conditions Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL 1 \PROD\HYDRO\projects\06309306\Final\denton2.doc Kimley-Horn Payne Family Interests '- and Associates, Inc, Corrected Effective Models Corrected Effective Floodplain Corrected Effective Floodway Corrected Effective Ultimate Conditions Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL 1 \PROD\HYDRO\projects\06309306\Final\denton2.doc Kimley-Horn Payne Family Interests - and Associates, Inc. Corrected Effective Floodplain Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL 1 ~PROD\HYDRO\projects\06309306\Final\denton2.doc Kimley-Horn Payne Family interests and Associates, Inc. Corrected Effective Floodway Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL 1 ~PROD\HYDRO\projects\06309306\Final\denton2.doc and Associates, Inc. Corrected Effective Ultimate Conditions Schreiber Tract (Denton Creek) March 1999 ~ \LRANGER\VOL 1 ~PROD\HYDRO\projects\06309306\Final\denton2.doc and Associates, Inc. Post Project Models - Post Project Floodplain Post Project Floodway Post Project Ultimate Conditions Schreiber Tract (Denton Creek) March 1999 \XRANGER\VOL 1 ~PROD\HYDRO\projects\06309306\Final\denton2.doc Kimley-Horn Payne Family Interests - and Associates, Inc. Post Project Floodplain Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL 1 \PROD\HYDRO\projects\06309306xFinal\denton2.doc Kimley-Horn Payne Family Interests and Associates, Inc. Post Project Floodway Schreiber Tract (Denton Creek) March 1999 \XRANGER\VOL I \PROD\HYDRO\projects\06309306\Final\denton2.doc Kimley-Horn Payne Family Interests and Associates, Inc. Post Project Ultimate Conditions Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL lXPROD\HYDRO\projects\06309306\Final\denton2.doc and Associates, Inc, Appendix B: Exhibit Maps, Stream Profiles, and Cross-Sections Vicinity Map Floodplain Work Map Annotated FIRM Panel Flood Profiles Cross Sections (Post Project) Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL 1 \PROD\HYDRO\projects\06309306\Final\denton2.doc - and Associates, Inc. Appendix C: FEMA Forms Schreiber Tract (Denton Creek) March 1999 \\RANGER\VOL 1 hnROD\HYDRO\projects\06309306\Final\denton2.doc FEDERAL EMERGENCY MANAGEMENT AGENCY I O.M.B No. 3067-0148 REVISION REQUESTER AND COMMUNITY OFFICIAL~ Expires April 30, 2001 Public reporting burden for this form is estimated to average 2.13 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing and reviewing the form. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Federal Emergency Management Agency, 500 C Street, S.W., Washington DC 20472; and to the Office of Management and Budget, Paperwork Reduction Proiect (3067-0148), Washington, DC 20503. You are not required to respond to this collection of information unless a valid OMB Control Number is displayed in the upper right corner of this form. 1. REQUESTED RESPONSE FROM FEMA This request is for a: [] CLOMR A letter from FEMA commenting on whether a proposed project, if built as proposed, would justify a map revision, or proposed hydrology changes (See 44 CFR Ch. 1, Parts 60,65 & 72). [] LOMR A letter from FEMA officially revising the current NFIP map to show the changes to floodplains, floodway or flood elevations. LOMRs typically decrease flood hazards. (See 44 CFR Ch. 1 Parts 60 & 65.) [] Other Describe: 2. OVERVIEW 1. The basis for this revision request is {are): (check all that apply) [] Physical Change [] Improved Methodology/Data [] Floodway Revision [] Other Describe: Note: A photograph is not r-e-q~r~d, but is very helpful during review. 2. Flooding Source: Denton Creek 3. Project Name/Identifier: Letter of Map Revision for Denton Creek 4. FEMA zone designations affected: AE,X (example: A, AH, AO, Al-A30, A99, AE, V, V1-V30, YE, B, C, D, X) 5. The NFIP map panel(s) affected for all impacted communities is (are): Community No. Community Name State Map No. Panel No. Effective Date Ex: 480301 Katy, City TX 480301 000SD 02/08/83 480287 Harris County TX 48201C 0220G 09/28/90 480170 Coppell, City TX 480170 0010E 04/15/94 Dallas County 6. The area of revision encompasses the following types of flooding and structures. Check all that apply. Types of Flooding Structures [] Riverine [] Channelization r"]' Coastal [] Levee/Floodwall [] Alluvial fan [] Bridge/Culvert [] Shallow Flooding (e.g. Zones AO and AH) [] Dam [] Lakes [] Fill [] Other (describe) [] Other (describe) FEMA Form 81-89 Revision Requester and Community Official Form MT-2 Form 1 Page 1 of 2 4. ENCROACHMENT INFORMATION 1. Does the State have jurisdiction over the floodway or its adoption by communities participating in the NFIP? [] Yes [] No If Yes, attach a copy of a letter notifying the appropriate State agency of the floodway revision and documentation of the approval of the revised floodway by the appropriate State agency. 2. Does the development in the floodway cause the 1% annual chance (base) elevation to increase at any location by more than 0.000 feet? [] Yes [] No [] N/A 3. Does the cumulative effect of all development that has occurred since the effective SFHA was originally identified cause the base flood elevation to increase at any location by more than one foot (or other increase limit if community or state has adopted mere stringent criteria- even if a floodway has not been delineated by FEMA)? [] Yes [] No If the answer to either items is Yes, please attach documentation that all requirements of Section 65.12 of the NFIP regulations have been met, regarding evaluation of alternatives, notice to individual legal property owners, concurrence of CEO, and certification that no insurable structures are impacted. 5. MAINTENANCE RESPONSIBILITY The community is willing to assume responsibility for [] performing [] overseeing compliance with the maintenance and operation plans of the __ (Name) flood control structure. If not performed promptly by an owner other than the community, the community will provide the necessary services without cost to the Federal government. Operation and maintenance plans are attached. [] Yes [] No [] N/A 6. REVIEW FEE The review fee for the appropriate request category has been included. [] Yes Fee amount: $3100 OR This request is based on a federally sponsored flood-control project where 50 percent or more of the project's cost is federally sponsored, or the request is based on detailed hydrologic and hydraulic studies conducted by Federal, State, or local agencies to replace approximate studies conducted by FEMA and shown on the effective FIRM; thus the project is fee exempt. [] Yes Please see Instructions for Fee Amounts 7. SIGNATURE Note: I understand that my signature indicates that all information submitted in Note: Signature indicates that the community understands, from the revision support of this request is correct requester, the impacts of the revision on flooding conditions in the community. Signature of Community Official Signature of Revision Requester ..... Printed Name and Title of Communit7 Official Pdnted Name and Title of Revision Requester Cib/of Coppell Community Name Company Name Telephone No.: ..... Date: ..... Telephone No.: ..... Date: ..... CERTIFICATION BY REGISTERED PROFESSIONAL ENGINEER AND/OR Check which forms have been included with this request LAND SURVEYOR This certification is in accordance with 44 CFR Ch. 1, Sect 65.2 Form Name and (Number) Required if ...... [] Hydrologic (3) new or revised discharges [] Hydraulic (4) new or revised water-surface elevations Signature [] Mapping (5) floodplain/floodway changes [] Channelization (6) channel is modified [] Bridge/Culvert (7) addition/revision of bridge/culvert Printed Name and Title of Revision Requester [] Levee/Floodwall (8) addition/revision of levee/floodwall [] Coastal (9) new or revised coastal elevations Registr No. _ .... Expires (Date) ..... State ..... [] Coastal Structures (10) addition/revision of coastal structure [] Dam (11) addition/revision of dam Type of License/Expertise: ..... [] Alluvial Fan (12) structures proposed on alluvial fan -- FEMA Form 81-89 Revision Requester and Community Official Form MT-2 Form 1 Page 2 of 2 FEDERAL EMERGENCY MANAGEMENT AGENCY ! O.M.B No. 3067-0148 RIVERINE HYDRAULIC ANALYSIS ~ Expires April 30, 2001 PUBLIC BURDEN DISCLOSURE NOTICE Public reporting burden for this form is estimated to average 2.25 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing and reviewing the form. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Federal Emergency Management Agency, 500 C Street, S.W., Washington DC 20472; and to the Office of Management and Budget, Paperwork Reduction Proiect {3067-0148), Washington, DC 20503. You are not required to respond to this collection of information unless a valid OMB Control Number is displayed in the upper right corner of this form. Note: Fill out one form for each flooding source studied Community Name: City of Coppell Flooding Source: Denton Creek Project Name/Identifier: Letter of Map Revision for Denton Creek 1. REACH TO BE REVISED Describe the limits of the revision OR submit a copy of the FIRM with the revision area clearly highlighted. Copy of FIRM(s) attached depicting area of the revision (highlighted, or circled)? [] Yes Downstream Limit: Section 376 + 00{ Ref HEC-2 Input/Output, Appendix C) Upstream Limit: 392 + 90 ( Ref HEC-2 Input/Output, Appendix C) 2. MODELS SUBMITTED Requirements: for areas which have detailed flooding: for areas which do not have detailed Full input and output listings along with files on diskette for each of the models flooding: listed below (items 1-4) and a summary of the source of input parameters used Only the 100-year (Base) flood profile is in the models must be provided. The summary must include a description of any required. A hydraulic model is not required changes made from model to model (e.g., Duplicate Effective model to for areas which do not have detailed Corrected Effective model). At a minimum, the Duplicate Effective (item 1) and flooding; however, BFEs may not be added to the Revised or Post-Project Conditions titem 4} models must be submitted. See the revised FIRM. If a hydraulic model is instructions for directions on when other models may be required, developed for the area, items 3 and 4 described below must be submitted. If hydraulic models are not developed, hydraulic analyses (including all calculations) for existing or pre-project conditions and revised or post-project conditions must be submitted. 1. Duplicate Effective Model [] Natural File Name dcfpdup.dat [] Floodway File Name dcfwdup.dat Copies of the hydraulic analysis used in the effective FIS, referred to as the effective models (10-, 50-, 100-, and 500-year multi-profile runs and the floodway run) must be obtained and then reproduced on the requester's equipment to produce the Duplicate Effective model. This is required to assure that the effective models input data has been transferred correctly to the requester's equipment and to assure that the revised data will be integrated into the effective data to provide a continuous FIS model upstream and downstream of the revised reach. 2. Corrected Effective Model [] Natural File Name dcfpcor.dat [] Floodway File Name dcfwcor.dat The Corrected Effective model is the model that corrects any errors that occur in the Duplicate Effective model, adds any additional cross sections to the Duplicate Effective model, or incorporates more detailed topographic information than that used in the currently effective model. The Correctly Effective model must not reflect any man-made physical changes since the date of the effective model. An error could be a technical error in the modeling procedures, or any construction in the floodplain that occurred prior to the date of the effective model but was not incorporated into the effective model. 3. Existincj or Pre-Project Conditions Model [] Natural File Name NA [] Floodway File Name NA The Duplicate Effective model or Corrective Effective model is modified to produce the Existing or Pre-Pr~ct Conditions model to reflect any modifications that have occurred within the floodplain since the date of the Effective model but prior to the construction of the project for which the revision is being requested. If no modification has occurred since the date of the effective model, then this model would be identical to the Corrected Effective model or Duplicate Effective model. 4. Revised or Post-Project Conditions Model [] Natural File Name dcfppst.dat [] Floodway File Name dcfwpst.dat The Existing or Pre-Project Conditions model (or Duplicate Effective model or Corrected Effective model, as appropriate) is revised to reflect revised or post-project conditions. This model must incorporate any physical changes to the floodplain since the effective model was produced as well as the effects of the project. When the request is for the proposed project this model must reflect proposed conditions. 5. Other - Please attach a sheet describing all other models submitted along with the file names. [] Natural [] Floodway PLEASE REFER TO THE INSTRUCTIONS FOR THE APPROPRIATE MAILING ADDRI=$S FEMA Form 81-89C Riverine Hydraulic Analysis Form MT-2 Form 4 Page 1 of 2 3. STARTING WATER-SURFACE ELEVATIONS I Explain how they were determined. Explanation Attached? [] Yes [] No NOTE: If the effective study is an approximate study, the slope/area method is recommended. For detailed analysis studies, using a known water-surface elevation is recommended. 4. RESULTS (from the model used to revise the 100-year water surface elevations) If the results indicate any of the following, attach an explanation - to this form, or to the hydraulic model printout- as to the reasonableness of the situation. [] Supercritical depth [] Critical Depth [] Drawdowns [] Negative Floodway Surcharges [] Floodway Surcharges Greater Than Maximum Allowed by Community/State [] Water surface elevations higher than the end points of cross sections. [] Floodway discharge is different than the Natural 100-year (base) flood discharge. [] Project causes lO0-year floodplain or floodway elevations to increase (state if increases are located off the requester's property) Explanation attached with Form [] Explanation provided on attached printout [] If Hydraulic model used is HEC-2, has it been checked with FEMA'S CHECK-2 computer program? [] Yes [] No (see instructions for information on how to obtain CHECK-21 5. REVISED FIRM/FBFM AND FLOOD PROFILES 1. Profile Transition a. 100-Year Water-Surface Elevations - indicate the difference in water surface elevations where the project 100-year elevations tie into the existing 100-year water surface elevations at each end of the project. Downstream End 369 + 70 within O (feet) Upstream End 394 + 40 within .44 (feet) Cross-Sect/on It Cross-Sect/on # b. Floodway Elevations - indicate the difference in water surface elevations where the project floodway elevations tie into the existing floodway water surface elevations at each end of the project. Downstream End 369 + 70 within 0 (feet) Upstream End 394 + 40 within .30 (feet) Cross-Section # Cross-Section it c. Floodway widths - indicate the difference in floodway widths where the project floodway widths tie into the existing floodway width at each end of the project. Downstream End 369 + 70 within O (feet) Upstream End 394 +40 within O (feet) Cross-Sect/on It Cross-Sect/on it 2. Profile Checklist (check box if information has been provided on profile) The following information (unless in parentheses) must be included at the same scale as the existing profiles for this project: [] Stream Name [] Community Name [] Corporate Limits labeled [] Study limits labeled [] Confluences labeled [] Channel Stationing [] Streambed profiled [] Cross Sections labeled [] Horizontal/Vertical Scales indicated [] 100-¥ear elevs profiled* [] Road Crossings [] Labeled [] Low Chord Elevations [] Top of Road Elevations *All recurrence intervals in the effective study must also be profiled. Floodway Data Table Attach a Floodway Data Table for each cross section listed in the published Floodway Data table in the FIS report. Floodway Data Table Attached [] Yes [] Not Required FEMA Form 81-89C Riverine Hydraulic Analysis Form MT-2 Form 4 Page 2 of 2 FEDERAL EMERGENCY MANAGEMENT AGENCY ! O.M.B No. 3067-0148 RIVERINE / COASTAL MAPPING ~ Expires April 30, 2001 PUBLIC BURDEN DISCLOSURE NOTICE Public reporting burden for this form is estimated to average 1.5 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing and reviewing the form. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Federal Emergency Management Agency, 500 C Street, S.W., Washington DC 20472; and to the Office of Management and Budget, Paperwork Reduction Project (3067-0148), Washington, DC 20503. You are not required to respond to this collection of information unless a valid OMB Control Number is displayed in the upper right corner of this form. Note: Fill out one form for each flooding source studied Community Name: City of Coppell Flooding Source: Denton Creek Project Name/Identifier: Letter of MaD Revision for Denton Creek This is a [] Manual [] Digital submission. Digital map submissions may be used to update digital FIRMs (DFIRMs). For updating DFIRMs, these submissions must be coordinated with FEMA Headquarters as far in advance as possible. 1. MAPPING CHANGES 1. A topographic workmap must be submitted showing the following information (check N/A when not applicable): a. Revised approximate lO0-year floodplain boundaries (Zone A) .................................................. [] Yes [] No [] N/A b. Revised detailed 100- and 500-year floodplain boundaries ....................................................... [] Yes [] No [] N/A c. Revised floodway boundaries ............................................................................................... [] Yes [] No [] N/A d. Location and alignment of all cross sections with stationing control indicated ............................ [] Yes [] No [] N/A e. Stream alignments, road alignments and dam alignments ........................................................ [] Yes [] No [] N/A f. Current community boundaries ............................................................................................ [] Yes [] No [] N/A g. Effective 100- year floodplain and floodway boundaries from FIRM/FBFM reduced or enlarged to the scale of the topographic workmap .................................................................. [] Yes [] No [] N/A h. Tie-ins between the effective and revised 100-, 500-year and floodway boundaries .................... [] Yes [] No [] N/A i. The requester's property boundaries and community easements ............................................... [] Yes [] No [] N/A j. The signed certification of a registered professional engineer .................................................... [] Yes [] No [] N/A k. Location and description of reference marks ........................................................................... [] Yes [] No [] N/A I. Vertical datum (example: NGVD, NAVD) ............................................................................... [] Yes [] No [] N/A m. Coastal zone designations tie into adjacent areas not being revised ........................................... [] Yes [] No [] N/A n. Location and alignment of all coastal transects used to revise the coastal analyze ....................... [] Yes [] No [] N/A o. V-zone has been delineated to extend landward to the heel of the primary frontal dune ............... [] Yes [] No [] N/A If any items are marked No or NIA please attach an explanation. 2. What is the source and date of the updated topographic information (example: orthophoto maps, July 1985; filed survey, May 1979, beach profile, June 1987 etc.)? 3. What is the scale and contour interval of the following workmaps? Effective FIS Scale 1"=200' Contour Interval 2' Revision Request Scale 1"=200' Contour Interval 2' NOTE: Revised topographic information must be of equal or greater detail than effective. 4. Attach an annotated FIRM/FBFM at the scale of the effective FIRM/FBFM showing the revised 100- and 500-year floodplain and the floodway boundaries and how they tie into those shown on the effective FIRM/FBFM downstream and upstream of the revisions or adjacent to the area of revision for coastal studies. FIRM/FBFM attached? [] Yes [] No PLEASE REFER TO THE INSTRUCTIONS FOR THE APPROPRIATE MAILING ADDRESS FEMA Form 81-89D Riverine / Coastal Mapping Form MT-2 Form 5 Page 1 of 2 -- 2. EARTH FILL PLACEMENT 1. The fill is: [] Existing [] Proposed 2. Has fill been/will be placed in the regulatory floodway? [] Yes [] No If Yes, please attach completed River)ne Hydraulic Analysis Form (Form 4). 3. Has fill been/will be placed in floodway fringe (area between the floodway and lO0-year floodplain boundaries)? [] Yes [] No If Yes, then complete A, B, C, and D below. a. Are fill slopes for granular materials steeper than one vertical on one-and-one-half horizontal? [] Yes [] No If Yes, justify steeper slopes b. Is adequate erosion protection provided for fill slopes exposed to moving flood waters? (Slopes exposed to flows w/th velocities of up to 5 feet per second (fps) during the lO0-year flood must, at a minimum, be protected by a cover of grass, vines, weeds, or similar vegetation; s/opes exposed to flows w/th velocities greater than 5 fps during the lO0-year flood must, at a minimum, be protected by stone or rock riprap.} [] Yes [] No If No, describe erosion protection provided ..... c. Has all fill placed in revised lO0-year floodplain been compacted to 95 percent of the maximum density obtainable with the Standard Proctor Test Method or acceptable equivalent method? [] Yes [] No d. Can structures conceivably be constructed on the fill at any time in the future? [] Yes [] No If Yes, attach certification of fill compaction (item 3c. above) by the community's NFIP permit official, a registered professional engineer, or an accredited soils engineer in accordance with Subparagraph 65.5(a)(6) of the NFIP regulations. Fill certification attached [] Yes [] No 4. Has fill been/will be placed in a V zone? [] Yes [] No If Yes, is the fill protected from erosion by a flood control structure such as a revetment or seawall? [] Yes [] No If Yes, attach the Coastal Structures Form (Form 10). FEMA Form 81-89D River)ne/Coastal Mapping Form MT-2 Form 5 Page 2 of 2