Parks Coppell FS-CS 890126 Federal Emergency Management Agencyacc'
Washington, D.C. 20472 ~c ~
The Honorable Lou Duggan 89-06-06R Case No.:
Mayor of the City of Coppell ~
P.O. Box 478 ~~(~
Coppell, Texas 75019
Dear Mayor Duggan: ~
This is in reference to a letter October 10, 1988, and a floodplain
study submitted by Mr. Russell R. Doyle, P.E., City Engineer for the City of
Coppell. In his letter, which was forwarded to us by our Region VI office,
Mr. Doyle requested a conditional Letter of Map Revision (LOMR) for a proposed
fill ~roject along Cottonwood Branch and Denton Creek on behalf of Jerry
Parche Consulting Engineers. The submitted floodplain study entitled Flood-
plain Reclamation Study on Co~tonwood Branch and Denton Creek, dated October
1988, prepared by Jerry Parche Consulting Engineers, included the following:
a description of the methodologies used; HEC-2 models of Denton Creek and
Cottonwood Branch representing existing and proposed conditions; and delineations
of the existing and proposed 100-year floodplain boundaries and the proposed
regulatory floodway boundaries on a topographic map. Prior to the commencement
of our review, we received the initial fee of $350.00 for processing a conditional
L0~R request of this type. This fee was sufficient to cover the review and
processing costs associated with this submittal.
As explained in the submitted floodplain study, additional cross sections were
inserted into the ~EC-2 models for Denton Creek and Cottonwood Branch (in the
Vicinity of Denton Tap Road), which are not refle~£e~-~-~--'~-~r~l~h~ry Flood
Insurance Study (FIS) for the City of Coppell, dated Sep~e--mber 22, ~988.
These modei~-~' ~h~-~-o~e the best available models ~-~'ii-~-'used as the
new baseline models in order to evaluate the effects of the proposed proj'e6t.
swale construction and floodplain fill project known as the Mag__n~li__a p~roj.e~t~ .
we have recently receive~ a request for ~ map rev~-s'ion from your community
regarding the Magnolia project and are currently awaitl-h-g--~]~-ission of a
written maintenance agreement for this project as specified under Part 65.6
-(a)(12) of the National Flood Insurance Program (NFIP) regulations. Therefore, -~
t~e preliminary FIS will not be revised to reflect the updated existi~~ '
conditions until the aforementioned mainte~c~-~-~n{'-is-'re6eived.
After reviewing the submitted data, we have determined that the proposed fill
project meets the minimum floodplain management criteria of the NFIP. If the
project is completed as proposed, the 100-year water-surface elevations of
Denton Creek would remain unchanged except at cross section 34850 where an
increase of 0.1 foot would occur. In addition, the 100-year floodplain and
regulatory floodway of Denton Creek would be decreased as indicated in the
submitted floodplain study. Also, if the project is completed as proposed,
the 100-year water-surface elevations of Cottonwood Branch would increase (a
maximum of 0.9 foot) and the 100-year floodplain and regulatory floodway would
be modified as depicted in the submitted floodplain study. It is important to
note that the increase in the 100-year water-surface elevations of DemtolI--.:-: .........
2
Creek and Cottonwood Branch are due to the placement of fill outside of the
regulatory floodway of each stream. Please note that future revisions to the
Flood Insurance Rate Map (FIRM) and Flood Boundary and Floodway Map (FBFM) or
restudies of the flood hazards in this area could modify ~this determination.
~This. determination is based on the 100-year flood discharges computed in the
_preliminary FIS for your community, and does not consider subsequent changes
in watershed characteristics that would tend to increase flood discharges.
~he development of this project and other ~ojects upstream could result in
i'6'6~ased flood ~charges, which, in turn,-~o~'f~--~-~-~'~'-i~"~n-~'~d ~00-year
and-co, Id {her~fore"'~'A~'f~sh' ~fg~"'~'06L~~ood elevations in this area.
This conditional L~R is based on minimum floodplain management criteria
established ~der the NFIP. Your community is res~nsible for approving all
proposed floodplain developments, including the project u~n which this
request is based, and for assuring that necessary ~its required by Federal
or State law have been received. State and community officials, based on
knowledge of local conditions and in the interest of safety, may set higher
standards for const~ction or may limit develo~ent in flo~plain areas. If
the State of ~xas or the City of Coppell has adopted more restrictive or'
c~prehensive floodplain management criteria, ~ese criteria t~e precedence
over the minim~ NFIP requirements.
Please note the requirements for floodway revisions as outlined in NFIP
regulation Part 65.7 (b)(~) (copy enclosed), which states ~at when a floodway
change is proposed, a cop~.~_~..{.p~s notice distributed by ~e community
~tating the comm~it~ intent to revi~""~"~6~way, or a statement by ~e
commun~-%hat it-5~'{~ie~-~'ll affected p~pp~_ ~rs and affected" ~
-'~-~jacent' jurisd~c~i0~ ~'~"-~'--~mitte~ to .tbg.. Federal ~ergency Management
Agency (F~A)-i--~is requirement must'be addressed'~'~e~'~e~ing-'~-ma~ ....
revision to reflect the effects of ~e completed fill project.
We have enclosed a copy of Part 65 of the NFIP re~lations, which further
describes the nature and extent of ~e material needed to sup~rt a request to
revise an effective FIS, FI~, and FBFM. Compliance ~th ~e criteria outlined
in ~is document ~11 expedite F~A's review process, ~us allowing ~e
effective FIS, FI~, and FBFM for your community to ~ revised as appropriate,
in a timely manner.
Should you have any questions regarding this matter, please do not hesitate to
contact the Chief., Natural and Technological Hazards Division of the Federal
Emergency Management Agency in Denton, Texas, at (817) 898-9127 or Matthew B.
Miller of our Headquarters staff in Washington, D.C., at (202) 646-3461.
Sincerely,
Chief, Risk Studies Division
Federal Insurance Administration
Enclosure
cc: Mr. Russell R. 9oyle, P.E.
Mr. Jerry Parche, P.E., Jerry Parche Consulting Engineers
FEDERAL EMERGENCY MANAGEMENT AGENCY
Revised as of October 1, 1986
Amendment No.1, .lune 30, 1987
National Flood Insurance Program
and Related Regulations
Federal Emergenc~ ,anagement Agency § 65.1
PART 65--IDENTIFICATION AND
MAPPING OF SPECZAL HAZARD
ARt. AS
Sec.
65.1 ~-rgose
66.2 Definition.
65.3 Requirement ~o suDm~[ new ~hnic~
65.t Rig~ ~o submit r~ew technical
65.5 Revision to sDecial h~r5 area bound-
~ies wit~ no change ~o b~e 5ood eieva-
:ion dete~ina~io~.
65.6: Re~ion
m~a~io~.
65.7 ~o~w~y revision.
65.8 Review of DroDosed Drojec~.
65.9 Review ~d resDo~e by the A~inis-
t~tor.
~5.!0 ~z~i~ o~ ~e~ protected b~ ~evee
~.I1 ~t o~ co~ities ~ub~itt~ ~~ d~t~
~t~On P~ ~o. ~ o~ I~B; ~.0. i~I~.
4~ ~-3.C. ~I0~ ~utbor~e~ the D~rec- .'
tot ~o identify ~d ~ublish ~o~-
~be ~mted
293
§ 6.~.~ ~1 CFR ~. I (1Q-I-~6
mudslide (i.e.. mudHow) ~d flood-re- [51 ~ 30313. Au~. 25.
l~ted erosion h~ar~. T~e pu~ose of
~is par~ is ~o outline ~he steps ~ corn- ~ ~.l Hi~ht to submit new t~hnical da~
reunite' needs to ~ake in order ~o ~ist (~) A community h~ · ~g~t ~o
~he Agency's effort in providing up-go- quest changes ~o ~' of ~he in/omx-
date identification ~d publication, in gion sho~m on ~n effective ma~ that
the fo~ of ~he maps described in P~ does no~ impact flood plain or ~ood-
64. on special flood, mu~iide (i.e.. way delinea~io~ or b~e flood eleva-
mud~ow) and ~ood-reia~ed erosion tio~. such ~ community boundary-
h~ar~, ch~ges, labeling, or plan/metric
[48 ~ 28278. June 21. 1983] g~ls. Such ~ submi~ion shall include
zppropriate supporting documentation
~ ~5.Z Definitions. in accord~ce w/th ~his part ~d may
(a) Excep~ ~ o~he~ise provided ~ be submitted ~ ~Y time.
~his part. ~he definigio~ se~ fo~h in (b) All reques~ for changes go eff~-
P~rt 59 of ~his subchapter ~e zpDlic~- tire maps. o~her than those
hie ~o this par:. by ~, must be made in writing by
ghe Chief Executive Officer of
(b) For ~he pu~ose of this part, a
certilicztion ~v~. z re~stered profes- cow, unity (CEO) or an official desig-
sional engineer or o~her p~rty does not nated by %he CEO. Shouia the CEO
constitute a warr~ty or ~amcee of refuse to submit such a request on
perfo~nce, expre~ed or implied, behalf of ~nother party. ~MA will
Certification of da~a ~ a stz:emen[ a~ee ~o review i: only if writ:eh evi-
thz~ the dz~a is zccu~te ~o the bes~ of dence is provided indicating ~he CEO
~he certifier's ~owledge. Ce~Hicz~ion or desi~ee h~ been requested ~o
of ~yses is ~ statement ~ha~ :he so.
analyses have been perfomed co~- [51 ~ 3031~. Aug. 25.
iy ~d in zccord~ce with sold engi-
neering practices. Ce~i~:ion of ~ ~.5 ~visio, to s~cial h~ ~ea
st~ctu~i wor~ 5 ~ s~ement that ~undaries with no ch~ge to b~e
the wor~ are desi~ ~ ~cord~ce flo~ elevation determinations.
with sound engin~hng p~ic~ ~o (z) Data re~ir~fortopograpk-
provide protection from ~e b~e ic cA~ges. In m~y ~e~ of speci~
:qood. Ce~ifica~ion of "~ buil~" con~- flood h~d (exclud~g V ~nes ~d
:io~ ~ a s~[emen~ that the floodw~ys) it may be legible ~ eie-
structure(s) h~ been built ~cor~g va~e ~e~ with ez~h 511 ~bove :he'
~ :he pl~ berg ce~i/ied, ~ ~ pl~e, b~e flood elevation. ~ientific ~d
~d ~/uily f~ction~g. :~i~ ~oma:ion ~o su~ ·
[51 ~ 30313, Aug. 25. 1986] quest to ~ excl~ion from ~
ef sp~i~ flood h~d of z st~ct~e
~ ~5.3 ~quirement ~ submit new ~hni- or panel of l~d tha~ h~ ~en elev~:-
~1 ta~ ~ by the pl~emen~ of f~ sh~
A co~unity's b~e 5~d elev~[io~ elude :he foHow~
may ~cre~e or d~re~ r~t~g (1) A copy of the ~o~ed d~ in~-
from physic~ ch~g~ ~f~t~g fl~d- ~t~g ~he leg~ desc~p~ion of ~he
ing condition. ~ s~n ~ p~ti~bie, prope~y ~d the official r~ordation
but not la,er :h~ six mont~ ~r ~fomz~ion (d~d book volme ~d
:he date such ~omztion b~omes page n~ber) ~d bezr~g the se~
available, a co~ity sh~l notify the approD~a~e r~or~ion official
5he A~in~t~or of ~he ~g~ by (e.g.. Count~' Clerk or Recorder of
submitting ~hnic~ or ~ien~ific ~ Dee~).
~ ~cord~ce with th~ p~. Such · (2) If 5he pro~ert~ ~ r~orded on
subregion is n~e~ so thz~ upon plat map. a copy of the r~orded pla~
coniimztion of those physi~ indic~:ing both ~he location of the
changes affecting ~ooding condition, property ~d :he official recordation
hsk premium rotes ~d 5ood plain iniom~:ion (pla: book volme ~d
m~agement requiremen~ will be page number) ~d bearing the seal of
b~ed upon cu~ent dz~ the ~ppropriz~e recordation official.
294
J:edera! Emergenc~ .nagement Agency § 65.5
the property is not recorded on a plat than a single structure or a single lot.
map. copies of the ;ax map or other it must be demonstrated that fill will
suitable maps are required to aid not settle below the elevation of the
FE.~,~[A in accurately '.ocat:ng ..'.he prop- base flood, and char. the fill is
erty. qua~e!y pro~ected from the forces of
(3; If a legally defined parcel of land erosion, scour, or differential sec:le-
is involved, a ~,opographic map indicat- ment a.~ described below:
lng present ground elevations and date (i) Fill must be compacted to 95 per-
of fill. FE,~,i,-k's determination as to cent of the maximum density obtain-
· whether a legally defined parcel Qf able with the Standard Proctor Test
la,nd Is to b- excluded from the area of method issued by the A_merican Socie-
sl~ecial flood hazard shall be based ty for Testing and Materials (AST..~
upon a comparison of the ground e!e- Standard D-698). This requirement
rations of ~he parcel with the eleva- applies to fill pad~ prepared for resi-
:ions of .the base flood. If .the ground dentiai or commercial structure foun-
elevations of r-he entire legally defined dations and does not apply to filled
parcel of !and are ar. or above the cie- area~ intended for other uses.
rations of the base flood. ;he parcel (ii) Fill slopes for granular materials
may be excluded from ;he .~rea of $1~e- are not steeper than one vertical on
cia! flood hazard, one-and-one-half horizontal unless
(4~ If a str~lcture is involved, a tol~o- substantiating data justifying steeper
graphic map indica.'-ing structure ioca- slopes is submitted.
~ion and ground elevations including (iii) Adequate protection is provided
:he elevations of the lowest floor (in- fill slopes ext~osed to flood waters 'with
cluding b~sement) and r-he lowest ad- expected ve!ocities during the occur-
jacent grade to the structure. FE~%'s fence of the base flood of five feet per
determination as to whether a struc- second or less by covering them with
ture is to be excluded from the area of grass, vines, weeds, or similar vegeta-
sI~eciai flood hsz,mrd shall be based tion under=~rowth.
ul:on a comparison of the elevation of (iv) Adequate protection is provided
the lowest floor (including basement) fid slopes exposed to flood waters with
and the elevation of the lowest adja- velocities during the occurrence of the
cent grade with the elevation of the base flood of greater th~n five feet per
ba~e f!ood. If the entire structure and second by-a.-rnoring them with stone
the lowest adjacent grade are at or or rock slope protection.
alcove the elevation of the base flood, (7) A revision of flood plain delinea-
:he structure may be excluded from tions based on fill must demor,~tra:e
the area of sl~eciai flood hazard. ~hat any such fill has not resulted in
(5) Data to substantiate the base floodway encroachment.
flood elevation. If I:'EIVIA has complet- (b) Ne~ topo!rrapAic gat~. The pro-
ed a Flood Insurance Study (FIS). cedures described in pmm~raphs
that data will be used to substantiate through (5) of this section may be
the base flood. Otherwise, data provid- foilowed ~ reques~ ~ m~p revision
ed by an authofitat, ive source, such ~ when no physical changes h~ve oc-
the U.S. Army Cor~s of Engineers, cuffed in the area of special flood
U.S. Geological Survey. U.S. Soil Con- hazard, when no fill has been placed.
se.~;ation Se.~'ice. state and local water and when the natural ~'ound cloys-
resource departments, or tec.hnicai tions, as evidenced by new topographic
data prepared ~nd certified by a regis- maps. more detailed or more accurate
:ered professional engineer may be tha~ those used to prepare the mai)
submit:ed. If base flood elevations be revi~ed, are shown ;o be above the
have not previously been e~tabiished, elevation of the base flood.
hydraulic caJculatiorm may ~iso be re- (c) Certi/icatio~ requirement. The
quested, iterm~ required in l~aragr~phs (a) (3)
i6) '~Vhere fill has been placed to and (4) and (b) of ~his section shall be
raise the ground surface to or above certified by a registered professional
~he base flood elevation ~nd the re- engineer or licensed land surveyor.
quest to gain exclusion from an area Iterm~ required in paragraph (a)(6) of
of spec/al flood hazard includes more this section shall be certified by the
295
§ 65.6 44 ~J:K Ch. I ( 10-1-86 Edition)
community's N'FI1~ permit official, a be accepted. ~ny computer ~rograrn
reg~tered 9rofe~ional engineer, or ~ ~ed m~t be ~ce;ted for gene~l use
~credited soih engineer. Such certifi- by a gove~ental agency or notable
eatio~ ~e subject to the ;rovisio~ of scientific body. must be well docu-
f 65.2 of th~ subcha;ter, merited including a ~er's ~d 9to-
(d) Summation procedures. ~1 re- ~mer's m~ual. ~d must be avail-
ques~ s~all be submitted :o the a~ro- able to the ~enersl user.
p~a:e ~ Regional Office se~icing (7) A revised hydrologic ~alysis for
the community's ~eo~aphic ~ea. floodin~ sourc~ with established
[51 ~ 30312. Au~. 25. 1986] flood eleva:io~ must include evalua-
tion of the s~e recu~ence inte~al(s)
~ 6~.6 ~vision of b~e flood eieva~io, de- studied in the eff~tive ~S. such
terminations, the 10-. 50-. I00-. ~nd 500-year flood
(~) ~ewal co~ditio~ ~nd d~ta re- discharges.
qui~ement~. (1) The suppor~in~ data /8) A revised hy~aulic ~lysis for
m~t include all the info~a:ion fioodin~ source with established
~ nee~ ~o review ~d evaluate flood elevations must include evalua-
tion of the s~e recurrence inte~ai(s)
the request. This may involve the
questor's performin~ new hydrologic studied in the effective FIS. such
~d hydraulic an~iysis and delineation the 10-. 50-. i00-. and 500-year flood
of new flood plain boundaries ~d eleva:ioP~, and of the floodway. Unle~
floodways. ~ nece~ary, the b~is of the reques~ is the use of
(2) To avoid discontinuities between ~ ~te~a:ive hydraulic methodology
the revised ~nd unrevised flood data. or the requestor c~ demonstrate
the nece~y hydrologic ~d hydrau- the da~a of the o~inal hydraulic com-
1lc ~yses submitted by the map re- purer model ~ unav~l~ble or its use is
vision requestor m~t be exte~ive ~approp~ate. the ~ysis sh~l be
enough to e~ure tha~ · lo~c~1 frei- made ~inE the s~e hyd~ulic com-
tion can be shown between the revised · purer model ~ed to develop the
flood elevation, flood plan bo~d- flood elevations sho~ on the eifec-
~ies. ~d floodways ~d those devet- rive ~ood Insu~ce ~te .~p ~d
oped previo~ly for ~e~ not ~f~ted updated to show present conditions in
by the revision. Unie~ it is demon- the flood plan. Copies of the input
stated that it would not be appropri- ~d output da~a from the ori~in~ and
· te. the revised ~d unrevMed b~e ~vised hyd~ulic ~aiys~ shall be
flood elev~tio~ m~t match with~ submitted.
one-h~i foot where such t~itio~ (9) A hy~oio~c or hy~ulic ~-
occur, sm for · flooding source without estab-
(3) ~e~sio~ c~not be made b~ed l~hed b~e flood elevatio~ may be
on the effec~ of proposed projec~ or ~rfo~ed for o~y the 100-ye~ flood.
future condit!o~. Section 65.8 of th~ (10) A revision of flood plain delinea-
.subchapter con~ prov~io~ for ob- tio~ b~ed on topo~aphic ch~es
t~nin~ condition~ ~pprov~ of pro- m~t demo~t~e that ~y topo~ph-
posed proj~ t~t may eff~t m~p ic ch~ h~ve not ~sulted in
ch~ when they ~e complete, floodway encro~hment.
(4) ~e ~t~ ~d d~te of relevelin~ (11) Delinestio~ of flood plain
of benc~~, if ~y. :o which the boodles for a floodin~ source with
elev~io~ are refe~nc~ m~t be ~di- es~blish~ b~e flood e!evatio~ must
~ted. p~vide both the 100- ~d 500-year
(5) M~ps will not be revised when flood pl~ bound~es. For floodin~
d~ch~Ees ch~Ee ~ a result of the souses without establMhed b~e flood
~e of ~ ~tem~tive methodology or elevations, o~y 100-year flood plain
data for computin~ flood disch~es bound~es need be submitted. These
unle~ the ch~e ~ star,richly siE- boodles should be shown on ~ topo-
nific~t ~ me~ured by a confidence ~phic m~p of suitable scale ~d con-
limi~ ~ys~ of the new discharge es- tour inte~al.
timates. (b) Data re~uir~e~!~ for co~ec!in~
~6) In order for an ~te~a:ive by- map e~. To correct errors in the
d~ulic or hydrologic methodology to ori~in~ flood ~alysis. technical data
296
· l=ederai Emergency 2nagernent Agency § 6:5.7
submissions shall include the follow- hydrologic, hydraulic, or topographic
lng: data shall include the following data:
(i,' Data identifying mathematical {1; Da~,a that are believed to be
errors, better than t,hose used in the or:ginal
{2) Data identifying measurement analysis ~such am additionai years of
errors and providing correct measure- stream gage data).
ments. ¢2) Documentauon of the source of
(c) Da~a requirements for changed the data.
pavsical condilion$. Revisions ba~ed ~3) Explanat;on as to why the use of
on the effect~ of physical changes that the new data wi1! improve she results
have occurred in the flood plain sh~l of the origin~l ~nalysis.
include: (4) Revised hydrologic ~alysis
(1) ~nges a//ecting h~droio~c con- where hydrologic d~:~ are being incor-
gitions. The following ds~ must be ~ors~ed.
submitted: (5) Revised hydraulic analysis ~d
(i} Oeneral description of ~he ~ood elevauon profiles where new by-
changes (e.g.. d~. diversion chapel, drologic or hydraulic data are being
or detenuon b~in}, incorporated.
iii) Co~truction plans for ~-built (6) Revised deiineatio~ of the flood
conditior~, if applicable, plain boundaries and floodway where
(iii) New hydrologic ~nalysis ac- new hydrologic, hydraulic, or topo-
counting for the effect~ of the graphic data are being incorpo~ed.
ch~ges. (et, Data requireme~ /or inco~o-
(iv) New hydrz~ic ~alysis ~nd pro- rating improved ~e!ho~. Reques~
files ~ing the new 5ood discharge for revisio~ b~ed on the ~e of im-
v~ues r~ulting from ghe hydrologic proved hydrolo~c or hyd~ulic me~h-
~ys~. odoiogy shall include :he following
(v) Revved de!~eatio~ of the flood da~:
~l~in bound~es ~d 5oodway. (1) New hydrologic ~alys~ when an
(2) ~anges a~fecting hvdrauiic con- ~temative hydrologic methodology is
ditio~. The following da~ sh~ be being proposed.
submitted: (2) New hyd~ulic ~aiysis and ~ood
(i) Oene~ desc~Dtion of the elevation profiles when ~ ~:emative
ch~ges (e.g., ch~nel~tion or new hyrologic or hyd~ulic methodology is
b~dge, culve~, or levee), being ~roDosed.
(ii) Co~t~uction DI~ for ~-built (3) Expiration ~ ~o why ~he ~lter-:
condition, native methodoio~es
(iii) New hyd~ulic ~alys~ ~d ~he origin~ methodologies.
flood elevation profiles a~ounting for (4) ~e=~ed delineatio~ of the 5ood
the effec~ of the ch~ges ~d ~ing plain bound~es ~d 5oodway b~ed
~he o~ flood d~charge v~ues on :he new
upon which :he o~gln~ m~p ~ b~ed. (f) Certification ~q~ir~. Ail
(iv) Re~ed deline~tio~ of ~he Dood ~ysis ~d d~:z submitted by the re-
quester sha~ be certifi~ by a regis-
plain boodles ~d 5oodwmy. tered professional eng~eer or lice~ed
(3) ~anges invoiL~ng topographic l~d su~/eyor, ~ approp~ate, subject
condition. ~e following da~a shall
to the definition of "ce~ifica~ion"
be submitte~ ~ven at ~ 65.2 of this subchapter.
(i) Gene~' desc~tion of the
ch~ges (e.g., ~d~g or fi~ing), ques~ sh~l be submitted to the a~ro-
(ii) New :o~o~hic ~o~a:ion. p~ate ~A Re~onal Office se~icing
such ~ s~o~ elevation, cross sections the community's geographic ~ea.
~ding ~1~, or contour ma~s.
(iii) Revmed del~eations of the flood
plain boundaries ~d, if nece~ary.
floodway. ~ f5.7 Floodway re-isions.
id) Dat~ req~ir~en~ for i~co~o- (a) General. ~oodway data is deve!-
~ting immured datm Reques~ for re- oped ~ part of ~MA ~ood I~mur-
~io~ b~ed on the ~e of improved ~ce Studies and is util~ed by comau-
297
~§ 65.~ 44 C~:. ~h. ! (10-1-86 ~:diti~n)
nities to select a.nd adopt floodways a~ tion c,~an~es. The followin~ d~a shall
part of ~he flood plan m~agemen: be submit:ed;
pro~ required by f 60.3 of this sub- (1) I~ems described in para~phs
chapter. When it h~ been determined (1) through ~3) of chis section must be
by ~ community that no p~cticable al- submitted.
terna~ives exist ~o revising the bound- (2) Engineering ~alysis for ~he re-
~ries of its prev~o~iy adopted Good- vised Goodway, ~ described be!ow:
way, the procedures below shah be foi- (i) The original hyd~ulic computer
lowed, model used to develop the established
(b) D~ta requir~Z~ ~he~ 5~e b~e ~ood elevations m~t be modified
floo~ eie~aiion cA~nges ~re req~e~te& ~o include ~11 encroachmen~
When · floodway ~vision is requested have occurred in the 5ood Dlain since
in ~ocia:ion with · ch~ge to b~e :he existing ~oodw~y w~ develoDed.
5ood elevation. :he da~a require- If :he original hy~ulic comDuter
men~ of ~ 65.5 sh~l ~so be ~Dlic~- model is no~ ~vailzble. ~ ~:e~a:e ~y-
bio. ~ ~ddition. ~he following docu- d~uiic comDu:er model m~y be
mentation shall be submitted: Drovided the ~lte~z[e model h~ been
(I) Co~y of a ~ublic no~ice dis~ribut- calibrated so ~ ~o reDroduce ~he or~gi-
ed by the communi[y sta~ing %he corn- nal wa:er surface Drofile of ~he origi-
munity's in~en: :o repine the 5oodw~y na! hydraulic comDu:er model. The ~i-
or · statement by ~he co--unity ~ha: ternz~e model must be then modified
it h~ notified M1 affected ~roDerty to include ~i1 encroachments
owne~ ~d ~fected ~djacen: jurisdic- have occurred since :he exmting flood-
tio~. way %-~ developed.
(ii) The floodway ~ys~ must be
(2) Copy of · let:er notifying the ~p-
propriate State agency of the flood- perfo~ed wi[h the modified compu~-
way revision when the S~te h~ juP~- er model using the desired 5oodway
diction over :he ~oodway or i~ adop- 1~i~.
tion by co--unities p~icipa[ing ~ (iii) The ~oodway limi~ mus[ be se[
the ~I~. so tha~ combined eff~ of the
(3) Documentation of the approval encro~hmen~ ~d the new floodway
l~i~ do no~ incre~e the effective
of the revised floodway by the ~ppro-
p~ate S~te agency (for communities b~e flood elevatio~ by more than the
~o~: s~ecified in ~ 60.3(d)(2).
where ~he State h~ ju~iction over
~he floodway or i~ ~o~tion by corn- Copies of ~he in,ut ~d out,ut
muni:ies pa~ici~atmg ~ :he ~IP). from :he o~n~ ~d modified corn-
(4) ~ginee~mg ~ys~ for :he re- ~u~er models m~t be submitted.
vised floodway, ~ de~b~ below: (3) Delineation of the ~ed Mood~
(i) The floodway ~~ m~t be way on a co~y of the off, rive
perfo~ed ~ing the hy~ulic corn- map ~d a suitable topo~hic map.
purer model ~ed to dete~ine ~he (d) Certification re~i~~. All
~yses submitted shmH be codified
proposed b~e flood elevm~io~, by · re~stered prof~ion~ on,neet.
(ii) ~e floodwmy 1~i~ m~t be se~ ~ ~po~hic data sh~ be certified
~ that neither ~he eff~tive b~e flood
elevm~io~ nor ~he pro~o~d b~e flood by a roistered p~f~ion~ engineer
or lice~ed i~d s~eyor. Certifica-
elevmtio~ ~ le~ th~ ~e off, rive ~io~ ~e subject ~ the def~ition
b~e- flood elevm~io~. ~e ~cre~ed by ~ven a: i 65.2 of :bm su~haster.
more th~ the ~o~ s~ified ~der (e) S~bm~ion p~cedu~s..~1 ~e-
~ 60.3 (d)(2). Copies of the ~pu~ ~d
output ~ f~m ~e o~ ~d ques~ tha~ involve ch~ges to 5ood-
ways sh~l be submi~t~ to the ~ppro-
modifi~ ~mvu~r m~e~ m~: be p~e ~ Region~ Office se~cmg
sub~tt~. ~he ~uni~y's g~p~c
(5) Del~e~ion of the ~ flood-
way on the ~e to~hic m~v [51 ~30315, Aug~. 19861
~ed for the del~eztion of the ~v~ed
flood bo~d~. ~ 63.~ ~view of p~s~ ~j~.
lc) Data ~qui~~ for ~an~es A co--unity, or individu~ through
not ~so~a~g ~ ~e ~oo~ elev~- the co--unity, wishing ~'s com-
298
.- Pedera! Emergency znagement Agency § 65.10
ment~ on whether a proposed project, flood hazard and risk mapping effort
if built ~ proposed, ~ou]d ]~ti/y · ~hose levee syste~ thz~ meet, and
map revision may request · Condition- continue to meet. minimum desi~.
al Letter of M~p ,~mendment or ~ev~- e~ion. ~d mainten~ce standards
sion in ~ccord~nce with P~rt 72 of ~his ~b~t ire consistent with ~he level
subch~pter. The d~t~ required ~o sup- protection sough~ ~hrough ~he ~o~-
port suc~ reques~ are ~he s~e ~ prehensive :7ood p~ain
those required to support requests for criteria established by ~ ~0.3 of
revisioms in ~¢¢ordance ~itln ~ 6~.5. subchapter. Ac~ordin¢!y. ~his ~ectlon
65.6, and 65.7, except ~-built ¢ertifica- describes the ~ypes of information
~ion ~ no~ required. ~,{ needs to reco~ize, on
[51 ~ 30~1S. Au¢. ~5, 1986] maps. ~hzt a levee system provides
pro~.ection from ~he b~e flood. This
~ 6S.9 Revie~ and response by the Adm~n- information must be supplied
ist~or. ~M.{ by ~he community or other
if ~ny questio~ or problems ar~se par~y seekin¢ recocnJ~ion of such
levee system a~ ~he ~ime a flood risk
durin¢ review, ~f,{ ~iI consult ~he study or restudy is ~onduc~ed. '~'hen
Chief Executive Officer of ~he co,mu- map revision under :he pro,.'is~ons
nity (CEO). the community official P~rt 65 of Lhis subchap~er is souch~
desi~ated by ~he CEO. and/or ~he re- b~ed on a levee system, and upon
quester for resoiution. L'pon receipt of
ques~ by ~he .{dminis~ra:o~ dur!n~
~ revision request, the Administrator review of previously recocn~zed
shail m~il ~ ~c~no~ied~en~ of
tures. The ~,f,{ review '~'ill be for
¢eipt of such request to the CEO. ~he sole purpose of estabhsh!n¢ appro-
W~hin 90 days of receivin¢ ~he re- pria~e r~k zone dete~ina~ions for
quest with ~ll nece~ry ~/o~tion. N~IP maps ~d shall not constitute
the A~inist~tor shail notify the dete~ina~ion by ~M.~ ~ ~o how
CEO of one or more of the follo~n¢: structure or system will perfor~ ~n
(~) The effective m~p(s) shall not be
flood event.
modified; (b) Des{g~ c~ For levees ~o be
(b) ~e b~e flood elevatio~ on the
effective ~M sh~! be modified ~d reco~ed by ~MA, evidence tha~
~dequa~e desi~ ~d opera~ion and
ne~ b~e flood elevatio~ shall be es- maintenance systems ~e in place ~o
~blBhed under the prov~io~ of P~t
provide re~onable ~u~ce that pro-
67 of this subch~pte~ tection from {he b~e ~ood exis:s..
(c) ~e changes requested ~re ~p- mus~ be provided. The foilo~im~
proved ~d the m~p(s) ~ended by quire~en~ must be met:
~tter of ~lzp ~ev~ion (LOMb); (1) Fre¢~o~ (i) ~iverine levees
(d) The threes requested ~re ~p- must provide a min~um freeboard of
proved ~d · revved m~p(s) ~ill be
three feet ~bove the w~ter-surface
printed ~d dist~buted; level of the b~e flood. An ~ddition~l
(e) The ch~nKes requested ~e not of
one foot above the minimum is re-
such · si~ific~t n~ture ~ t~
~ ~i~u~ce or rev~ion of the flood in- quired ~ithin i00 f~t ~ either side
st~ctures (such ~ bridces} Nve~'~rd
su~ce study or m~ps ~d ~ill be de-
of ~he levee or ~herever the flow
feted ~til such time ~ · si~ific~t co~tricted. An ~dditionai one-half
choke occum: foot ~bove the minimum ~ :he up-
(f) .~ ~ddition~ 90 d~ys ~ required
stre~ end of the levee, tzperin¢-
. to ev~u~te the ~ientific or technic~
not le~ th~ the m~imum ~t the
~ sub~tted; or do~tre~ end of the levee. ~ ~o
(E) Ad~tion~ d~ ~e required ~o
required.
suppo~ ~he ~v~ion request. (ii) Occ~ion~ly. exceptio~ to the
[51 ~ 30315. Au~. 25. 1986] minimum ~verine freehold require-
men: described in p~a~ph (b)(1)(i)
~ 6~.10 ~agpin~ of ~e~ prorated by ol ~his sec:ion, may be approved. Ap-
levee systems, propriate en~ineerin~ ~yses demon-
(a) ~ne~ For pu~oses ol ~he s~r~in~ adequate protec:ion wi:h
~P, ~ ~11 o~y reco~ize in i~ le~er freeboard taus: be submit:ed
299
§ 65.10 44 C~:R Ch. I (10-1-86 Editian}
support a request for such an excep- include, but are not limited to: Expect-
~ion. The material presented must ed flow velocities (especially in con-
evaluate the uncertsinty in :he esti- str/c:ed ~re~): expected wind ~nd
mated b~e flood elevation profile ~nd w~ve ~crion: ice loading; impact of
include, but not necesszr!iy be limited debris; slope protection techniques;
to an ~sessment of s~acisucai confi- duration of flooding a~ various stages
~ence limits of the iO0-year ~ischarge: and velocities: emb~kment and foun-
changes in s~age-discharge re!acion- da~ion ma~eria{s; levee alignment.
sh~s; and the sources. ~o~ent:~l. ~nd bends. ~d traditions; ~nd levee side
magnitude of debris, sediment. ~nd ice slopes.
accumulation. It mus~ be ~iso s~own (4) Embankm~t an~ foundation
~ha: ~he levee will remain struc~ur~lly stability. Engineering ~alyses that
stable during the b~e flood when evaluate levee emban~en~ s~abili~y
such additional loading considerations must be submit:ed. The analyses pro-
are imposed. Lrnder no circumstances vided shall evaluate expected seepage
will freeboar~ of !ess %k~n two feet be during loading conditions ~sociz[ed
~cceDted. with the b~e ~ood and shall demon-
(iii~ For coastal levees. :he freeooard
stra[e that seepage into or through
taus1 be es:aolished at one foot above ~he levee foundation and emDankmen[
the height of the one percent wave or
w,~. not jecpardize embankment
the maximum wave runup whichever foundation stability. An alternative
is grea~er~ ~socizfed '&'~th the 100- analysis demonstrating that the levee
year sti!lw~ter surge eievacion at the is designed and constrt~cted for stzbili-
si~e.
,~iv) Occ~ionai!y, exce~lons ~o ~he :y against loading conditions for C~e
IV ~ defined in ~he U.S. A~y Cor~s
minimum co~:al levee freeboard re- of Enginee~ (tOE) m~nu~l. "Desi~
quirement described in ~ar~gr~h ~nd Co~t~ction of Levees"
(b)( !)(iii) of ~his sec:ion, m~y be ~-
~roved. A~ro~rla~e engineering ~nal- 1110-2-1913. Cha~er 5. Section
yses demonstrating ~dequa~e ~ro~ec- m~y be used. The fac~o~ th~ sh~ll be
~ion with ~ lesser freeboard must be addressed in ~he ~nalyses include:
submitted :o su~ort · reques~ for De~h of ~ood~g. duration of flood-
such ~n exception. The mate~l ~re- lng. emb~ment geometry ~d len~h
sente~ must ev~ua~e ~he uncer:ain~y of seepage ~th ~t c~tical locations.
in ~he estimated b~e Pood !o~ding emb~ent ~d fo~da:ion materi-
· is. emb~ent compaction. ~enetr~-
condition. P~ticular em~h~is must
be ~l~ced on :he effects of w~e ~t~ck tions, other desi~ f~cto~ ~fecting
~d overtopping on :he stability of the seepage (such ~ d~in~ge l~ye~), ~nd
Ievee. Under no circu~t~ces, howev- other desi~ f~to~ ~fecting ear.k-
er, will ~ freeboard of less th~ tw~ men~ ~d foundation s~ability (such
feet ~bove ~he 100-year ~tillw~ter be~).
surge elevation be ~cce~ted. (5) ~et~L Engineering ~yses
(2~ ~o~res..~1 o~enin~ m~: be m~t be sub~tted ~ha: ~e~ the ~o-
provided with closure devices th~: ~e :enti~ ~d ma~itude of fur. ute lo.es
st~ctu~l ~ts of the system du~ng of freehold ~ ~.resul~ of levee settle-
o~e~tion ~d desi~ ~ccording ~o ment ~d demo~t~e thz: freeboard
sound enginee~ng ~ctice. - will be m~n~ed within the mmi-
~3) Emba~ment ~roteclion. Engi- mum st~d~ set forth in ~mgr~h
nee~ng ~yses must be submitted (b)(1) of this s~tion. Th~ ~lysis
:hat demonstrate that no a~reci~5le m~t ~ddr~ emb~ent Ioa~. corn-
erosion of the levee emb~men~ c~ ~re~ibility of emb~ent soil. com-
be exacted during the b~e flood. ~ ~ ~ressibility of foundation so/h. ~ge of
result of either curren~ ~r w~ves. ~nd ~he levee system. ~d co~t~ction
:ha: ~tici~a~ed erosion will not result com~ction method. ~ ~ddition. de-
in f~ilure of ~he levee embankmen~ or ~iled settlement ~Iysis using ~roce-
founds:ion directly or indirectly dures such ~ :hose desc~bed in the
through reduction of ~he seepage ~h COE manual. "Soil Mechanics
· nd subsequent instability. The f~c- Desi~Settlement Analysis"
:o~ ~o be ~ddre~ed in such ~lyses 1100-2-190~) must be submitted.
300
Federal Emergency / ~agement Agency § 6:5.10
(6) £n~cr~or dr~i~,,ge. ~ ~ys~ (iii) ~ovisions for periodic o~e~-
m~t be submitted th~ identifies the ation. ~t not le~ than one-year inter-
source(s) of such flooding, the extent vals, of the closure structure for test-
of the flooded ~e~ ~d. ii the avenge lng ~d training pu~oses.
de~th ~ ~e~er th~ one foot, :he (2) [nte~or ~rainage s~ste~. Interl-
wa~er-surf~ce elevationts) of the b~e or d~in~ge systems ~ociated with
flood. Thi~ ~alysis m~t be b~ed on levee systems usually include storage
the joint probability of interior ~d are~. ~avity outlets, pumping
exte~or ~ood~g ~d the capacity of tions, or a combination thereof. These
f~cilities (such ~ drainage lines ~d drainage syste~ will be reco~ized by
p~ps) for ev~ua~ing interior flood- ~ on NFtP maps for flood protec-
water, tion p~poses only if the following
(7) O~ew ~si~ c~te~ In ~ique minimum c~teri~ ~e inciuded in
situation, such ~ those where the ope~tion
levee system h~ relatively high ~1- (i) Documentation of the flood wa~-
nerabili~y. ~ may require that lng system, under the jurisdiction of
other desi~ crite~a ~d ~alyses be Federal. State. or con, unity
submitted to show that the levees pro- that will be used ~o trigger emergency
vide adequate protection. ~ such situ- operation activities and demonstration
a~io~, sound en~neermg p~ctice will that sufficient flood warning time
be the stand~d on which ~ will exis~ to pe~it activation of mecha-
b~e i~ deteminatio~. ~A will nized portions of the drainage system.
a~o provide the rationale for requir- iii) A focal pi~n of operation
~g this ~ddition~ infoma~ion, cluding s~ec!fic actions and ~si~-
(c) Opemtion pla~ and c~te~ For men~ of res~o~ibility by individual
~ lev~ system to be r~o~ed, the n~e or title.
ope~:ion~ c~te~ m~t be ~ de- (iii) ~ovision for m~u~ backup for
~bed below. ~1 closure devices or the activation of automatic systems.
m~h~i~ syste~ for ~te~ ~n- (iv) ~ov~io~ for periodic ~pec-
~e. whether m~u~ or automatic, tion of ~terior ~inage syste~ ~d
m~t be ope~ ~ ~cor~ce with periodic ope~tion of ~y mech~ed
~ offici~y ~dopted o~e~tion por~io~ for testLng ~d training pur-
m~u~. · copy of which m~t ~ pro- poses. No more th~ one ye~ shall
~d~ ~ ~ by the ope~tor ~hen e!~pse between either the ir~p~tioP~
lev~ or ~~e system r~o~ion ~ or the overflow.
berg ~ught or when the m~ for (3) O~ew opemtion pla~ ang c~le-
~ ~re~o~ly ~o~ed system ~ re- ~ Other ope~ting pl~ ~d criteri~
~ed ~ ~y m~er. ~ ope~tio~ may be required by ~ to e~ure
m~t be ~der the j~ction of · th~ ~dequ~te proration is provided in
P~e~ or S~ ~ency, ~ ~ency sp~ffic situation. ~ such c~es.
cre~t~ by Fede~ or S~e law. or ~ sold emergency m~gement p~c-
~ency of · community p~icipaC~ rice ~ be the s~d~d upon which
~ the ~. ~ dete~a~io~ will be b~ed.
(1) ~u~ Open,on pl~ for ~ (d) ~int~ance pl~ a~g
s~ m~t ~clude the follow~c For levee syste~ to be reco~ed
(i) Docmen~tion of ~e flood w~- provid~g proration from the b~e
~g system, ~der the j~c~on of flood, the m~ten~ce c~teria
PedeX. S~te, or community of[ici~, be ~ desc~bed hereto. Levee systems
that ~ ~ ~ ~ ~gger eme~ency m~t be m~mtmned ~ accord~ce
ope~on ~viti~ ~d demolition ~th ~ offici~y ~dopted mainte-
~ s~ficient flood w~ t~e n~ce pl~. ~d · co~y of th~ pl~
ex~ for the completed open,on of m~t be p~ded to ~ by the
~1 clos~e st~ct~es, ~clud~g n~es- o~er of the levee system when r~o~-
~ se~g. before floodwate~ ~h nition M being sought or when the
the b~e of the clos~e, pl~ for a previo~ly reco~ed
iii) A fo~ pl~ of ope~:ion in- system M revved in ~y m~er.
ctuding sp~ffic ~tio~ ~d ~i~- m~ten~ce activities m~t be under
men~ of respo~ibility by ~di~dual the ju~diction of · Feder~l or State
n~e or title. ~e~cy, ~ agency created by Peder~
301
§ 65.11 44 CFR Ch. ! (10-1-86 ~.dition)
or State law. or an agency of a commu-
nity participating in the NF!I= that
must assume ultimate responsibility
for maintenance. This pla~ must docu-
ment the formal procedure that en-
sures that the stability, height, and
overall integrity of the levee and
associated structures and systems are
maintained. At a minimum, mainte-
nance plans shall specify the mainte-
nance activities to be performed, the
frequency of their performance, and
the person by name or title responsi-
ble for their performance.
(e) Certi£ic-_tion re~u~re.~ents. Data
submitted to support that a given
levee system complies with the struc-
tural requirements set forth ,in par~_-
graphs (b)~l) tlnrough (?) of ~his sec-
tion must be certified by a registered
professional engineer. Also, cerzified
a.s-buiit plans of the levee must be sub-
mitted. Certifications are subject to
~he definition given at § 65.2 of this
subchapter. In lieu of these structural
requirements, a Federal agency with
responsibility for levee design may cer-
tify that the levee has been adequate-
ly designed and constructed to provide
protection against the base flood.
[51 FI~ 30316. Aug. 2§. 19861
§ 6.5.11 List of communities submitting new technical data.
This section provides a cumulative
list of communities where modifica-
tions of the base flood elevation deter-
minations ,~ave been made because of
submission of new scientific or techni-
cal data. Due to the need for expedit-
mg the modificatior~, the revi~ed rrmp
is already in effect and the appe~i
period commences on or about the ef-
fective date of the modified mat~.
interim r~.,le, followed by a final rule,
will list ~he revised map effective date.
local repository and the na~ne a~d
dress of the Chief Executive Officer of
the community. The rn~p(s) is (aze) ef-
fective for both flood plain manage-
ment a.nd insurance purl~oses.
[51 P~ 30317. Aug. 25. 1986]
~-~DI.TO~IAL .~OTK: ~'or I~ !i~t of communities
i~ued under thL~ section ~d not c~-ried in
the CFR. see tl~e List of CI=R Sectior~ Af-
fected ~DDe~ring in the Finding Aids section
of tl~i~ volume.
302