FLOOD05152

• County: Arapahoe
• Community: Arapahoe County
• Stream Name: Cottonwood Creek
• Basin: South Platte
• Title: Request for Letter of Map Revision
• Date: 2/1/1990
• Prepared For: FISMA, Inc
• Prepared By: Greenhorne & O'Mara, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

101.. w..r.. un.bl.. to run . calibration run b....d on pr..vious studi... for
Cottonwood Creek sine.. th.. original FH....D and FIS HEC.2's could nOt be

locat..d.

II.. did perfotlll a calibration run on anotb..r creek in theD..nver

!!etropolitan ar..a to d....onstrate consistent ,"od..l (!IEC_2) output.
attached HEC_2 and summary tables for "Calibration'.

S....th..

VI. !'LOODIiAY

As part of this n.." study, a floodvay wu d..t..tllIin..d b....d on a luxi..\1lD
allowable .urcharge of O.S het per new Arspahoe County regubtlons. (Note
that the 1969 FlS used a 1.0 surcharge). We have prepared snd enclosed.
floodw.y O.t. Table.

In addition, we nn a HEC.2 reHecting proposed development for Little

People's Landing.

Th.. following tabl.. summarizes tbe "ater surf see
that the allow.ble surchar>:e through tbis reach exceeds

elevations.

Not..

the surcharge from th.. proposed development.

~~
.0
o
~8
~~
80
,,~
8

Profile. hsve bee" prepared usi"g twO differ..nt $cales.

One profile show.

only the 100_yeat
the scale of the

Hoodsndusesa'tertical acaleofl"-20..

Thi.matches

profiles 1" the 1989 FlS fnr t.hh portio" of Cottonwood

Creek. ^ second profil.. wa. prepare<l showing the .La-year, ~O-year, .LOO_
year. a"d SOO_year profiles using a vertical scale of l' ~ 5'. Thi. scale
mstches the scale "f the l"werportionofCottonwoodCreek,,,hich iscurreotly
a "detailed study".

VII. PROPOSED DnrELOPKENT

A Pr..li~inary Overlot Grading Plan and cross_sections have been prepared a"d
.ub~itted fer tbe develop~eot of Little People'S Landing. At the co,"pletien
of construction "as-constructed" cross_sections will be surveyed to insure
c"nfo<~ance ~ith this CLO~R and .ub~itted to FEMh .s a LOMR.

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