FLOOD08822

• County: El Paso
• Community: Colorado Springs
• Stream Name: Sand Creek
• Basin: Arkansas
• Title: Flood Hazard Analyses
• Date: 7/1/1973
• Prepared For: Colorado Springs, El Paso County
• Prepared By: USDA Soil Conservation Service
• Floodplain - Doc Type: Floodplain Report/Masterplan

-15-

-16_

P~ojected CQ~dLtiQ~

been prepared singularly or em a pIat by plat basis. Locations of potential
flooding by various frequency storms on the major channels of Sand Creek
were not known until this flood hazard analyses was completed. The analyses
can be used in developing a master drainaJl;e plan for the entire Sand C reck
watershed.

At the ti~c this study ~aS made, it was not possible to predict the
location Or dimensions of road cros5ings or channel modifications which
will occUr in the future. All of these changes ,.-ill have a si.gnificant
~ffect on the potential flood lin~ elevations and locations. For this
rcason the study for projected conditions inClude only tho effects of
additional runoff based on a change of land use expected by the year 199~.
TIle additional runoff was routed through the stream channels and fl cod
plains using existing topographic conditions. Incompa.ringthcresu1tsof
the study, existing conditions with projected conditions, the two analyses
showverylittlediffereneeinpotentialflcodlineelevations. Inmany
instances, the elevation change amounts to lesS than One foot. The 5igni-
ficanC<J of this change in terms of hazard is d~pendent upon future flood
plainu,candthe location of futurc developITIcnts.

Primary purpose of this report is to provide maps of the flood hazard
areas so that local governments ellndevdop floodplain regulations. Flood
plain resolutions were passed by the El Paso County Board of County Commissioners
on February 8, 1973. Colorado Statutes (page 2) require approval of flood
zone regulations by the COlorado l\.ater Conservation Board. ThelOO-yearflood
line delineation should be useful when application is made for approval of
flood zone regulations.

Fa.c.!:JJI!", Atltlec-tbtg FeoucU.ng

Exhitit B is a selection of typical valley cross-sections illustrating
the configuration of the stream channels and adjoir.ing flood pl~in area,.
The SO-, 100-, and SOO-year flood lines are shown ~'ith a notation of ch.va-
tion differential between existing and projected runoff conditions. Table 1.
Flood Plain Reference Data, inCludes flood line elevations for the 100_ and
50tl-yearfIoods under existing and projected runoff conditions for each croSS-
5ection in the study area.

Urban areaS are developing rapidly on the stream reaches located below
the photos nurnbered IS, n,and47 (Mosaic5heet lT1(lex). Arnajerrporti<>n
of the waterShed above those photos is presently used for grazing livestock.
Out of a total watershed arCa of 34,000 acres, nearly 28,000 acres or 82
percent of the existing land uSe is in open space and grazing lsnds. By
1990, thc projected land use i~ expected to be 78 percent residential ,.;it)}
Ec percent of tho tot~l ~=c~ in fi~o.ae=e t:~ct:. The ~ecd f~r ~ ~~ste=

drainage plan and flood zoning regulations is eminent.

1,\TERPRfTAT!OMS A~'V RECOM,',!U,'VATrOI,S

TIle f.{,,,d for :tdequ.3.te channels to carr>' the f1o~'s of Sa"d Cro"~ ~nu
runoff fro... contributing aress has been recognized by city and c ountyplanners.
Suhdividers and developers al'e requirl.'d to submit proposed dr ainagep:ans
to the planning commissions for approval. lnthepast,drainagcplanshave

Re~ults of rnese ~"alyse5 ~h()~' a very _~,.,all ~mO\lN of exi~ting dev~lopments
located in the lOO-year flood hazard area. Two residences irur.edia~ely north of
Galley Road and west of the Ssnd Creek channel (Photo ~.o. 19) are in the