FLOOD08422

• Designation Number: 27
• County: El Paso
• Community: Colorado Springs
• Stream Name: Sand Creek
• Basin: Arkansas
• Title: Flood Hazard Analysis - Sand Creek, Colorado Springs, El Paso County
• Date: 7/1/1973
• Designation Date: 10/1/1973
• Floodplain - Doc Type: Floodplain Report/Masterplan

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PJtojee.ted CO'1tUUCi"..o

At the time this study was ~adc, it waS not possible to predict the
location Or dimensions of road crossings or channel modifications Which
~'ill occur in tne futUre. All of these changes wi 11 have a significant
effect on the potential flood line elevations and locations. For this
reason the study for projected conditions include only the effects of
additional runoff based On a change of land use expected by the year 1990.
The additional runoff waS routed through the stream channelS and flood
plains using existing topographic conditions. In comparing the results of
the study, existing conditions with projected conditions, the two analyses
sho~' very little difference in potential flood line elevation~. In ll1any
instances, the elevation change amounts to less than one foot. The signi-
ficance of this change in terms of hazard is dependent upon future flood
plain use and the location of future develop,'ents.

Exhibit B is a selection of typical valley cross-sections illustrating
the configuration of the stream channels and adjoining flood plain areas.
The SO-, 100-, and SOO-year flood lines arc sho"" "ith a notation of eleva-
tion differential bet~een existing and projected runoff conditions. Table I,
Flood Plain Reference Data, includes flood line elevations for the 100- and
SOO-year floods under c~isting and projected runoff conditions for each cross-
section in the study area.

INTfRPRffAT10NSAIfl)RECO),{J,lfNVATlONS

Ine need for adequate channelS to carry the flows of Sand Creek and
runoff froll1 contributing areaS has been rccol;nizedby cjty and CO untyplanners.
Subdividers and dcvelopers arc rcquired to subnitproposed dra inageplans
to the planning commissions for approval. In the past, drainage plans have

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been preparcd singularly or on a plat by plat basis. Locations of potential
flooding by various frequency storms en the najor channels of Sand Creek
were not kno~~ until this flood hazard analyses was completed. The analyses
can be used in developing a master drainage plan for the entire Sand Creek
';atershed.

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Primary purpose of this report is to provide maps of the flood ha.ard
areas so that local governll1ents can develop flood plain 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 Water Conservation Board. The lOa-year flood
line delineation should be useful when application is made for approval of
flood zone regulations.

FactoM Annec.tbtg F{codbtg

Urban areas are developing rapidly on the stream reaches located below
thc photos numbered 15, 22, and 47 (Nosaic sheet Index). A major portion
of the watershed above these photos is presently used for gra.ing livestock.
Out of a total watershed area of 34,000 acres, nearly 28,000 acres or 82
percent of th" existing land use is in open space andgradng lands. By
1990, the projocted land use is e~ected to be 78 percent residential with
56 percent of the total area in five_acre tracts. lno need for a ~aster
drainage plan and flood zoning regulations is eminent.

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Results of these analyses show a very small amount of existing developments
located in the lOO-yearfloodhazard aren. Two residences immediately north of
Calley Road and west of the Sand Creek channel (Photo No. 19) arc in the