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FLOOD00852
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Last modified
11/23/2009 1:21:24 PM
Creation date
10/4/2006 9:32:14 PM
Metadata
Fields
Template:
Floodplain Documents
County
Arapahoe
Community
Arapahoe County
Stream Name
Cherry Creek
Title
Cherry Creek River Run Improvements
Date
9/1/1986
Prepared For
Arapahoe
Prepared By
Greiner Engineering Sciences, Inc.
Floodplain - Doc Type
Floodplain Report/Masterplan
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<br />The structures were designed for a rural agricultural community with design <br />floods having a 25-year recurrence inte!:val. These rese,rvoirs generally only <br />affect the normal flow on Cherry Creek and only offer flood protection imme- <br />diately downstream of the dam locations with little or no effect on major <br />flood events along Cherry Creek. <br /> <br />HYDROLOGIC ANALYSES <br /> <br />The hydrological analysis for this reach of Cherry Creek was discussed in de- <br />tail in the 1984, Letter of Map Revision Report for Cherry Creek through River <br />Run development (Reference 1). Basically, the peak discharges were obtained <br />from the report "Flood Plain Informat:con, Cherry Creek, Cherry Creek Lake <br />through Franktown, Colorado, October, 1976" (Reference 4). The flows were <br />based on stream gage data and a statist [cal analysis of that data. The peak <br />flows on Cherry Creek, through the River Run ,site are listed below: <br /> <br />SUtlliARY OF DISCHARGES <br />CHERRY CREEK AT RIVER RUN <br /> <br />Location <br /> <br />Cubic Feet per Second <br />10 YR 50 YR lOa YR 500 YR <br /> <br />Upstream Property Line <br />Cross-Section l0530 <br /> <br />9,693 <br /> <br />29,119 <br /> <br />45,890 <br /> <br />142,460 <br /> <br />Downstream Property Line <br />Cross-Section 5620 <br /> <br />9,693 <br /> <br />29,119 <br /> <br />47,600 <br /> <br />l42,460 <br /> <br />HYDRAULICS <br /> <br />Although the primary area of interest [n this study is the reach of Cherry <br />Creek through the River Run site, the entire :reach of ChE!rry Creek from Cherry <br />Creek State Park to the Arapahoe-Douglas County line was used in the HEC-2 <br />analysis. <br /> <br />Flood elevations for the lOa-year recurrenCE! interval event were calculated <br />using the U.S. Army Corps of Engineers IlEC-2 step Backwater Computer Program <br />(Reference 9). The HEC-2 model used in the analysis is the 0.5 foot existing <br />conditions floodway run which was used in the June 1985 River Run LOMR and <br />previously approved by FEMA (Reference l). This model was modified to include <br />the grading on the River Run site. <br /> <br />The starting computed water surface ele\7ation at Cherry Creek State Park was <br />taken from the previous USACOE study in the basin (ReferE!1Ice 4). <br /> <br />Cross-sections used in the HEC-2 model were taken off topographic maps (Refer- <br />ences 5-7) or for sections 4,840 to ll,020 the sections were digitizE!d based <br />on recent Aerial Photogrammetry (Reference 8). The locations of the cros s <br />sections used in the model are shown on the floodplain map included in the <br />Appendix of this report. <br /> <br />- 3 -- <br />
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