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<br />unpublished SCS study of the area, and land use and natural plant <br />cover maps of Douglas County, Colorado (References 8 and 9, <br />respectively). "alues of 10-, ~O-, 100-, ~n~ ~OO-yp~r ppRk ~i~- <br />charges were obtained using the SCS TR-20 computer program (Refer- <br />ence 10). The computed peak discharges compare favorably with the <br />peak discharges estimated using USGS Technical Manual No. 1 <br />(Reference 11). <br /> <br />Discharge magnitudes for Cherry Creek floods were based on an <br />analysis of stream-gaging data at the USGS stream gages located <br />approximately 2.5 miles south of Franktown and 6 miles northwest <br />of Parker. This information was obtained from a COE Flood Plain <br />Information report (Reference 12). Discharge-frequency relation- <br />ships for the upstream and downstream limits of the study reach <br />were developed using data from the Franktown and Parker stream <br />gages, respectively. The 32 flood-retarding structures in the <br />Cherry Creek basin constructed by the SCS were taken into <br />consideration. <br /> <br />using two UDFCD reports (References 13 and 14), a discharge- <br />drainage area curve was developed for streams studied by <br />approximate methods. This method was used for Jordan Road <br />Tributary and Oak Gulch. <br /> <br />Peak discharge-drainage area relationships for the streams studied <br />in detail, Cherry Creek, Sulphur Gulch, and Tallman Gulch, are <br />shown in Table 1. <br /> <br />3.2 Hydraulic Analyses <br /> <br />Analyses of the hydraulic characteristics of flooding from the <br />sources studied were carried out to provide estimates of the <br />elevations of floods of the selected recurrence intervals. <br /> <br />For Sulphur and Tallman Gulches, the water-surface profiles for <br />theJ,.o:::,50:::, 100:::'dan_d!j.oO:::year flood" were developed using the <br />SCS WSP-2 computer program (Reference 15)~. These profiles arid <br />elevations were compared with historic floods and the flood stages <br />then determined. <br /> <br />Water-surface profiles for floods along Cherry Creek were obtained <br />from the 1976 COE Flood Plain Information report (Reference 12). <br /> <br />The water-surface profiles for 10-, 50-, 100-, and 500-year floods <br />on Cherry Creek were developed using the COE HEC-2 step-backwater <br />computer program (Reference 16). The computations were based on <br />channel and flood plain conditions as represented by survey data <br />gathered in April 1975 and as supplemented by later field investi- <br />gations. <br /> <br />8 <br />