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<br />Chatfield, Cherry Creek, and Bear Creek Reservoirs. The Denver gage <br />is located 5 miles upstream of Commerce City, and the length of <br />gaging records was from 1895 to 1973, excluding 1902, 1907, and <br />1908. The Henderson gage is located 9.5 miles downstream of <br />Commerce City, and the length of gaging station records used for the <br />analysis was from 1926 to 1973. <br /> <br />The peak discharge-frequency relati9nships for the reanalysis of the <br />2.03-mile reach of the South Platte River, from approximately 760 <br />feet downstream of westbound .Inters-tate Highway 270 to the upstream <br />corporate 1'imits of Commerce City at Franklin Street, were obtained <br />from a 1983 hydrologic study prepared by Merrick and Company under <br />contract to the UDFCD (Reference 11). The Merrick hydrologic study <br />was also used as the basis for the discharge-frequency relationships <br />in the UDFCD's 1985 flood hazard ar~a delineation study on the South <br />Platte River (Sand Creek to Oxford Avenue), prepared by Wright Water <br />Engineers, Inc. (Referen~e 12). <br /> <br />Peak discharges for the 10-, 50-, 100-, and 500-year floods for the <br />South Platte River and Sand Creek: in the study area are shown on <br />Table 1. <br /> <br />TABLE 1. SUMMARY OF DISCHARGES <br /> <br /> Drainage <br /> Area Peak Discharges <br />Flooding Source (square (cfs) <br /> and Location miles) 10-Year 50-Year 100-Year 500-Year <br />South Platte River <br /> At Franklin Street 3,8201 8,700 17,500 22,000 22,100 <br /> Upstream of <br /> Confluence with <br /> Sand Creek 3,8301 8,600 17,300 21,800 30,000 <br /> At Interstate 76 4,0251 17,500 29,000 37,200 60,000 <br />Sand Creek <br /> Quebec Street lB9 10,500 23,300 30,000 33,000 <br />Mouth at South <br /> Platte River 196 11 ,000 24,200 30,500 36,200 <br />1 Includes Area Above Chatfield, Bear Creek, and Cherry Creek Dams <br /> 3.2 Hydraulic Analyses <br /> <br /> <br />Analyses <br />community <br />floods of <br /> <br />of the hydraulic chara~teristics of streams in the <br />were carried out to provide estimates of the elevations of <br />the selected recurrence intervals along each stream <br /> <br />12 <br /> <br />