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<br />frequencies were obtained from the COI! during the preparation <br />of the 1973 Special Flood Hazard Information Report. <br /> <br />The discharges developed in 1973 by the COE for East Toll Gate <br />Creek were used in this utudy. Due to the more recent <br />construction of Quincy Dam, the discharges developed by the <br />COE for Upper West Toll Gate Creek were reevaluated. The 500- <br />and 100-year flood hydrographs for West Toll Gate Creek, <br />obtained from the Omaha District office, were routed through <br />the Quincy Dam Spillway. By routing these hydrographs through <br />Quincy Dam the 100-year flood discharge is reduced from 4,840 <br />cfs to 2,300 cfs; the SOD-year discharge is reduced from 7,600 <br />cfs to 5,300 cfs. Because of a perimeter channel around the <br />reservoir with a capacity of approzimately 1,000 cfs, the 50- <br />year and 10-year flood discharges are not changed <br />significantly from those computed ffr the uncontrolled <br />condition. <br /> <br />Runoff predictions for the West Toll Cate Creek Tributary, the <br />Cherry Creek Spillway Drain and Unn~d Creek were made by the <br />COI! and are represented in the 1973 Special Flood Hazard <br />Information Report (Reference 13). The 50- and SOD-year <br />discharges were determined by eztrapolating the data computed <br />for the 10-, 25-, and 100-year flOOds. <br /> <br />The discharges for Westerly Creek were taken from the Phase A <br />Report of the Westerly Creek Master Plan completed in January <br />1976, by Camp, Dresser & McKee, Inc., for the Denver Region <br />Urban Drainage and Plood Control District (Reference 14). The <br />Colorado Urban Hydrograph Procedure, as outlined in the Urban <br />Storm Drainage Criteria Manual (Reference 17), was used to <br />determine the peak discharges for the 2-, 10-, and 100-year <br />storms. The 50- and SOD-year discharges were determined by <br />interpolating and eztrapolating the data computed for the 2-, <br />10-, and 100-year floods. <br /> <br />The discharges for Sable and Granby Ditches were determined <br />utilizing the Colorado Urban Hydrograph Procedure, as outlined <br />in the Urban Storm Drainage Criteria Manual (Reference 17). <br />Peak .discharges were determined for the 10- and 100-year <br />floods. The 50- and SOD-year discharges were estimated by <br />assuming a straight line log probability relationship between <br />the 10- and 100-year floods. <br /> <br />Prequency-discharge drainage-area data for the above-mentioned <br />streams are shown in Table 1. <br /> <br />DiSCharges used for the approzimate studies of Side Creek <br />Tributary, aDd Columbia Creek were taken from the drainage <br />area discharge relationship developed from the COI! information <br />on East Toll Gate Creek. <br /> <br />13 <br />