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intake pipe to a culvert located under the detention pond and Hampden Avenue (State Highway 30). Peak discharges for Sanderson Gulch and Weir Gulch were determined as part of the 1972 UDFCD Major Drainageway Planning report (Reference 41). The 10-, 50-, and 100-year discharges were calculated using the Colorado Urban Hydrograph Procedure (Reference 40) for fully developed basin conditions. The SOO-year discharge was extrapolated from the data. Peak discharges on Weir Gulch downstream of Barnum Lake were revised to reflect channel improvements at Barnum Lake and increased culvert capacity at West 6th Avenue (U.S. Highway 6). Peak discharges for First Avenue Tributary and Dakota Avenue Tributary were determined as part of the 1977 UDFCD Flood Hazard Area Delineation report (Reference 20). Those discharges were calculated in accordance with the Colorado Urban Hydrograph Procedure (Reference 40) assuming fully developed basin conditions. The subbasin hydrographs were routed downstream. The Puls Method was used to calculate discharges at locations where storage had a significant effect. Peak discharges for Sand Creek were determined as part of the 1977 UDFCD Flood Hazard Area Delineation report (Reference 42). The hydrologic analysis was based on the development of a surface- runoff model of the Sand Creek basin using the runoff block of the EPA Storm Water Management Model (Reference 37). Discharge hydrographs developed from the model were then routed along the main stem of Sand Creek by use of an unsteady flow-routing procedure developed by James A~ Harder and modified by the Missouri River Division of the COE. 'Discharge probability relationships were developed by inserting precipitation-frequency val~es (Reference 43). The discharges were calculated for fully developed basin conditions. Peak discharges for the South Platte River were determined as part of the September 1985 UDFCD Flood Hazard Area Delineation report (Reference 44). Peak-frequency values for the South Platte River were taken from the May 1983 Hydrologic Study report prepared by Merrick and Company under contract to the UDFCD (Reference 45). Peak discharge-drainage area relationships for all streams studied by detailed methods are shown in Table 2. 3.2 Hydraulic Analyses Analyses of the hydraulic characteristics of flooding from the sources studied were carried out to provide estimates of the eleva- tions of floods of the selected recurrence intervals. Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles (Exhibit 1). For stream segments where a floodway was computed (Section 4.2), selected cross section locations are also shown on the Flood Insurance Rate ~ap. 18