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Having estimated the magnitude of flood peaks on the Gunnison River. a comparison of the flood hydroqraphs for the Colorado and Gunnison Rivers was made to determine when the peaks occurred. Figures 4, 5, and 6 show hydrographs during the high flow years of 1957, 1962, and 1984. It can be assumed that flood peaks on the Colorado and Gunnison Rivers occur at the same time since these hydrographs a.re nearly parallel. Thus, for study re.:lches downstream of the mouth of the Gunnison, the peak discharges on the Colorado are added to the flood peaks computed for the Gunnison. Thus. the proposed design discharges on the Colorado River study reach are as follows: 10.::Y.L__?0-Vr 100-vr 500-vr Study area above mouth 32,900 44,400 49.300 61,000 of Gunnison Study area below mouth 50,600 73,100 83,700 111.400 of Gunnison The previous FISs used the peak discharg'=s listed in the following table. Previous FISs 10-YL- 50-vr 100-vr 500-vr Study area above mouth 40,000 56,400 63.000 82,000 of Gunnison Study area below mouth 55,000 73,000 82,000 107,000 of Gunnison I : . B. Big Salt Wash and Little Salt Wash The Flood Hazard Information Report for Fruita, 1976 (3), discusses the hydrologic studies conducted by the Sacramento District of the Corps of Engineers on Big Salt Wash and Little Sal t Wash. Because streamflow gauging information was not available for these two streams. the Corps derived unit hydrographs by the S-graph method, based on an S-graph developed for Rifle Creek at Rifle. A standard project storm was developed for the washes from a compilation of precipitation records. Using frequency curves developed for other regional drainage basins similar in size to the study area drclinages, ratios of 100-year and 500-year floods to the standard project flood were determined. These peak discharges developed by the Corps will be used in the on-going studies also. The 1976 hydrologic studies also developed information on 10-'yea.r and 50-year flood events but the design discharges are not listed in the report. -8- 1.".:."