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logical Unit 14020005; period of record: 1895, October 1896 to September 1899, 1906, October 1916 to current year). October 1894 to December October 1901 to October The variation of the quantity of the peak flood within the study reaches was studied. From this analysis, it was concluded that the runoff yield during peak flows from the low lying areas is small. This result supports the conclusion that snowmelt from upper elevations is the major contributor to the peak flows. Peak discharge-drainage area relationships for Clear Creek and South Clear Creek are shown in Table 1. TABLE 1 - SUMMARY OF DISCHARGES FLOODING SOURCE DRAINAGE AREA PEAK DISCHARGE (cfs) AND LOCATION (SQ MILES) 10-YEAR 50-YEAR 100-YEAR 500-YEAR Tomichi Creek 1,061.0 1,501 1,904 2,050 2,340 . At Gunnison (Hydrologic Unit 14020003) At Parlin 427.0 716 874 924 1,017 Gunnison River Near Gunnison 1,012.0 5,762 7,967 8,930 11,256 (Hydrologic Unit 14020002) Near Somerset 531.0 5,600 8,000 9,200 11,300 (Hydrologic Unit 14020004) 3.2 Hydraulic Analyses Analyses of the hydraulic characteristics of flooding from the riverine sources studied were carried out to provide estimates of the elevations of floods of the selected recurrence intervals. Water-surface elevat ions for the 10-, 50-, 100-, and 500-year floods for the sources studied were computed using the COE HEC-2 step-backwater program (References 1 and 2). Cross sections for Gunnison River and Tomichi Creek were digitized from orthophoto contour maps flown in May 1978 (Reference 6) and May 1980 (Reference 7), coupled with appropriate field verification. North Fork Gunnison River basic input was from field survey data furnished by the Colorado Water Conservation Board (CWCB) and 8