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TABLE 1 - SUMMARY OF DISCHARGES Flooding Source Drainage Area Peak Discharge (cubic feet per second) and Location (So. Miles) 10-Year 50-Year 100-Year 500-Year Dolores River Just downstream of the confluence with Lost Canyon Creek 567 6,800 11,500 14,500 36,000 Just upstream of the confluence with West Dolores River 270 3,700 6,000 7,500 20,000 West Dolores River At mouth 167 2,300 3,800 4,800 11,500 Mancos River At the Town 83 1,250 2,230 2,750 4,420 of Mancos Lost Canyon Creek At mouth 72 600 1,700 2,500 4,500 Chicken Creek At the Town 22.3 490 800 950 1,370 of Mancos 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. For flooding sources studied in detail, other than shallow flooding areas, water-surface elevations for floods of selected recurrence intervals were computed through the use of the COE's step-backwater computer program, HEC-2 (References 1 and 2). For the detailed study area encompassing the Dolores River, West Dolores River, and Lost Canyon Creek, basic cross section input was derived from surveyed cross section information furnished by the Colorado Water Conservation Board. For the detailed study area encompassing the Mancos River and Chicken Creek, basic cross section input was derived from topographic maps, with digitized cross sections utilized at the time of map compilation (Reference 2) . Locations of selected cross sections used 1n the hydraulic analyses are shown on the Flood Profiles (Exhibit 1). For stream segments for which a floodway was computed (Section 4.2), selected cross section locations are also shown on the Flood Insurance Rate Map (FIRM) (Exhibit 2). 7