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Approach #1 The first approach to developing a 100 year flood discharge was to consider snowmelt runoff for the entire basin of 103.1 square miles at a mean elevation of 9,500 feet using the procedures described in Magnitude and Frequency of Floods in Colorado, Part 9 published by the u.s. Geological Survey. This is a regionalized analysis approach which has been developed by the u.s. Geologi- cal Survey based on stream flow gauge anal- yses for the vicinity. This procedure -2- Research by the Corps of Engineers and the u.S. Geologi- cal Survey indicates that critical flood events from this area of Colorado are typically snowmelt derived for elevations above 7,500 feet and rainfall derived for basins below 7,500 feet. Although the majority of the Sweetwater basin is situated above 7,500 feet, a small portion, 9.8 square miles, is located below elevation 7,500. This lower portion, in fact, produced the 1976 flood on Sweetwater Creek. Due to the elevation charac- teristics of the basin both snowmelt and rainfall derived flood events should be considered in developing the 100 year flood discharge. No gauge records exist on Sweetwater Creek. Gauges have existed for some years on Canyon Creek above New Castle and Elk Creek at New Castle. Although these gauges are located 25 miles from the Anderson Camp, the upper reaches of the drainage basins are within 8 miles of the upper limits of the Sweetwater Creek basin. The upper eleva- tion of all 3 basins are located on the Flat Tops Wilder- ness Area and the lower reaches.have similar canyon walls, vegetation cover, and elevation characteristics. It is therefore felt that the results of gauge records analyses on Canyon Creek and Elk Creek should represent good corollary data for Sweetwater Creek. Both Elk Creek and Canyon Creek discharge into the Colorado River at a lower elevation than Sweetwater Creek and therefore might be subject to more severe cloudburst type runoff events. Although 54 square miles of the Sweetwater basin are tributary to Sweetwater Lake, there should be very little, if any, reduction in the peak discharge from the upper basin during snowmelt events. This is due to the lake having an uncontrolled spillway and the fact that the lake is maintained at such a level as to have a constant overflow. For these reasons, no flood routing was at- tempted through Sweetwater Lake. The following paragraphs describe 3 different approaches taken to determining the design flood discharge for Sweet- water Creek.