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consideration channel stor,ilge along the study ["each. As a n~s.uLt, some peak discharge values for portions of the river show an increasing velocity with a decreasing drainage area. Peak discharges for the 10- and lOa-year floods on Sheep Draw were computed using the SCS Technical Release No. 20 computer program (Reference 6). Bas in characteristics needed for the program were taken from the USGS topographic maps, at a scale of 1:24,000, with a contour interval of 10 feet (Reference 7). Precipitation distributions were developed from information provided in the National Oceanic and Atmospheric Administration Atlas (Reference 8). The 50- and 500-year discharges were obtained by straight line interpolation and extrapolation of the 10- and 100- year values plotted on log-probability paper. Di scharge hydrographs for the 10- and lOa-year fl oods on Ashcroft and Eaton Draws were developed using methods suggested in Chapter 16 of the National Engineering Handbook, published by the SCS (Reference 9). Drainage areas and stream lengths necessary to construct the hydrographs were taken from USGS topographic maps at a scale of 1:24,000, with a contour interval of 10 feet (References 10 and 11). Precipitation distributions were developed from information provided in the National Oceanic and Atmospheric Administration Atlas (Reference 8). The hydrographs for Ashcroft Draw were routed through Arrowhead Reservoir us ing the Storage- Indication Method outline in Chapter 17 of the National Enaineerina Handbook (ReEerence 9). The 50- and 500-year discharges were obtained by straight line interpolation and extrapolation of the 10- and lOa-year values plotted on log-probability paper. Discharges for the Tri-Area Drainageway were computed using the SCS Technical Release No. 20 (Reference 6). Rainfall data used in the hydrologic analyses were obtained from the National Oceanic and Atmospheric Administration Atlas for Colorado (Reference 8), and soil and land use information were taken from maps prepared by the SCS (Reference 3). Discharge magnitudes for floods on the Big Thompson River were based upon an analysis of stream gaging data at the USGS stream gages located near Drake and La Salle. Because there are no streamflow gaging records between the La Salle gage and the upstream limit of study, discharge-probability relationships were developed for the intervening drainage area using uni t hydragraphs and flood routing techniques and rainfall probabilities from U.S. Weather Bureau Technical Publication No. 40. The peak discharges for the 10-, 50-, 100-, and 500-year floods for Coal Creek were developed by the SCS in a report entitled Flood Hazard Analvses. Coal Creek and Rock Creek. Boulder and Weld Counties. Colorado (Reference 12). The SCS used synthetic rainfall-runoff procedures, as described in the SCSls National En2ineerin2 Handbook (Reference 13), and the TR-20 computer program for flood routing (Reference 14) in order to establish the selected discharges along the stream. 10