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3.1 Hydrologic Analyses Hydrologic analyses were carried out to establish the peak discharge- frequency relationships for floods of the selected recurrence inter- vals for each stream studied in detail in the community. No streamflow gaging information is available for the major drainage- way flowing through Frederick. Gaging information on small watersheds in Colorado is currently being collected by the State Highway Depart- ment, but records to date are sporadic, and the period of record is short. The U.S. Soil Conservation Service method for developing synthetic hydrographs was, therefore, used to determine frequency discharges in this basin (Reference 6). This method is particularly suited to small agricultural watersheds. Rainfall data used in the hydrologic analyses were obtained from the National Oceanic and Atmospheric Administration Atlas for Colorado (Reference 7), and soil and land use information was taken from maps prepared by the u.s~ Soil Conservation Service (Reference 3). Frequency discharges for the SO-, 100-, and SaG-year floods in the Town of Frederick reflect overtopping of the levee at the south edge of town~ Discharges resulting from the levee failure were estimated using the California Breach Method and criteria used by the Colorado State Engineers' Office. Discharges were routed downstream through town using a U~S. Soil Conservation Service streamflow routing procedure (Reference 8)~ Failure of the levee increased the 100- year flood discharge by approximately 25 percent through Frederick. Peak dischargG-drainage area relationships for the Tri-Area Drainage- way are shown in Table 1. Table 1. Summary of Discharges Flooding Source and Location Drainage Area (Square Miles) Peak Discharges (Cubic Feet per Second) 10-Year 50-Year 100-Year 500-Year Tri-Area Drainageway at Frederick 3 440 1600 1810 2190 3.2 Hydraulic Analyses Analyses of the hydraulic characteristics of streams in the commu- nity were carried out to provide estimates of the elevations of floods of the selected recurrence intervals along each stream studied in the community~ 5