FLOOD09606 - Laserfiche WebLink

Home Browse Search

National Oceanic and Atmospheric Administration report, precipi- tation-Frequency Atlas of the Western United States, Volume III, Colorado (Reference 13). The runoff models were calibrated against the discharge records available at the respective stream gages. The flood discharge values used for Tucker Gulch, Cressmans Gulch, Cressmans Gulch Old Channel, East Fork Kenneys Run, West Fork Kenneys Run, West Fork Kenneys Run Tributary No.1, North Fork of West Fork Kenneys Run Tributary No.1, West Fork Kenneys Run Tribu- tary No.2, and Deadman Gulch were obtained using the Colorado Urban Hydrograph Procedure (CUHP). A detailed description of the CUHP is given in Volume I of Urban Storm Drainaqe Criteria Manual (Reference 14). The 10-, 50-, and 100-year flood discharges were calculated by the CUHP program. The design rainfall data were supplied by the UDFCD based on values obtained from Precipitation- Frequency Atlas of the Western United States, Volume III, Colorado (Reference 13). Peak discharges at selected locations in the study reaches were obtained by routing the flood hydrographs for each subbasin computed by the CUHP. The flood discharge values used for Lena, Jackson, and Apex Gulches were obtained from a 1975 study done for the UDFCD by Wright-McLaughlin Engineers (Reference 15). In this study, the CUHP was used to calculate the 10-, 25-, and 100-year discharges for present and future development conditions. The design rainfall used in the study was supplied by the UDFCD based on information from Precipita- tion-Frequency Atlas of the Western United States, Volume III, Colorado (Reference 13). During this study, the drainage area of Lena Gulch was field checked to determine that 1982 development conditions would be properly reflected by the estimated future development conditions reported in the 1975 UDFCD study. The future development conditions for flood discharge values from the 1975 UDFCD study were determined to be valid for this Flood Insurance Study. The 50- and 500-year discharges were estimated from the frequency curves based on the 10-, 25-, and 100-year discharge values. Peak discharge-drainage area relationships for streams studied by detailed methods, except Cressmans Gulch Old Channel, are shown in Table 1. The 100-year flood discharges used for the approximate study reaches were determined from a discharge-drainage area curve that was developed from discharges computed by the CUHP for several basins in the immediate vicinity of Golden. 3.2 Hydraulic Analyses Analyses of the hydraulic characteristics of the flooding sources studied in the community were carried out to provide estimates 12