FLOOD11471 (2) - Laserfiche WebLink

Home Browse Search

The hydrologic analyses used for Sand Creek and Sand Creek's tribu- taries, as well as Jimmy Camp Creek and associated tributaries upstream of Peacedul Valley Road were obtained from S~S Flood Hazard Analysis reports (References 11 and 12). The SCS report used SCS hydrologic met~ods to develop peak discharges for the 10-, 50-, and 100-year recurrence intervals. The 500-year peak discharge was obtained by extrapolating the 10-, 50-, and lOO-year peak dis- charges on log-probability paper. Because of inadequate streamflow data on these streams, a synthetic rainfall-runoff evaluation pro- cedure was used to verify these studies. The SCS studies have been designated by the CWCB as complying with state statutory require- ments. For Jimmy Camp Creek below Peaceful Valley Road, the peak flow rates were developed by the COE and obtained from the December 1976 Report on Hydrologic Investigations (Reference 10). Synthetic unit hydrographs and rainfall data from the 11ational OCeanic a~d Atmospheric Administration report, Precipitation-Frequency Atlas of the Western United States (Reference 13), were used to develop the peak discharges. Flow rates for Fountain Creek, Upper Fountain Creek, and Monument Creek downstream of the U.S. Air Force Academy were adopted fron a COE 1976 hydrology report (Reference 10) and a 1973 Flood Plain Information report (Reference 6). This hydrologic method consists of gage station analysis, whereby stream gaging data have been analyzed to estimate peak flows for the various recurrence inter- vals. Peak discharges for Cottonwood Creek, Security Creek, Wide- field ~reek, and Windmill Gulch were also obtained from hydrologic information compiled in the 1976 COE report (Reference 10). In the urban basins and subbasins, synthetic unit hydrograp~s were used to develop the peakflow rates for the 10-, 50-, and 100-year re~urrence intervals. Rainfall patterns and amounts were obtained for the basins using the National Oceanic and Atmospheric Administra- tion (NOAA) data (Reference 13). The SOD-year peak discharge was obtained through extrapolation of t~e 10-, 50-, and 100-year flood results on log-probability paper. In the rural areas with natural- flow strea~s, the peak flow rates were obtained using hydrologic methods outlined in the Manual for Estimating Flood Characteristics of Na~~ra~-Flow Streams prepared jointly by the CWCB and the U.S. D~part~ent of t~e Interior Geological Survey (USGS) (Reference 14). P:ne Creek and ~or.ument Creek upstreaM of the U.S. Air Force Academy and Kettle Cree~ pea~ discharges were also determined using the C,CB and USGS hydrologic report (Reference 14). The usn curves ~sed in the synt~etic unit hydrograph ana:ysis were obtained using rainfall data from an SCS flood hazard analysis report for El Paso County (Reference 11), with soil survey information being obtained from another SCS report for El Paso County (Reference 4). 12