|
<br />Peak discharges for Bear Creek, Camp Creek, Cheyenne Creek, South Shooks Run,
<br />Cottonwood Creek, Security Creek, Widefield Creek, and Windmill Gulch were also
<br />obmined from hydrologic information compiled in the 1976 USACE report (Reference 16),
<br />In the urban basins and subbasins, synthetic unit hydrographs were used to develop the
<br />peakflow rates for the 10-, 50-, and IOO-year recurrence intervals, Rainfall patterns and
<br />amounts were obtained for the basins using the NOAA data (Reference 19), The 500-year
<br />peak discharge was obmined through extrapolation of the 10-, 50-, and lOO-year flood results
<br />on log-probability paper. In the rural areas with natural-flow streams, the peak flow rates
<br />were obmined using hydrologic methods outlined in the Manual for Estimatin!: Flood
<br />Characteristics of Natural-Flow Streams prepared jointly by the CWCB and the USGS
<br />(Reference 21),
<br />
<br />,
<br />
<br />Pine Creek, Pine Creek tribumries, Kettle Creek, North Monument Creek, Carpenter Creek,
<br />Butler Creek, and Monument Creek upstream of the U,S, Air Force Academy peak
<br />discharges were also determined using the CWCB and USGS hydrologic report (Reference
<br />21), The "S" curves used in the synthetic unit hydrograph analysis were obtained using
<br />rainfall data from an SCS flood hazard analysis report for EI Paso County (Reference 17),
<br />with soil survey information being obtained from another SCS report for EI Paso County
<br />(Reference 7),
<br />
<br />The hydrologic results for Douglas Creek (North and South), Mesa Basin, Rockrimmon Basin
<br />drainages, Spring Creek, and Templeton Gap Floodway were developed using an SCS report
<br />entitled Procedures for Determinin~ Peak Floods in Colorado (Reference 22), This
<br />methodology is consistent with those outlined in the City of Colorado Springs storm runoff
<br />criteria manual (Reference 23). and has been used widely to determine design capacities for
<br />flood-control projects throughout the city, For these basins, future development conditions
<br />were assumed to obtain the lOO-year frequency flow rate, Field checks were carried out to
<br />check changes in land use since completion of drainage studies, to verify channel alignments,
<br />and to check major hydraulic structures which could affect basin hydrology, The assumption
<br />of fully developed conditions in the basins was acceptable for use in the study, Since the
<br />drainage reports contained only lOO-year peak discharges, flow rates for the 10-,50-, and
<br />500-year recurrence intervals were estimated in accordance with the procedures outlined in
<br />the Colorado Springs storm runoff criteria manual and the SCS Procedures for Determinin!:
<br />Peak Flows in Colorado (References 23 and 22), The discharge-frequency relationship for
<br />Spring Creek was prepared using the SCS methods in conjunction with the Colorado Springs
<br />storm runoff criteria manual (Reference 23), Soil information was obtained from an SCS
<br />survey of EI Paso County (Reference 7),
<br />
<br />Peak flow rates were developed for the Peterson Field Drainage using the Peterson Field
<br />Master Drainage Report (Reference 24), and the Colorado Sprin!:s Municipal AiI:port
<br />Runway] 7L-35R Gradin!: and Drainal,'e Plan (Reference 25), Peak flows from the master
<br />drainage report were reevaluated by routing flows through the detention basins recommended
<br />in the Colorado Springs storm runoff criteria manual (Reference 23),
<br />
<br />Peak discharges for Dry Creek and its tributaries were obtained from the Dry Creek Master
<br />Draina!:e Study (Reference 4), Analyses of the peak flow rates for the 10- and 50-year
<br />recurrence intervals were not available,
<br />
<br />20
<br />
|