<br />CDM ·
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<br />CAMP DRESSER & McKEE INC,
<br />
<br />environmentsl engineers, scientists,
<br />planners. & management consultants
<br />
<br />Writer's Tower, Suite 1100
<br />1660 South Albion Sfreet Denver, Colorado 80222
<br />303758-4351
<br />
<br />October 16, 1981
<br />
<br />Dr. John Liou, FEMA
<br />Building 710
<br />Denver Federal Center
<br />Lakewood, CO 80225
<br />
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<br />
<br />Dear John:
<br />
<br />Camp Dresser & McKee Inc. (COM) has comp1 eted the hydrologic anal yses for
<br />the Douglas Creek, Mesa Basin, Peterson Field, Rockrimmon Basin, Templeton
<br />Gap, Spring Creek, and Sand Creek basins, for the Colorado Springs Flood
<br />I nsurance Study.
<br />
<br />To predict the peak 10-, 50-, 100-, and 500-year flow rates for Douglas
<br />Creek, Mesa Basin, Rockrimmon Basin, Templeton Gap, and Spring Creek, the
<br />Soil Conservation Service, "Procedure for Determining Peak Flows in
<br />Colorado," was util i zed. The development in each of the basins is
<br />continuing at a constant rate and will be near full development at the time
<br />of canp 1 eti on of the Flood I nsurance Study. It was therefore determi ned to
<br />use future development conditions in the hydrologic analysis, as stated in
<br />COM's letter of August 10, 1981.
<br />
<br />For all basins a thorough search for existing up-to-date information was
<br />performed by CDM. Current drainage basin studies were obtained fr~ the
<br />City of Colorado Springs, a Flood Hazard Analysis was obtained from the
<br />Soils Conservation Service (SCS), and a hydrologic analysis was obtained
<br />which was prepared by the Corps of Engineers for Flood Insurance Studies in
<br />E1 Paso County and Colorado Springs, Colorado. All reports were then field
<br />checked by CDM to determine if conditions in each basin had changed to
<br />warrant a new hydrologic analysis.
<br />
<br />Below is a summary of the analysis for each flooding source. A detailed
<br />summary of all flooding sources will be submitted with the review copy of
<br />the Flood Insurance Study for Colorado Springs.
<br />
<br />Dougl as Creek
<br />
<br />All basin characteristics were obtained from the March, 1981,
<br />"Douglas Creek Drainage Basin Study," by Leigh Whitehead Inc.
<br />Only the 100-year discharge was calculated in this report. COM
<br />calculated the 10- and 50-year frequencies using a 6-hour rainfall
<br />obtained from the City of Colorado Springs 1979 "Determination of
<br />Storm Runoff Criteria." The SOD-year rainfall was determined by
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