FLOOD02319 - Laserfiche WebLink

Home Browse Search

CDM · ~ u environmental engineers, scientists, planners, & management consul/ants . CAMP DRESSER & McKEE INC, March 17. 1981 Writer's Tower, Suite 1100 1660 South Albion Slreel Denver. Colorado 80222 o ~raijl~r"l 303758,4351 , ,,"MAR 19 1981 f:J P cY- sO ~~ Dr. John Liou C"., FEMA CONSERVA Ii",. "''-'" Denver Federal Center, Bldg. 710 Lakewood, CO 80225 Dear John: COM has completed the review of the Army Corp of Engineers hydrologic analyses for Kettle, Jimmy Camp and Cottonwood creeks in EI Paso County and Colorado Springs. The hydrologic analyses reviewed for Kettle and Cottonwood creeks included th COE 197~, Report on Hydrologic Investigations in Colorado Springs and EI Paso County, the 1976 COE Floodplain Information RepQrt fqr Cottonwood Creek and the 1979 Cottonwood Creek drainage study by Lincoln-Devore, Inc. The analyses reviewed for Jimmy Camp Creek are contained in the 1973 Flood Plain Information Repor~for Fountain and Jimmy Camp Creeks by the COE, the 1976 COE Report on Hydrologic Investigations, and the 1975 SCS Flood Hazard Analysis for Cottonwood Creek:J 5L. ~~ The 1976 COE hydrologic analysis for Kettle Creek used a unit 1(.Q.l.\ 'I V hydrograph proced ure and TM-1 to pred i ct peak flows for the 10-, C'~~~50-, 100- and 500-year storm events. COM has checked al I of the vC hydrologic parameters calculated by the COE and have found them i\- '->- to be accurate I y est i mated. COM recommends that the hydro I og i c y\ results in the 1976 COE work on Kettle Creek at Colorado Highway 83 be uti I Ized in the present Flood Insurance Study. An area reduction method wil I be used by COM to estimate the peak flow rates at other locations within the Kettle Creek basin. The suggested flow rates for Kettle Creek are presented in Table 1. l-q.l <#:"3'0 , '" (p'/ , ;t\' COM has rev I ewed the ex i st i ng hydro I og lei n format i on for Jimmy iLa Camp Creek and have found that a small discrepency occurs in the ,.,"'1' "0 peak lOO-year flow rates predicted between the 1973 and 1976 COE -,' . 1 studies. Similar methodologies were used (synthetic unit \4,'1"" ,(\1. hydrograph procedures), however the 1976 work uti I ized TM-l to -1'0 check the unit hydrograph results. We feel that the use of TM-l \~ is the cause of the difference in peak flow rates at the Fountain and Jiwmy Camp creeks confluence. The results of the 1973 COE FPIR and the 1975 SCS FHA for Jimmy Camp Creek compare favorably for al I frequencies, indicating the similarity of the procedures " used in each of these studies. Both the 1973 COE and the 1975 , .' _\C\1'J;;::;'2. SCS stud ies have been designated by the Colorado Water ')L '-, f'" .' Conservat I on Board and are current I y be i ng used by E I Paso County for floodplain regulation purposes. COM recommends that the hydrologic results as contained in the 1973 COE Flood Plain