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<br />9,2. Previous Studies
<br />
<br />Four previous studies have been performed on Dirty Woman and Crystal Creeks, The earliest
<br />of the studies is the Casey's 85-87 Subdivision 100-Year Historic Floodplain conducted by Tri
<br />Consultants (Ref, 9,1), In 1986, a study was completed by the Colorado Water Conservation Soard
<br />(CWCS) entitled, Flood Hazard Identification Report - Crystal Creek and Dirty Woman Creek (Ref. 9.2)
<br />FEMA completed studies on these basins in 1990 (FEMA) (Ref, 6,1) and more recently EI Paso
<br />County has conducted a Drainage Sasin Planning Study (DSPS) (Ref. 9,3),
<br />
<br />The most recent study by Kiowa Engineering used the HEC-1 model and divided the
<br />watersheds into 91 subbasins and conducted detailed routing of subbasin flows, This study was
<br />completed for existing and full development conditions, This study used a 2-hour storm of 2.88 inches,
<br />
<br />The FEMA study utilized the TR-20 model and divided the basins into 11 subbasins, This
<br />study utilized a 24-hour rainfall of 4.4 inches,
<br />
<br />The CWCS study used the Colorado Urban Hydrograph Procedure (CUHP) with a 1-hour event
<br />of 1,90-, 2.65-, and 3,02-inch rainfall depth for generating the 10-, 50-, and 100-year storms,
<br />respectively, SCS soil type within the watershed was assumed 50 percent "S" and 50 percent "C" with
<br />development resulting in 15 percent of the basin area impervious,
<br />
<br />The TriConsultants study utilized TR-20 modeling with a single basin defined for the Crystal
<br />Creek watershed, This study used a design storm of 4.4-inch rainfall depth over a 24-hour duration
<br />with a Type IIA distribution, Type "S" soils were assumed in their determination of CN, Table 9,1
<br />shows comparison discharges for Crystal Creek at the D&RG Railroad west of 1-25.
<br />
<br />Table 9,1, Summary of Crystal Creek Hydrology From Previous
<br />Studies,
<br />
<br />Report
<br />
<br />-. ."", .,....'.',.,
<br />Drainage Area ."..
<br />,,"..' "',
<br />
<br />0,75
<br />
<br />0,75
<br />
<br />078
<br />
<br />0,74
<br />0,74
<br />
<br />F'e~kp~!lh~
<br />.',' .....
<br />, 1JJJJWi'lar
<br />
<br />640
<br />
<br />660
<br />
<br />710
<br />
<br />644
<br />644
<br />
<br />,.
<br />
<br />CASEY
<br />
<br />CWCS
<br />
<br />FEMA
<br />
<br />DSPS (existing)
<br />(fully developed)
<br />
<br />9,3 Resource Consultants & Engineers, Inc,
<br />
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