FLOOD04641

• County: Denver
• Community: All
• Stream Name: All
• Basin: South Platte
• Title: Proposed Hydrology for use in Hydraulic Analysis of FEMA Flood Studies and Restudies
• Date: 9/1/1989
• Prepared For: State of Colorado
• Prepared By: Resource Consultants
• Floodplain - Doc Type: Educational/Technical/Reference Information

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under AMC II conditions. Both used 3.5 inches as the rainfall
depth for the 100-year storm. In addition, the rCDB analyzed a
24-hour rainfall of 4.4 Inch depth under the same criteria.

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The PCDB study was primarily concerned wIth development of PC
basin. Their detailed study was limited to analysis of
streamflow upstream of the PC culvert at Academy Boulevard
(point P8 on Figure 11.1). Flows cited in their report
downstr,eam of thIs point utilized the results of the older ESCC
without further analysis.

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Peak discharge resul ts from the three studies are presented in
Table 11.1. The location points refer to hydrologic discharge
poInts on Figure 11.1. "Historic" values representing existing
condItions were derived by the PCDB to represent the baseline
condition; these are the values presented in the table. The
ESCC only analyzed flows for future, fully developed conditions
in the basin; the values presented here from theIr study
reflect that condition.

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TABLE 11.1 " SUMMARY OF PC PEAK DISCHARGES FROM PREVIOUS REPORTS

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REPORT AND DRAINAGE AREA PEAK DISCHARGES ~
LOCATION i!,quare !!!1lill 10 YR 50 YR 100 YR 500 YR
Frs
Point PlO 9.70 2,300 5,500 7,600 15,400
ESCC
Point P7a 3.61 3,768
Point P8 5 . 00 ( 1) 2,560
Point PI0 10.18(1) 8,273
PCDB: 6-hr
Point P8 5.00 91.9
PCDB: 24-hr
Point P8 5.00 1,252

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In determining the hydrology for this study, the overall basIn
boundaries for both PC and PCT basins were kept nearly the same
as the PCDB and ESCC studies. Subbasin boundaries were
redefined as shown in Figure 11.1.

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(1) No area w',s presented for PC basin In the ESCC; these areas are
based on the assumption of 5.0 square miles for the PC basin as used
by the PC DB and RCI.

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11.3 l~drologic Analysis

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The PC basin was assumed primarily undeveloped; the derived
soil curve numbers closely matched those used by the PCDB.
Lower portions of PCT were assumed fully developed. The upper
basins were assumed only partially developed as reflects
existing conditions. In particular, subbasins 'fl, T2, T3 and
T7 still have a fair amount of open space. New Tc values were
determined to reflect the existing development conditions. A

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R€~OURC€ CON~UlTI\NT~ INC

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