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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swnmary of the basin parameters is presented in Table 11.2.
TABL!:; lLl -=- SUMMARY OF PC BASIN PARAMETERS
DRAINAGE AREA CURVE NUMBER TIME OF
SUBBASIN muare miles) CN CONCENTRATION. Ic
C1 1.01 69 1.40
C2 1.71 67 1.40
C3 1. 91 57 1.18
C4 0.36 61 0.48
Tl 1.64 56 1.04
T2 0.41 53 0.76
T3 0.25 53 0.86
T4 0.18 65 0.39
T5 0.34 80 0.50
T6 0.30 77 0.60
T7 0.45 54 0.69
T8 0.29 65 0.41
T9 0.20 73 0.19
TlO 0.93 69 0.84

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As-built plans for detention ponds 1 and 2 were obtained for
determIning the stage-volume-discharge data needed for TR-20
input. The rating curve provided in the MDRCH was used for
Pond 3. Detention at subbasin T3 was assumed neglIgible.

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The peak dIscharge values obtained In this study for the 24-
hour AMC II storm are presented in Table 11.3. The value of
1,280 cfs reported at P8 for the 100-year discharge is in close
agreement with the 1,252 cfs value obtained by the PCDB for the
24-hour storm. Both study values represent existing conditions
in the PC basin.

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In terms of the PCT basin, values obtained in this study are
significantly lower than those from the ESCC. Aside from the
fact that the prevIous study assumed fully developed
conditions, two other significant differences exist between
these studies. First of all, the ESCC generally assumed
hydrolol;ic soil types one step above those used in this study.
In other words; where a type "A" soil was assumed in this study
a type "B" soil was asstlmed in the other study and so on. The
second major difference Involves detention routing. It is
apparent from the ESCC discharge values that the storage
detention capability assumed in their analysis was not at as
high a <:apacity as presently exists.

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R€~OURC€ CON~UlTI\NT~ INC

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