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

I

I

Course. A sizable reservoir serves the irrigation needs of the
golf course and inadvertently provides detention storage at
point DW 1 on Figure 15.1.

I

In 1986, the Colorado Hater Conservation Board completed the
flood llazard ldentlJls:ation Report for Crystal Creek and Dirty
Woman i:reek (CWCB) (Reference 34). This is the only previous
study of the basin available for review.

I

15.2

Previous Studies

I

I

The CoIorado Urban Hydro graph Procedure (CUHP) was used for
analyzing this watershed In the CWCB. A I-hour event of 1. 90,
2.65, and 3.02-inch rainfall depth was used for generating the
10-, 50-, and 100-year storms, respectively. SCS soil type
within the watershed was assumed 50% "B" and 50% "C" with
development resulting In 15% of the basin-area impervious.

I

Peak discharges resulting from this study are presented in
Table 15.1.

I

TABU ld....l - SUMHA~Y QI DW PEAK DISCHARGES FROM PREVIOUS REPORTS

I

REPORT

DRAINAGE AREA
kquaJ:~ mllg!!l

PEAK DISCHARGES .!.!UlU.
AT MITCHELL AVENUE
lQ 1:13, 50 YR 100 )'R 500 YR

I

CWCB 5.0

1,230

2,620

3,360

5,800

15.3 Hydrolo,gic Analysis

I

I

The overall watershed basin boundary used in this analysis was
approximately the same as used for the previous study. The
basin was further divided into eight subbasins as shown in
Figure 15.1. It should be noted that subbasin 8 does not
contribute to the flow affecting the study reach, but was
included in order to compare results with the CWCB (it is
indicated by a dashed line on Figure 15.1). The assumed basin
parameters for Input to the TR-20 model are presented in Table
15.2.

I

I

TABLE 1~ -=- SUMMARY OF DW BASTN PARAMETERS

I

SUBBASIN

DRATNAGE AREA
~n.l1are miles)

CURVE NUMBER
CN

TIME OF
CONCENTRATION. Ic

I

1
2
3
I,
5
6
7
8

1.19
0.12
0.59
0.35
0.64
0.1,4
0.81,
0.81

67
67
67
67
68
67
68
67

0.74
0.42
0.78
0.72
0.85
0.60
0.84
1.15

I

I

61,

R€~OURC€ CON~UlTI\NT~ INC

I