FLOOD06459

• Designation Number: 96
• County: Douglas
• Community: Unincorporated Douglas County
• Stream Name: Happy Canyon Creek; Badger, Newlin, Baldwin, Sulph
• Basin: South Platte
• Title: Flood Hazard Area Delineation - Happy Canyon Creek, Badger Gulch, Baldwin Gulch, Sulphur Gulch & Tallman Gulch, Douglas-Araphahoe Counties, CO
• Date: 11/1/1977
• Designation Date: 1/1/1978
• Floodplain - Doc Type: Floodplain Report/Masterplan

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TABLE 3
FLOOD FREQUENCY, DISCHARGE

HYDRAULIC ANALYSIS

Analyses of the hydraulic characteristics of the streams were carried

out to determine the water surface elevations for floods of the

selected recurrence intervals for each stream. Cross section data

was obtained from 1" = 100' scale, 2 foot contour mapping.

Discharge Q, CFS
Stream and Location 10-yr. 50-yr. 100-y r . 500-y r.
Happy Canyon Creek
Confluence wi th Cherry Creek 2580 5230 6740 10730
Confluence wi th Badger Gulch 2340 4390 5520 8420
1-25 1970 3530 4390 6580
Badger Gulch
Confluence with Happy Canyon
Creek 560 1150 1490 2370
Newl in Gulch
Confluence with Cherry Creek 1970 3610 4810 8330
West Parker Road 1890 3450 4590 7920
Baldwin Gulch
Confluence with Cherry Creek 680 1270 1570 2390
Cross section #20 D/S from
SCS Flood Control Dam 40 120 240 820
SCS Flood Control Dam 700 1350 1670 2560
Antelope Trai 1 140 490 690 1250
Sulphur Gulch 6830
Confluence with Cherry Creek 2700 5440 10900
Confluence with Tallman Gulch 2690 5320 6660 10620
Upper Study Limit at Cross
Section #3 380 750 930 1450
Tallman Gulch
Confluence with Sulphur
Gulch 700 1390 1750 2820

Roughness Coefficients (Manning "n") were estimated by field in-

vestigation of the stream and its flood plain, use of Water Supply

Paper #1849, Open-Channel Hydraul ics by Ven Te Chau, Handbook of

Applied Hydraulics by Davis and Sorensen, and from SCS unpublished

studies. The roughness values for the main channels range from 0.03

to 0,06, and for the flood plain, range from 0.04 to 0.12. The

conditions affecting runoff and water surface elevation (CN, Tc, n, etc.)

are taken into account by the programs. Hydrologic soil cover

complexes and associated CN were obtained from SCS unpublished study

of the area and field investigations.

Water surface profiles for the 10, 50, and 100-year floods were

developed using Soil Conservation Service WSP2 and TR20 computer

programs.

The computed flood profiles for the 100-year storm are plotted on

the Flood Hazard Area Delineation drawings and tabulated at each

reference point in Tables 4 through 8. A complete record of the

technical calculations for the hydraulic analyses is available at

the Urban Drainage and Flood Control District,

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