FLOOD04285

• Designation Number: 270
• County: Adams
• Community: Westminster
• Stream Name: Big Dry Creek & Tributaries
• Basin: South Platte
• Title: Flood Hazard Area Delineation - Big Dry Creek & Tributaries
• Date: 11/1/1986
• Designation Date: 12/1/1987
• Floodplain - Doc Type: Floodplain Report/Masterplan

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TABLE 7 (cont'd.)
SUB-BASIN PARAMETERS FOR BIG DRY CREEK TRIBUTARIES ANALYSIS

Drainage Length Ia Loss Ra tes
Sub-Basin Area L Lca % Impervious Slope Pervious Impervious Initial Fina 1
Flooding Source Des igna ti on (Sq. Mi. ) (Mi) (Mi) Developed (Ft/Ft) Retention Retention in/hr in/hr Decay Rate
Walnut Creek 60 0.55 1.14 0.67 76.0 0.029 0.40 0.10 3.0 0.50 0.0018
62 0.22 1.14 0.62 55.0 0.018 0.40 0.10 3.1 0.51 0.0018
70 0.62 1.84 1.04 63.0 0.016 0.40 0.10 3.15 0.51 0.0018
72 0.16 0.63 0.34 12.0 0.025 0.40 0.10 3.0 0.50 0.0018
74 0.49 1. 70 0.98 42.0 0.020 0.40 0.10 3.0 0.50 0.0018
76 0.17 0.70 0.34 31.0 0.030 0.40 0.10 3.0 0.50 0.0018
78 0.15 0.91 0.61 48.0 0.026 0.40 0.10 3.6 0.54 0.0018
80 0.14 0.74 0.38 62.0 0.034 0.40 0.10 3.6 0.54 0.0018
82 0.10 0.78 0.53 51.0 0.014 0.40 0.10 3.3 0.52 0.0018
84 0.19 0.76 0.38 46.0 0.019 0.40 0.10 3.6 0.54 0.0018
86 0.28 0.76 0.37 67.0 0.028 0.40 0.10 3.8 0.56 0.0018
88 0.24 1.14 0.68 45.0 0.012 0.40 0.10 3.7 0.55 0.0018
122 0.12 0.57 0.19 37.0 0.033 0.40 0.10 3.8 0.55 0.0018
124 0.18 0.72 0.27 49.0 0.045 0.40 0.10 4.05 0.57 0.0018
125 0.14 0.51 0.27 31.0 0.013 0.40 0.10 3.8 0.55 0.0018
126 0.13 0.63 0.44 45.0 0.019 0.40 0.10 3.0 0.50 0.0018
Countryside 52 0.26 1.33 0.55 67.0 0.029 0.40 0.10 3.0 0.50 0.0018
Creek 56 0.31 0.85 0.32 40.0 0.030 0.40 0.10 3.0 0.50 0.0018
58 0.53 1.38 0.71 43.0 0.017 0.30 0.10 3.1 0.51 0.0018
North Branch 64 0.17 0.70 0.28 42.0 0.040 0.40 0.10 3.0 0.50 0.0018
Walnut Creek 66 0.69 1. 21 0.72 57.0 0.030 0.40 0.10 3.0 0.50 0.0018
68 0.51 0.98 0.42 26.0 0.030 0.40 0.10 3.15 0.51 0.0018
Ranch Creek 270 0.19 0.63 0.30 68.1 0.026 0.40 0.10 3.2 0.51 0.0018
272 0.50 1.00 0.53 56.9 0.023 0.40 0.10 3.0 0.50 0.0018
274 0.59 1.04 0.76 53.6 0.028 0.30 0.10 3.6 0.54 0.0018
Sou th Branch 262 0.12 0.42 0.16 44.0 0.037 0.40 0.10 3.0 0.50 0.0018
Ranch Creek 264 0.24 0.66 0.33 41.9 0.025 0.40 0.10 3.6 0.54 0.0018
266 0.13 0.83 0.59 42.1 0.023 0.40 0.10 3.0 0.50 0.0018
268 0.21 0.91 0.59 42.5 0.022 0.40 0.10 3.2 0.51 0.0018
Ketner Creek 10 0.18 0.83 0.34 35.0 0.019 0.30 0.10 3.0 0.50 0.0018
12 0.21 0.95 0.34 71.0 0.025 0.30 0.10 3.0 0.50 0.0018
14 0.22 0.95 0.43 46.0 0.015 0.40 0.10 3.1 0.51 0.0018

All parameters are for the 1985 version of the CUHPE program.
NOTE: The above parameters were calculated by Muller Engineering Company, Inc. as part of the hydrologic analysis for the Urban
Drainage and Flood Control District's Outfall Systems Study, Big Dry Creek (ADCO), Westminster and Vicinity.

UNIT HYDROGRAPH EQUATIONS (CUHPE Applica tion)
Cp =PCtAO.15 Qp = qpA
;, = Ct (LLca/So 0.5) 0.48
qp = 640 cp/ tp
Tp = 60tp + 0.5 tu

A description of the individual parameters can be found on page 7 of this report.

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