FLOOD02508

• Designation Number: 292
• County: Adams
• Community: Westminster
• Stream Name: Big Dry Creek
• Basin: South Platte
• Title: Flood Hazard Area Delineation - Bruchez Farms Property, Big Dry Creek at Wadsworth Parkway
• Date: 1/1/1988
• Designation Date: 3/1/1988
• Floodplain - Doc Type: Floodplain Report/Masterplan

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5

The 1973 study used the UD8.FCD guidelines in effect at that time. This rainfall event
had a totallOo-year depth of 3.15inches distributed over a 4-hour period with 2.25
Inches of rain occurring during the first hour.

While the two rainfall depths are approximately equal, the current duration of

rainfall is only half as long, resulting in a more intense rainfall event. This, In

turn, results In a greater volume of runoff and a higher peak discharge rate.

CUHP. The CUHP uses several parameters associated with the physical character-

Istics of the watershed to generate a hydrograph from each individua I subbasin

located within the total watershed.

These parameters include, for each subbasin, Its drainage area in square miles,
the length of Its main watercourse in mlles, the length to the center of the area In
miles, the slope of the main watercourse in feet per mile, the percentage of the
subbasin which is Impervious, Infiltration rates for the pervious portion of the
subbasin In inches per hour, and initial losses for both pervious and impervious
areas in inches.

The subbasins Included in the Big Dry Creek watershed upstream of the Walnut Creek

confluence with Big Dry Creek are shown in Figure 2. The drainage areas of each of

these subbasins In square miles and acres are listed in Table 1.