WSP02645

• File Number: 5700
• Description: Flood Protection Section - Flood Control Projects
• State: CO
• Basin: Statewide
• Date: 7/1/1985
• Author: BRW Inc - WRC Engine
• Title: Feasibility Study for the Cherry Creek Basin Drainageway - for Cherry Creek Basin TAC and Parker-Jordan Metropolitan District
• Water Supply Pro - Doc Type: Report/Study

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5. Floods

Historically. the principal cause of flooding within the drainage basin of
the Cherry Creek has been intense thunderstorms during the late spring and
summer months. Runoff from melting snow does not contribute to major flooding
because the altitude of the catchment is low. During the period from May to
August, warm moist air from the Gulf of Mexico combines with cool dry air along
the eastern plains causing a deflection upward where the unstable air is cooled
and precipitates over the front range. These storms are characterized by high
rainfall intensities of short duration which produce high peak flows and
moderate volumes of water. The largest floods occur when severe thunderstorms
pass over areas previously saturated by rain.

The history of flooding along Cherry Creek dates back to Indian accounts
of debris left by the retreating waters in the top of cottonwoods on the banks
of the harmless looking gulles. The earl iest recorded flood occurred in May
1864. five years after Denver was settled. Other major floods have occurred in
May 1876, May 1878, July 1885. July 1912, July 1922, August 1933, July 1946,
June 1965 and May 1973.

The annual peak flood record for Cherry Creek at Melvin is shown in
F i gure-4. The June, 1965 flood is the 1 a rgest flood to have occurred in the
Cherry Creek basin this century. On the 16th of June, 1965, a major storm
centered over the Plum Creek and Cherry Creek basins produced rainfall up to 10
inches in a 3 hour period. The recorded flows along the upper Cherry Creek
basin included 1,000 cubic feet per second upstream of Franktown, 39,000 cubic
feet per second near Melvin and 58,000 cubic feet per second at Cherry Creek
Dam. The heavy runoff caused major flooding along the main stem of Cherry
Creek from the vicinity of Franktown to Cherry Creek Reservoir. About 2,720
acres was reportedly flooded, Most of the bridges across Cherry Creek were
damaged or destroyed. Flood damages totaled $1,306,000 (Reference-2).

The flood frequency curves for annual peak discharges and for the partial
duration series for Cherry Creek at Arapahoe Road are shown in Figure-4. The
expected value of the lOa-year flood is 49,490 cubic feet per second according

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