FLOOD04800

• County: El Paso
• Community: Colorado Springs
• Stream Name: Cottonwood Creek
• Basin: Arkansas
• Title: Engineering Study of Cottonwood Creek Drainage Basin
• Date: 8/7/1979
• Prepared For: Colorado Springs
• Prepared By: Lincoln Devore
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Rainfall & Runoff Patterns

The NOAA weather station is located at

Peterson APB, approximately 12 miles southeast of the basin, so that

no official precipitation records exist for the basin. A number of

unofficial reports have been made over the years, however. precipi-'

tat ion in the lower (western portion) of the basin is approximately

the same as the annual average precipitation for Colorado Springs -

approximately 15 inches per year (38.1 em.). Precipitation in the

upper basin is a bit higher, averaging approximately 16 inches per

year (40.6 cm.). About 40% of the total precipitation is in the

form of snowfall, with greater amounts of snow measured in the Black

'1
Forest area. It must be emphasized that these figures are based on .,'
,,\"
fragmentary reports and should not be used for precise calculations. 1

The Black Forest area in the northerly '1')
L'l jl...i...Ct J
portion of the basin receives more snowfall than average for the geKeral

Colorado Springs area. This snow affects the base flow in Cottonwood

Creek, but has a relatively minor affect on the maximum, or flood

flow. As is the case over most of the metropolitan area, precipita-

tion in the basin is normally the greatest from May through August.

Major rainfall seems to come in two forms: 1) The slow, four day

'upslope' storm condition, which can produce high precipitation, but

over a longer period of time; and, 2) the intense thunderstorm of

high intensity but short duration.

Of these two types of storm normal to

the area, the high intensity, short duration thunderstorm prOduces

the greatest runoff flow, if such a storm is assumed to occur over

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