FLOOD02838

• County: Douglas
• County: Arapahoe
• Community: Greenwood Village, Aurora
• Stream Name: Cherry Creek
• Basin: South Platte
• Title: Probable Maximum Precipitation Study for Cherry Creek Reservoir - Final Report
• Date: 8/1/2003
• Prepared For: CWCB
• Prepared By: CWCB
• Floodplain - Doc Type: Project

1.3 Project Administration

The study was supported under contract with the CWCB in cooperation with
Arapahoe County, Aurora, Douglas County and Greenwood Village.

1.4 Cherry Creek Basin Topography and Location

The Palmer Divide is a unique topographic feature, located south of Denver and
extends eastward from the foothills of the Rocky Mountains into the plains of
northeastern Colorado. The Cherry Creek drainage basin is on the northern side of the
Palmer Divide between the Kiowa Creek and Plum Creek drainage basins. It is
approximately 10 miles wide in the east-west direction and approximately 40 miles long
in the north-south direction, Water in the basin flows south to north from the Palmer
Divide at the southern basin boundary to the Cherry Creek Reservoir at the northern end
of the basin, The total area of the Cherry Creek drainage basin is 410 square miles and
the drainage area upstream of Cherry Creek dam is 386 square miles.

For winter snowstorm events, the Palmer Divide provides significant upslope for
post-frontal snowfall on its north facing slopes. Upslope winds associated with these
winter snow storms produce enhanced winter precipitation within the Cherry Creek and
adjacent basins.

Warm saturated air from the Gulf of Mexico provides moisture for extreme warm
season rainfall events over eastern Colorado. A long fetch of upslope topography extends
from southern Texas into eastern Colorado. From there, the southern slopes of the
Palmer Divide along with barriers on the northern slopes of the Palmer Divide provide
additional orographic stimulus for rainfall production. For Gulf moisture trajectories that
track over central Texas into Kansas and then eastward into Colorado, the Palmer Divide
provides upslope terrain into the Bijou Creek and Kiowa Creek drainage basins.
Downwind of the highest terrain associated with these upslope regions, orographic
enhancement is lost. Additionally, the highest terrain acts as barriers for atmospheric
moisture below the terrain elevation. The location of the most relevant high terrain for
the Cherry Creek drainage basin varies with wind direction, The major terrain barrier for
southerly wind directions is the portion of the Palmer Divide that defines the southern
boundary of the watershed. For southeasterly to easterly wind directions, the east and
west boundaries of the Bijou Creek and Kiowa Creek basins provide the most significant
barriers. These physical features of the Palmer Divide topography limit moisture
availability from the Gulf of Mexico for storms over the Cherry Creek basin and are
significant when evaluating extreme storm characteristics for the Cherry Creek basin,
Figure 1.1 shows Cherry Creek dam, the general location of the basin is presented in
Figure 1.2, and Figures 1.3 and 1.4 show the basin location looking towards the north and
south.

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