FLOOD05064

• Designation Number: 205
• County: Larimer
• Community: Fort Collins
• Basin: South Platte
• Title: Master Drainageway Planning - Cooper Slough, Boxelder Creek, Fort Collins, Larimer County, Colorado
• Date: 8/1/1981
• Designation Date: 1/1/1983
• Floodplain - Doc Type: Floodplain Report/Masterplan

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II. BASIN CHARACTERISTICS

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Basin Description

The Boxelder Creek drainage basin covers ,an area of 251 square miles in

Larimer and Weld Counties, Colorado, and Albany and Laramie Counties, Wyoming

(see Basin Map, Figure 1). Approximately 190.7 square miles of the drainage

basin is controlled area due to the SCS floodwater detention structures in the

basin. The watershed is about 32 miles long and about eight miles in width.

It flows in a southerly direction and is joined by Sand Creek, Rawhide Creek,

Coal Creek, Indian Creek, and Cooper Slough before it joins the Cache la

poudre River about three miles southeast of Fort Collins, Colorado. About 50

percent of the basin is grassland, 25 percent cropland, 20 percent brush and

forest land, ana 5 percent suburban development and other miscellaneous land

uses. The elevation of the watershed varies from 7720 feet above mean sea

level (msl) in the northern portion to about 4860 feet msl at the Cache la

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Poudre River confluence.

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Loottlol'l MIIp

The watershed lies within the Colorado Piedmont Section of the Great

Plains. The northern part of the watershed consists of rolling plateaus below

which is an area of hogback ridges and narrow mesas interspersed with narrow

valleys and canyons. To the east and south of these ridges and mesas, is an

area of rolling plains which extends south to the Cache la Poudre floodplain.

The Cooper Slough basin is north and east of Fort Collins, Colorado, of

which approximately 10.2 square miles is tributary area. The basin is about

six miles long and 1.75 miles wide. Cooper Slough flows in a southerly direc-

tion and joins Boxelder Creek in the vicinity of Prospect Street and 1-25 east

of Fort Collins, Colorado. The basin is undergoing development. The basin

elevation ranges from about 5100 feet msl at the north to 4910 feet mal at the

confluence with Boxelder Creek. The basin is generally flat with poorly

defined drainage patterns. The average annual precipitation is 14.0 inches at

Fort Collins, Colorado, with mean temperatures ranging from 690F in July to

260P in January. The mean annual temperature is 4BOF.

WYOMING

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Viotershed Boundary
---- Subwaterehed Boundory
---- Stote Boundory
--- County Boundary
Drainage Course
------ Irrigation Canal
Rood
B-30 Floodwater Retordlng Structure

KX)l Non-Iribulary Area

I / /1 Canlralled Area

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HiGh'olIlY I"

Vln. Dr.

SCALE

Ft. Collins

Study Area

The study area consists of the lower 6.4 miles of Boxelder Creek and

approximately two miles of Cooper Slough (Figure 2). The Soil Conservation

Service proposed in 1970 to construct five floodwater detention structures in

the Boxelder Creek basin. Since that time, four of the structures have been

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FIGURE I.

BASIN VICINITY MAP

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