WSP03196

• File Number: 8443.600
• Description: Narrows Unit - Studies
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 6/30/1975
• Author: Dames and Moore
• Title: Flood Study Narrows Dam South Platte River
• Water Supply Pro - Doc Type: Report/Study

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2903

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About 35 percent of, ,the area is at elevations greater than 7000
feet and 15 percent over 9000 feet. The drainage area is roughly
rectangular with the north-south dimension averaging about 160
miles and the east-west distance averaging about 85 miles. The
southern portion ,of the eastern boundary is a low divide between
the Kiowa Creek and Bijou Creek drainages. The Crow Creek drain-
age, which heads in Wyoming, forms the boundary in the north and
northeast. Most of the western boundary of the drainage area is
on the Continental Divide. The northwest boundary is the divide
with the North Platte River. The southwest and southern boundary
is the divide with the Arkansas River. Numerous tributary creeks
and rivers originate in the high mountain region; the primary
rivers are the Cache La Poudre and Big Thompson, and the primary
creeks are the St. Vrain, Clear, and Bear. The Corps of Engineers'
Cherry Creek Dam controls the Cherry Creek drainage south-southeast
of Denver. The Corps of Engineers' Chap field Dam on the South
Platte south of Denver controls the Plum Creek and the upper South
Platte River drainages. Two Forks damsite under consideration
for a location above Chatfield Dam is at the confluence of the
North Fork South Platte and the South Platte Rivers.

The total area above Narrows damsite (13,400 square miles) is sub-
divided as shown in Plate I-I. These subdivisions were specified
by the hydrological engineers for use in derivation of the design
flood. Areas obtained by'planimetry for use in this study are as
follows:

Subbasin
Designation

Subbasin Area
(square miles) ~/

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Chatfield Dam to
Two Forks damsite
Above Two Forks damsite

1,050
1,825
1,430
2,010
390
1,320
550
1,770

Above Narrows damsite to
, Chatfield Dam

440
2,615
13,400

10,345

~/ These areas were planimetered from the preliminary maps and were
used in this storm study. Slightly revised areas were used in
the flood study."

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