FLOOD00155

• County: Boulder
• Community: Boulder County
• Stream Name: Upper Boulder Creek, Fourmile Creek
• Title: Floodplain Information Report
• Date: 12/1/1981
• Prepared For: Boulder County
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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STUDY AREA DESCRIPTION

Vegetation in the basin below 11 ,000 feet is typically subalpine grasses
and brush with stands of conifer and aspen. Above 11 ,000 feet in the

Drainage Basin Characteristics
The Boulder Creek basin above the City of Boulder has a drainage area
of approximately 129 square miles. This typical front range canyon
(steep and narrow) contains both streams covered in this report: Boulder
Creek and Fourmil e Creek. Boul der Creek headwaters ori gi nate on the
eastern slope of the Continental Divide at elevations in excess of 13,000
feet. The steam flows generally eastward approximately 22 miles to the
City of Boulder and then out onto the the plains another 18 miles to its
confluence with St. Vrain Creek. Fourmile Creek, a tributary of Boulder
Creek, flows east then southeast through the mountains approximately 12
miles to its confluence with Boulder Creek at Orodell.

tundra area vegetation is generally sparse.
The Soil Conservation Service in their "Soil Survey of Boulder County
Area, Colorado" (Reference 8) classified the soils in the basin as part
of the Juget-Baller Association. This Association consists of rock
outcrops and sloping to very steep, shallow, very gravelly and stony
soils on mountains formed in residuum weathered from granites and
sandstones.

The land uses accompanying this Association generally relate to

wildlife habitat, recreation, and private home sites in a rural community

setti ng.

The approximate drainage areas at selected locations are shown in

Study Reach Description
Boulder Creek was studied in detail from Arapahoe Road upstream to

Table 1.

Barker Reservoir. Fourmile Creek was studied in detail from its mouth at

TABLE 1

Boulder Creek to a point just upstream of Sunset, Colorado. The lengths

of the streams studied were 14.2 miles on Boulder Creek and 10.9 miles on

Dra i nage Areas

Location

Area (sq. mi. )
38
102
129
7
25

Fourmile Creek. Stream bed elevations range from 5,447 feet mean

Boulder Creek at Barker Reservoir
Boulder Creek above Fourmile Creek
Boulder Creek at Arapahoe Road
Fourmile Creek at U/S StUdy Limit
Fourmile Creek at Mouth

sea-level (m.s.l.) to 8,022 feet m.s.l. on Boulder Creek in the study

reach. Both creeks can be classified as steep mountain streams. Stream

bed slopes range from 56 ft./mile to 581 ft./mile on Boulder Creek and
from 84 ft./mile to 343 ft./mile on Fourmile Creek.

The normal annual precipitation over the basins is approximately 23
inches (Reference 6). Average temperatures range from 750F in July to
250F in January (Reference 7). The topography of the Upper Boul der Creek
and Fourmile Creek basins is generally rugged, forested mountain slopes.

Development along both streams consists primarily of single-family

residences and their related structures. The development along Boulder

Creek is mainly in the lower half of the study reach while the structures

along Fourmile Creek are scattered throughout the study reach.

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