FLOOD01135

• Designation Number: 223
• County: Boulder
• Community: Unincorporated Boulder County
• Stream Name: Upper Lefthand Creek
• Title: Floodplain Information Report - Upper Lefthand Creek, Volume II, Boulder County, Colorado
• Date: 8/1/1983
• Designation Date: 11/1/1983
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Much of the western portion of the drainage area is within Roosevelt
National Forest. The topography of the study area varies from rugged and
heavily forested mountains in the western part of the basin to slightly
rolling prairies at the mouth of the canyon. Average precipitation in
the study area is about 20 inches per year. Temperatures range from
highs over 900 F in the eastern portions of the study area to lows of
below -300 F in the upstream portions of the basin.
Soils found in the Upper Lefthand Creek and James Creek Basins are
of two primary types, namely, Fern Cliff-Allens Park-Rock outcrop complex
and Juget-Rock outcrop complex (Reference 5l. These soil complexes are
shallow with rapid runoff and high erosion potential. The soils are
suited for recreational purposes and wildlife habitat. Cover consists
of grass and trees. The soils are underlain by Precambrain granite and
gneiss. Some more recent intrusive rocks are also present.
The basin, historically, has supported the metal mining industry.
Present land use is primarily residential with some vacation homes and a
small permanent population.

(897 ft/milel near the upstream study limit. For this report, this reach
of Lefthand Creek is referred to as Upper Lefthand Creek.
James Creek was studied by detailed methods from its mouth to a
point just upstream of Jamestown, Colorado. Little James Creek, a left
bank tributary of James Creek was also studied by detailed methods from
its mouth to a point about 0.25 miles upstream. The total length of
James Creek studied was approximately 3.5 miles. Stream bed elevations
range from 6,330 feet m.s.l. to 6,990 feet m.s.l. on James Creek and from
6,955 feet m.s.l. to 7,049 feet m.s.l. on Little James Creek. Bed slopes
range from 0.015 ft/ft (79 ft/milel to 0.054 ft/ft (285 ft/milel on James
Creek. Bed slopes on Little James Creek range from 0.030 ft/ft
(158 ft/milel to 0.290 ft/ft (1,531 ft/milel. Little James Creek drains
approximately 2.9 square miles at its confluence with James Creek. James
Creek has a total drainage area of about 18.7 square miles at its con-
fluence with Lefthand Creek.
Development along Lefthand Creek and James Creek is limited to pri-
marily single family houses along the steep, narrow canyons. The com-
munities of Glendale, Rowena, and the Town of Ward are located along
Lefthand Creek in the study area and Springdale and Jamestown are located
along James Creek.
Obstructions to flood flows within the study reach include natural
obstructions such as large rocks, brush, and other vegetation growing
along the stream bank, and man-made obstructions such as bridges,
buildings, and culverts. During floods, these obstructions cause back-
water conditions that may increase the flood depths or they may cause
constrictions that increase the flow velocities. Brush washed out during
floods is carried downstream and may collect at bridges, in culverts, and

Study Reach Description
Lefthand Creek was studied by detailed methods from a point approxi-
mately 0.5 miles upstream of the Foothills Highway to a point near Ward,
Colorado, a stream length of about 17 miles. The contributing drainage
area varies from about 56 miles at the downstream study limit to 1.4
square miles at the upstream study limit. Stream bed elevations vary
from 5,615 feet mean sea level (m.s.l.l at the downstream study limit to
9,234 feet m.s.l. at the upstream study limit. Bed slopes range from
0.015 ft/ft (79 ft/milel near the donwstream study limit to 0.17 ft/ft

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