FLOOD06791

• County: Hinsdale
• Community: Lake City
• Stream Name: Henson Creek
• Basin: Gunnison
• Title: Henson Creek Flood Control Improvements
• Date: 12/1/1985
• Prepared For: Lake City
• Prepared By: Westwater Engineering
• Floodplain - Doc Type: Project

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Within the study reacnes, the Lake Fork has an average gradient of 0.6%
and an average channel widt~ Of EO feet. Normal water depths are 2.5 feet.
Henson CreeK, v;lth;n Its S:UGj reacn, "as an average gradient of 1.2%, average
width of 50 feet and average depth of 2 feet (during normal flows). Stream
sub-strate consists of large boulders, cobbles and bedrock. Streamside
vegetation consists of cottonwoods, willows and similar brush along both
streams.
Obstructions to floodflows within the study reach include both natural
obstructions such as vegetation growth, fallen trees, ice jams, etc. and
man-made obstructions such as bridges, buildings, fences and roadways. These
obstructions have a tendency to increase flood elevations upstream of the
obstructions and increase velocity downstream of the obstruction.
The stream valley above the Lake Fork study reach is essentially similar
to the study reach description (except it has a narrower flood plain). Lake
San Cristobal, a natural lake approximately 3.5 miles above Lake City, has a
dampening effect on potential floods such as those occurring from high intensity,
short duration rainfall. For long duration spring snowmelt and combination
rainfall, however, the effect of the lake on peak floodflows is minimal.
The stream valley above the Henson Creek study reach is very narrow and
steep. Trees and brush grow out over the channel in many areas along this
tight valley. High waters could carry great amounts of debris through the
study reach and accentuate the flood elevations.
The historical use of the floodplain has been for range, wildlife and
resort activities. Land adjacent to the streams is privately owned. These
areas have good plant cover and support meadow vegetation, willows and
cottonwood. Small areas within the floodplain are flooded annually and support
little or no vegetation. The growth of Lake City in recent years has forced
greater development in the flood plain. With this increased encroachment of
development in the flood plain, the flood hazard to the community is increased
and will continue in the future unless adequate measures are adopted to keep
the development outside the flood hazard areas.

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