FLOOD09948

• County: Hinsdale
• Community: Lake City
• Stream Name: Gunnison River, Henson Creek
• Basin: Gunnison
• Title: Floodplain Information Report
• Date: 10/1/1985
• Prepared For: Lake City, Hinsdale County
• Prepared By: Westwater Engineering
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

Purpose and Scope
The purpose or this report is to pro~ide the Town of La~e Ci~y and HinsCaie
County officials with a tocl for planning purposes and to regulate the land use
of areas within the flOOdplain of the Lake Fork of the Gunnison River and ~en$on
Creek in order to minimize flood damages and dangers to both the property and
human life. The report contains information on historical floods in the Study
reach, existing basin and channel parameters influencing the flood hazard, and
information related to the 10-, 50~, 100~ and 500~year frequency floods.

Mapping and Surve.1S
Topo~raphic "'.a~ping for this st'Jdy was prOVIded by the ColoradO '~ater
C~nservdtion Board. The 1ap~lng was prepared in 1975 by Merrick and Co~pa~y
of Den'/er, Colorado. The!1'appingfurnishedisatascaleof 1":2CO' and
~n" contour int"rval is 5 "eet. The datum is mean sea level.

The report presents flooded area maps delineating the extent of the lOC~
and 500-year floods, a one~foot rise floodway, water surface profiles, and
typical floodplain cross sections shewing the water surface elevations for the
10~, 50-, 100., and 500~year floods. Supplemental information depicting the
backup data and calculations for the hydrologic and hydraulic analysis are
presented in the TecMical Addendum. This information is useful for planning,
designing and implementing land use activities within the study area.

Sixteen cross-sections of the Lake Fork of the Gunnison River an dfolJr
cross-sections of Henson Creek were surveyed by the ColoradO Water Conservation
Board in August, 1982. These cross~sections, in addition to others required
for hydraulic accuracy, are shown on the mapping and are designated by integer
numbers. The cross~sections defining the 8~ Street Bridge were revised from
construction plans to show the hydraulic effects of the proposed new bridge,
expected to be constructed by the end of 1986.

Colorado Water Conservation Board/Mr. Larry Lang
U.S. Geological Survey
Town of Lake Clty!~r. Scott Ross and Sheriff Burton smith
Lake City SilverWorld!Mr. Grant Huston
Mr. Ken Charles, Region IX Planning Commissioner

The 5 foot contour base maps have the following alIowabletolera nce: 10-:;
of contours may ha~e tolerances of t5 feet and 90% may have tolerances of
t2.5feet. The field surveys have an allowable tolerance of 0.5 feet.
Whenever differences exist between base map elevations and field sur~eys. the
field s.uneys shall govern. The Flood Profiles (Plates 9 through 15) are based
on field surveys. For further clarification of actual field elevations refer
to the Flooded Area Maps for locations and elevations of two USGS Benchmarks
Jnd several field-s~rveyed ground elevations. USGS Benc~~~rk 8681, elevation
8675.36, is located at the northeast corner of tne La~e CIty Hank BUilding.
USGS Benchmark 8663, elevation 8657.6, is located on the southwest corner of
the Elementary School playground.

Acknowledgements
We wish to aCknowledge the assistance and cooperation of the agencies,
firms,orgarJizations and individualS whi.char<olistedbejow. M,;,nyTow'll
and county officials and private citizens provided much information that was
essentialtotheunderstandingofthefloodingproblemsinthestudyarea.
The efforts of all these who contributed ~o this st~dy are apprecia~ed.

Maps delineating the 100. and 500-year floods are available for re~iew
at Lake City Town Hall and the Hinsdale County Court House.

Related FloOd Studies
No co~parable flood plaIn studies of record have been prepared on
the LaKe Fork of th" Gunn:son River or Henson Creek in the reach covered by

this ~e~ort.

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