FLOOD04613

• Designation Number: 133
• County: Chaffee
• Community: Buena Vista
• Stream Name: Cottonwood Creek
• Basin: Arkansas
• Title: Flood Hazard Analysis - Cottonwood Creek in the Vicinity of Buena Vista, Chaffee County, CO
• Date: 7/1/1978
• Designation Date: 3/1/1979
• Floodplain - Doc Type: Floodplain Report/Masterplan

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INVESTIGATIONS, ANALYSES, ANO TECHNICAL OATA

Most of the data for the 127 crOss-sections in the study were obtained

photogrammetrically. Cross-section data at road and bridge crossings

were surveyed by the Soil Conservation Service. Survey creW assistance

was provided by Chaffee County and the town of Buena Vista. These

surveys were conducted during the period of January through March 1977,

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Watershed and drainage area mapS were developed from U, S. Geological

Survey topographic maps (scale i:62,500). Flood hazard areas are

plotted on photogrammetric maps prepared especially for this study_

Topography, planimetry, and cross-section data were compiled by photo-

grammetric methods from low level aerial photographY taken November 6,

1975. The photogrammetry is by Bell Mapping Company, 500 Kalamath,

Denver, Colorado, Funds for the mapping were provided by Chaffee County

with contracting for services through the Colorado Water Conservation

Board (CWCB). The maps were reproduced on a scale of 1"; 200' and

reduced to I" '= 400' for report purposes. Contour interval is 2-feet

and the datum is mean sea level. The map topography complies with
national map accuracy standards. Map mylars on a scale of I" ; 200' are

on file at the Soil Conservation Service, 2490 West 26th Avenue, Denver,

Colorado 8021], telephone [phone].

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Elevation Reference Marks

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During the winter and spring of 1977, several of the temporary reference

marks used for photogrammetric mapping were replaced with permanent

markers consisting of brass caps imbedded in concrete. This work was

done by survey crews employed by Bell Mapping Company. Survey notes of

the original horizontal and vertical control are on file with the Colorado

Water ConserVation BOard. Following Is a tabulation of the permanent

reference marks used for this study.

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Surveys

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Engineering fi.eld surveys for horizontal and vertical control Were

conducted by Bell Mapping Co. Horizontal control is based on the

Colorado State Coordinate System, Central Zone, established from U. S.

Department of Commerce, Coast & Geodetic Survey point ''winters'', The

vertical control is based on U. S. Coast and Geodetic Survey sea-level

datum of 1929. Field survey was conducted during the summer and fall

of 1975, prior to the aerial photography,

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