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

FLOOD POTENTIAL - FUTURE CONDITIONS

Reach Flood Hazard Area Cross Sections
Number Map-Sheet Numbers Designations
4 1, 3, 5'& 6 I, EA thru EZ, FA thru FB, BP
5 1, 2, 3, 4, & 6 X, GA thru GO, BM

The effects of watershed land Use changes anticipated within the next 10

to 20 years were .analyzed in relation to future flood heights. Infor-

mation regarding land use and expected developments were obtained from

Typical Valley Cross Sections

the "Chaffee County Comprehensive Plan-1976" prepared. by the Upper

Arkansas Area Council of Governments and Chaffee County. Comparison of

present and future runoff data showed insignificant differences from

Cross-sections for each stream are designated alphabetically, starting

from the downstream end of each study reach. The following order has

projected changes in land use, Rationale for these results are:

been used: Section A, B, .

Y, Z, AA, AB, etc. The designation

(1) Potential developments are located in the lower reaches of the

sequence is unique for each reach. With the exception of starting and

watershed where a slight amount of additional runoff has a minor effect

another.

on the magnitude of major flood flows (i.e_, the 100-year frequency
flood), and (2) the major portion of runoff originates in the San Isabel

end points, the designation is not carried over from one reach to

National Forest where a small amount of land use change is anticipated.

Exhibit B is a selection of typical valley cross-sections illustrating

the configuratioh of stream channels and adjoining flood plain areas.

Of upmost importance is the possibility of encroachment on the existing

flood plains. Developments within the flood plain could obstruct the

Shown on the cross-sections are the elevations and lateral extent for

the 100- and 500-year flood events.

flow of flood water, raise the flood elevations, and create hazardous

velocities. Encroachment is a far more significant factor than the

Flood Frequency-Elevation and Discharge Data

additional runoff created by proposed upstream developments.

discharges for the 10-, 50-, 100-, and 500-year floods. Tabulated

The National Flood Insurance Act of 1968 (Title XIII of the Housing and

Urban Development Act, P.L. 90-448) recognized the necessity. for flood

Table 1, pages 1 thru 18, include flood crest elevations and peak

information is intended for use in conjunction with the water surface

plain management. This act makes federally subsidized insurance avail-

profiles and flood hazard area maps. The information is compatible

able to citizens in communities that adopt regulations controlling

with reach numbers and cross-section designations.

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