FLOOD00850

• Designation Number: 31
• County: Arapahoe
• Community: Unincorporated Arapahoe County
• Title: Major Drainageway Planning - Little Dry Creek, Report, Volume I
• Date: 2/1/1974
• Designation Date: 6/1/1974
• Floodplain - Doc Type: Floodplain Report/Masterplan

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SYNOPSIS

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Existing urban improvements along the Little Dry Creek drainageways are

subject to frequent flood damage. Continuing urbanization of the area

will result in more flood plain encroachment and greater future flood

damage unless positive action is taken to halt such encroachments.

Flood plain zoning is clearly the most economical and satisfactory way

to stop further flood plain encroachment, and such zoning should be

effected as soon as possible.

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Improvements that presently encroach on the flood plains require protec-

tion from flood flows. Most of these vulnerable improvements can be

given a high degree of protection by improving the major Little Dry Creek

drainageways. Proposed improvements include channelization, closed con-

duits, and the improvement and construction of flood detention dams.

Grass-lined and concrete-lined channels can be used to reduce flood plain

widths. Conduits can be used to convey flood flows underground. The ex-

isting Englewood Dam effectively reduces downstream flood discharge peaks,

but it requires extensive improvement to meet present safety standards.

Similarly, improvements are proposed to existing Blackmer and Quincy dams.

The new Holly, Berry and Prentice dams are proposed to provide additional

flood-peak-reducing detention capacity.

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A number of drainageway improvement plans were studied, ranging from the

minimum development of improving only Englewood Dam to far more extensive

development including channelization, conduits and a number of dams. The

proposed drainageway improvement plan selected by the Urban Drainage and

Flood Control District and the five participating local governments includes

improving Englewood Dam; raising and improving Blackmer and Quincy dam;

building Holly, Berry and Prentice dams; extending Cinderella conduit; and

channelizing parts of Little Dry Creek and Greenwood Gulch.

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The estimated cost of the proposed improvements is $7,164,000 in 1973 dol-

lars. The estimated ratio of benefits derived from the project to costs

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