FLOOD02174

• County: Denver
• Community: Lakewood
• Stream Name: Dry Gulch
• Basin: South Platte
• Title: Major Drainageway Planning
• Date: 7/1/1979
• Prepared For: Denver
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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l7

VI BENEFIT-COST ANALYSIS

Summary

The Major Drainageway Plan presented in this report consists

essentially of planned facilities to convey the lO-year flood

without flood hazard, damage to properties, or inconvenience

to residents and motorists. In reaches where the channels are

obstructed, lO-year pipe systems are planned. Because of the

present urbanization along the drainage routes, no effort is made

to re-establish open channels.

The lOO-year flood will result in inundation, inconvenience, and

damage, even after the planned facilities are constructed. How-

ever, this event will be extremely rare, and minor flood flows

will be largely unnoticed in the basin.

An extensive analysis was made of the benefits and costs asso-

ciated with the different alternatives evaluated in the Phase A

Report. The values determined in that report were preliminary

and presumed to be accurate enough to allow comparisons between

alternatives. The values, benefits and costs of the present

Phase B report have been greatly refined and updated to April,

1979. The estimated costs of and benefits to be derived from

the construction of the master plan are presented in this report.

While the details of the original Phase A Benefit-Cost analysis

are not repeated here, a summary of the elements of the analysis

is presented.

The proposed plan complies with the directives of the UDFCD,

the City of Lakewood, and the City and County of Denver.

Determination of Flood Damages

An estimate was made of the dollar value of the damages which

would be caused by each of the 5-year, 10-year, 50-year and lOO-

year floods, under fully developed watershed conditions and with-

out channel improvement. This was achieved by evaluating the

anticipated flooding depths which would occur at each building

site. A summary of the damages is presented in Table VI-I.

Determination of Benefits
The construction of drainage facilities results in benefits to

the pUblic to the extent that damages caused by flooding are

reduced. The proposed Master Plan for Dry Gulch incorporates