FLOOD03000

• County: Statewide
• Stream Name: South Platte
• Basin: South Platte
• Title: Water and Related Land Resources Management Study Volume V - Appendix H
• Date: 7/14/1980
• Prepared For: South Platte and Tributaries
• Prepared By: CWCB
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

.

A combination of modifications at Kelly Road Dam with an
additional dam at the Upper Lowry site that would provide Kelly
Road Dam with a capability of storing floods up to the level of
the standard project flood would cost about $ll.3 million and the
benefit-cost ratio would be 2.0. Total average annual benefits
would be about $l.6 million and average annual net benefits would
be $809,000.

CHANNEL IMPROVEMENTS

Four channel improvement designs were evaluated for the area

downstream from Kelly Road Dam. These designs were for the 5-,

10-, 25-, and lOO-year floods. Costs would be $6.l million, $6.7

million, $8.5 million, and $l3.l million, respectively.

Benefit-cost ratios would be l.5, l.5, 1.2, and 0.8, respec-

tively. Net benefits would maximize at about the 5-year design

level; however, the lO-year design would provide a greater level

of protection at almost the same benefit-cost ratio. For all

levels of protection greater than the lO-year level, costs would

increase sharply because of the substantial number of residences

that would have to be acquired for necessary rights-of-way.

Total costs for a la-year design channel would be about $6.7

million. The channel would be approximately l.8 miles in length

and would consist of a combination of open channel and culvert

construction. Average annual benefits would be $704,000.

IMPROVEMENT OF DRAINAGE FACILITIES

Several means of improving the drainage capabilities of the

area upstream from Lowry Air Force Base were considered. There

are three detention ponds that provide storage in this area. The

2l

.
,
'.>