FLOOD07222

• Designation Number: 329
• County: Adams
• Community: Commerce City
• Basin: South Platte
• Title: Flood Insurance Study - Commerce City, Colorado, Adams County
• Date: 12/1/1989
• Designation Date: 9/1/1992
• Floodplain - Doc Type: Floodplain Report/Masterplan

2.4 Flood Protection Measures

Wi th a history of major
Denver metropolitan area
which has resulted in the
a levee system along
(Reference 8).

flooding ion the South Platte River, the
saw a need for flood control structures,
construction of three major reservoirs and
portions: of the South Platte River

In 1950, Cherry Creek Dam WIIS constructed just upstream of Denver,
located approximatelY 13dvermihs from conunerce City, at a cost
of $20 million. The dam .is 14,300eeet long and 140 feet high.

During the 1950s, planning and desiign for the Chatfield Dam flood
controi reservoir on the South Plat'te River was completed; however,
funding was not available toinit'iate and complete cOnstruction.
Three hundred million dollars in droperty damage suffered in 1965
changed the minds of many, le~ding to project funding and
construction. In 1973, final clos~re of the dam was made and the
facility became capable of storing floodwater. Chatfield Dam is
located approximately 0.5 mile above the City of Littleton,
Colorado, in Douglas and Jefferson ;Counties, approximately 18 ri ver
miles upstream from Conunerce City.

In addition to the Cherry Creek aIld. Chatfield Dam, one additional
flood control measure, the Bear C~eek Dam, was envisioned in the
early 1940s. The Belir Creek Dam i~ located in Jefferson County, on
Bear Creek, approximately 16 rive~ miles upstream from Commerce
City. Authorization for funding and design of the dam did not occur
until 1968. Construction on thei$68 million earthfill structure
started in July 1974 and became operational in 1979. The dam is 170
feet high, approximately 7,000 feet 'long, and has a storage capacity
of 75,000 acre-feet, equivalent to the U.S. Army Corps of Engineers
(COE) standard project flood.

Throughout the study segment of th~ South Platte River. in Commerce
City, levees have also been constructed as II flood protection
measure. However, during floods approximating the 100-year
frequency or larger, the levees !are subject to overtopping in
several areas.

Some channel improvements have been made to Sand Creek, including
two drop structures which have some!effect in reducing velocity, but
there are nO existing structural flopd protection measures.

3.0 ENGINEERING METHODS

For the flooding sources studied in detail in the community, standard
hydrologic and hydraulic study methods 'iere used to determine the flood
hazard data required for this study. Flood events of a magnitude which

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