FLOOD10684 ‎(2)‎

• County: Clear Creek
• Community: Clear Creek County and Unincorporated Areas
• Title: FIS - Clear Creek County and Incorporated Areas
• Date: 3/19/2007
• Prepared For: Clear Creek County
• Prepared By: FEMA
• Floodplain - Doc Type: Current FEMA Regulatory Floodplain Information

boundaries is approximately 0.25 square miles. The 2000 U.S. Census reported
the population of Silver Plume as 203 (Reference 4).

2.3 Principal Flood Problems

Major flooding has occurred throughout the area studied by detailed methods in
Georgetown. A flood occurred along Clear Creek at Rose and 10th Streets on
June 9, 1864. A levee was constructed the following day to keep the stream
within its limit. This levee is no longer in existence. Another flood occurred
following three days of heavy rainfall ending on July 23, 1965, when water
spilled out of its bank at three locations along South Clear Creek and an area
from Main to Rose and 8th and 11 th Streets was inundated. A snowmelt flood
occurred along Clear and South Clear Creeks in June 1983 (Reference 1).

Clear Creek (both in Idaho Springs and Silver Plume), Soda Creek, Virginia
Canyon, and Chicago Creek flow through Idaho Springs in narrow channels with
relatively steep slopes. Large flows through the city are characterized by very
high velocities and unstable water-surface elevations. Bridges appear to be the
greatest constraints on passage of flood flows.

Deposition of large amounts of sediment, including sand, gravel, and small
boulders, has occurred at the base of steep mountain gulches in Idaho Springs
following heavy runoff periods. These deposits occasionally cover roads and
affect flooding in the manner that a permanent alluvial fan would affect flooding.
Gilson Gulch and the Gulch above 8th Avenue are affected in this manner.

Clear Creek has been gaged at two locations within Idaho Springs for periods of
2 and 4 years. Neither station had a record of sufficient length to analyze for
flood frequencies.

A search of available data revealed that no significant flooding has occurred in
Idaho Springs. The largest flow through Clear Creek that could be found
occurred in 1956 due to the failure of the Georgetown Lake Dam. It is estimated
that flood flows recorded on Clear Creek through Idaho Springs were
approximately 5,500 cubic feet per second (cfs) from that dam failure.

Research has revealed that there has been no significant flooding inside the
corporate limits of Silver Plume.

Flooding in Georgetown, Idaho Springs and Silver Plume is primarily caused by
either spring snowmelt or snowmelt in conjunction with rainfall. An exception to
the usual pattern of flooding is that heavy hailstorms occasionally cause drifts of
hail that block drainage paths and create some minor flooding.

2.4 Flood Protection Measures

There are no existing flood control structures presently in effect in the County.

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