FLOOD00126

• Designation Number: 459
• County: Clear Creek
• Community: Empire
• Title: Flood Insurance Study - Empire, Clear Creek County, Colorado
• Date: 6/1/1976
• Designation Date: 7/1/1997
• Floodplain - Doc Type: Floodplain Report/Masterplan

2.3 Principal Flood Problems

Both the West Fork of Clear Creek and Lion Creek flow through
Empire 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.

Flooding in Empire is primari Iy a function of the spring snowmelt,
or possibly snowmelt in conjunction with rain-on-snow. Summer
rainstorms appear not to be the major cause of flooding although
heavy hai I storms occasionally cause drifts of hai I that block
drainage paths and create some flooding.

Neither Lion Creek nor Bard Creek have been gaged at Empire, but
the West Fork of Clear Creek has been gaged above and below
Empire for periods of four and three years respectively. These
stream gages do not, however, provide a record of sufficient length
to analyze for flood frequencies.

2.4 Flood Protection Measures

No flood protection measures are presently in effect in Empire.
No credit was given to flood attenuation due to any of the
small lakes and reservoi rs above EmpJre because of thei r relatively
smal I capacities to store flood waters and the fact that they are
almost always ful I.

3.0 ENGINEERING METHODS

For streams studied In detai I within the City, standard hydrologic and
hydraulic study methods were used to determine the flood hazard data
required for this study. Floods having recurrence intervals of 10,
50, 100, and 500 years have been selected as having special significance
for the land use and flood insurance program. The analyses reported
here reflect both current and planned conditions in the watersheds
of the streams.

3.1 Hydrologic Analysis

Hydrologic analyses were carried out to establish the peak
discharge-frequency relationships for floods of the selected
recurrence intervals for each stream studied within the City.

For both +he West Fork of Clear Creek, Bard Creek, and Lion
Creek, f lood-f low frequency data were based on a reg i ona I 'hydro-
logic analyses set forth in a "Manual for Estimating Flood
Characteristics of Natural-Flow Streams in Colorado" (Reference 8).

7