FLOOD10807 ‎(2)‎

• County: Statewide
• Community: Northeast Colorado
• Title: Notheast Colorado Emergency Managers' Association Hazard Mitigation Plan
• Date: 10/1/2003
• Prepared For: Cheyenne, Elbert, Kit Carson, Lincoln, Logan, Morgan, Phillips, Sedgwick, Washin
• Prepared By: Amec
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

of a 100-year flood occurring within any 30-year period is 26%. The chance of a 100-year flood
occurring in any 100-year period is approximately 63%.

Dam Failure Flooding
Dam failure is a unique source of flash flooding. It is mentioned here in the Hazard
Identification section because there are many dams within the planning area, and some have
failed in the past. Most notably, the 1973 failure of Latham Dam in Weld County resulted in a
Federal Disaster Declaration. There have been a total of 4 dam failures within the planning area;
3 within Weld County (Chambers Lake, 1907; and Prospect Dam, 1980 are the other two), and
one in Sedgwick County (Julesburg Reservoir, 1917).

The CO-OEM map below displays the location of Class 1 and Class 2 dams within the planning
area. Class 1 and Class 2 dams are those that have been identified as presenting a high and
moderate threat, respectively, should they fail. Dam Safety classifications are based upon the
amount of loss that is estimated to occur to life and property should they fail.

.

. ...
.

...

.

Dmns (hilJh and mollerale hMard)
... CI.t$$ 1
... Class2
Texl COUllty Nllmes.
D Countv bound..'h.!$

70

o

70

140 Miles

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Class 1 and 2 dams are required by state law to have Emergency Action Plans (EAPs) in place.
There are no official recurrence intervals calculated for dam failures. Within the planning area
there have been 4 failures between 1907 and 2003, a 95-year period. Thus one could infer that
dams have been failing within the planning area on the average of once every 24 years.

Blizzards and Severe Winter Storms
Heavy snow, ice, severe winter storms, and blizzards are common to northeastern Colorado.
With the exception of flooding, these hazards have caused more state and federal disaster
declarations than any other hazard. Technically, the National Weather Service defines the
following winter storm characteristics as follows:

Blizzard: Winds of 35 mph or more along with considerable falling and/or blowing snow,
reducing visibility to less than one-quarter mile for three or more hours. Extremely cold
temperatures often are associated with dangerous blizzard conditions, but are not a formal
part of the definition. The hazard created by the combination of snow, wind and low
visibility significantly increases, however, with temperatures below 20 degrees.

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