FLOOD09157

• County: Statewide
• Community: State of Colorado
• Basin: Statewide
• Title: Flood Hazard Mitigation Plan for Colorado
• Date: 1/1/1983
• Prepared For: State of Colorado
• Prepared By: CWCB
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

Executive Summary

On July 15, 1982, the dam for a privately owned reservoir
known as Lawn Lake located in Rocky Mountain Nat ional Park fa iled
and released approximately 800 acre-feet of water down Roaring
River, Fall River, and the Big Thompson River. Flood waters rip-
ped through the National Park, Larimer County, and the Town of
Estes Park at depths of 10 to 12 feet wh ich were 2. <; times the
estimated depth of a 500-year flood. 'LakE' Estes, located on the
Biq Thompson River just below the town, rose 2.0 feet and pre-
vented any further damages to canyon residents.

Three persons were killed and one is still missing. Damages
initially estimated at $21 milli.on, were revised to about $31
million. This event is the fifth most se,vere flood in Colorado
recorded history, On July 22, 1982, the President issued a Major
Disaster Declaration for Larimer County.

In the past 20 years, there have been a total of eight pres-
idential major disaster declarations due to flooding in
Colorado, The Lawn Lake incident is only the second time a flood
due to dam failure in Colorado has been declared a major disaster
by the President. In 1973, thE! Lower Latham Reservoir dam in
Weld County failed and caused ma:ior flood damages in the Town of
Kersey.

There are 120 federal and 2,129 non-federal dams, or a total
of 2,249 high, moderate, and low hazard dams in the State of
Colorado. Since 1890, there have been at least 130 known dam
failures in Colorado. The recent Lawn I,ake flood was not the
first time a dam failure flood had impactE!d the Estes Park area.
On May 25, 1951, Lilly Lake Dam on Fish Creek, a tributary of
Lake Estes, failed and caused considerable damage.

Between 20 and 30 major floods occur somewhere in Colorado
every year. The largest number of people killE,d in a single
flood event is 139 lives lost during the Big 1'hompson Canyon
flood of July 31, 1976. At least 314 people have been killed
from floods since Colorado became a state. 'l'he most damaging
flood occured in June 1965 when almost $500 million in property
was lost in the Denver metropolitan area. Cumulative flood
losses since statehood are est imated to be over $1,6 b ill ion
dollars at present value.

Floodprone areas have been identified in 212 cities and
towns and in all 63 Colorado counties, Approximately 150,000
people, or about 5 percent of the state's permanent population,
are now believed to be living in the floodplain. The total value
of property exposed to flood hazard is estimated to be over 6
b ill ion dollars. Only about 9 percent of all struct ures in the
floodplain are insured and the amount of coverage is estimated to
be only about 7 percent of the value of the exposed property. As
the population of the state grows, so grows the potent ial fa 1:'
higher flood damages.

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