FLOOD09565

• 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

f

On July 15, 1982, the dam for a pr ivately owned reservoir
known as Lawn Lake located in Rocky Mountain National Park failed
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 which were 2.5 times the
estimated depth of a 500-year flood. . Lake Estes, located on the
Big 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 million, were revised to about $31
million. This event is the fifth most severe 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 major 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 Lake flood was not the
first time a dam failure flood had impacted the Estes Park area.
On May 25, 1951, Lilly Lake Dam on Fish Creek, a tr ibutary 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 killed in a single
flood event is 139 lives lost during the Big Thompson Canyon
flood of July 31, 1976. At least 314 people have been killed
from floods since Colorado became a state. 'rhe most damag ing
flood occured in June 1965 when almost $500 million in property
was lost in the Denver metropolitan area. Cumulative flood
losses since statehood are estimated to be over $1.6 billion
dollars at present value.

;

Floodprone areas have been identified in 212 c it ies 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
billion dollars. Only about 9 percent of all structures 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 potential for
higher flood damages.

~

ix