FLOOD06461

• County: Larimer
• Community: Estes Park
• Stream Name: Fall River, Lawn Lake
• Basin: South Platte
• Title: The Lawn Lake Dam Failure and the Fall River Flood
• Date: 8/6/1982
• Prepared For: FEMA
• Prepared By: Many
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

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PART II
BACKGROUND INFORMATION

A. HISTORY OF LAWN LAKE DAM

The Lawn Lake Dam, located approximately 10 miles northwest of
Estes Park, was constructed in 1902. Original storage and re-
charge rights were granted on March 18, 1912, for the contain-
ment of 759.6 acre feet of water. Lawn Lake was a natural lake
but its elevation was raised by the construction of the earthen
dam. The storage rights and dam are owned by the Farmer's
Irrigation Ditch and Reservoir Company of Loveland, Colorado.
The area of Lawn Lake was included within Rocky Mountain National
Park when the Park was established by Congress on January 26,
1915. The storage reservoir was used to supply irrigation re-
serves to agricultural producers of the high plains of northeast
Colorado during the summer growing season. It is estimated that
Lawn Lake contained approximately 817 acre feet of water at the
time of the dam failure.

B. DRAINAGE BASI~ HYDROLOGY AND ..~OODPROBLEMS

Estes Park is located at the confluence of the Big Thompson and
Fall Rivers. The town is surrounded by National park and Nation-
al Ibrest lands. The climate can best be described as high-
altitude and semi-arid with all the attending ramifications of
such a classification: sudden and violent thunderstorms, flash
floods, heavy upstream snowpacks, and the critical need for stor-
age reservoirs. Even though violent storms are frequent, the
National Weather Service stresses that the July 15 flood event
was not caused by meteorological conditions. (ATTACHMENT 4)
The Fall River through and above Estes Park is typical of mountain
streams. It has heavy vegetation along the banks of the channel,
a cobbled stream bed, large rock outcroppings, steep channel
slopes and has. the potential for high water velocities. The Fall
River drainage area at the confluence is 39.9 square miles. The
Big Thompson at this point drains 137 square miles.

The Fall River has a history of flooding. High streamflows have
been recorded in 1949, 1951, 1953, 1957, and 1965. Damages from
the 1965 event were the result of encroachment upon the river
channels and blockage of the river through the central business
district. The Big Thompson disaster of August 1976 was the last
major flooding in the area, but it did not directly affect Estes
Park in terms of physical damages. A previous dam failure in
the area occurred on May 25, 1951 when Lily Lake dam collapsed
causing flooding along Fish Creek, a direct tributary to Lake
Estes.

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