Lawn Lake Dam was an earthen

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

that failed on July 15, 1982, at about 6 a.m., in an event known as the flood of 1982. The sudden release of 30 million cubic feet (849,000 m³) of water resulted in a flash flood that killed three people camping in the park and caused $31 million in damage to the town of

Estes Park, Colorado Estes Park is a statutory town in Larimer County, Colorado, United States. The town population was 5,904 at the 2020 United States Census. Estes Park is a part of the Fort Collins, CO Metropolitan Statistical Area and the Front Range Urban Cor ...

and other downstream areas.

Lawn Lake

Lawn Lake was originally a natural lake with a surface area of 16.4 acres (6.6 ha), located at an elevation of approximately 11,000 feet (3,400 m) in the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico ...

. In 1903 a group of farmers from Loveland built a dam to increase it to a surface area of 48 acres (19.4 ha) for the purpose of providing water for irrigation in Loveland.

Dam failure

Over the years the road that had been cut to permit construction of the dam fell into disrepair and ceased to exist. Because of the dam's remote and difficult location, inspection and repairs lapsed. The Colorado State Engineer determined that the probable cause of the dam failure was deterioration of lead caulking on the joint between the outlet pipe and the gate valve leading to internal erosion of the earth-fill dam. There had been issues reported during inspections in 1951, 1975, 1977 and 1978. When the dam failed the waters rushed down the Roaring River valley, which falls in , at a peak rate of 18,000 cubic feet per second (510 m³/s), scouring a large gully out of the mountain stream and killing one person camping alongside it. At this rate, the lake emptied in about half an hour. When the waters reached the broader valley of

Fall River Fall River is a city in Bristol County, Massachusetts, United States. The City of Fall River's population was 94,000 at the 2020 United States Census, making it the tenth-largest city in the state. Located along the eastern shore of Mount H ...

at Horseshoe Park they spread out and slowed, leaving behind a large

alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but a ...

of debris. The flood continued down Fall River and hit the Cascade Dam which stored water to run a hydroelectric plant about a mile (2 km) downstream. Cascade Dam failed from the onslaught and added its waters to the flood. The Aspenglen campground was destroyed and two campers who returned to recover camping gear lost their lives, due to insufficient warning from park rangers. The flood entered the town of Estes Park and caused severe damage to 177 downtown businesses (75 percent of Estes Park's commercial activity). In Estes Park the flood joined the

Big Thompson River The Big Thompson River is a tributary of the South Platte River, approximately 78 miles (123 km) long, in the U.S. state of Colorado. Originating in Forest Canyon in Rocky Mountain National Park, the river flows into Lake Estes in the town ...

and flowed into

Lake Estes Lake Estes is a reservoir in Estes Park, Colorado created by Olympus Dam. The lake has a shoreline of about and a surface area of . The reservoir lies on the Big Thompson River The Big Thompson River is a tributary of the South Platte River ...

on the eastern edge of the city.

Olympus Dam Olympus Dam is a dam located on the Big Thompson River, in the town of Estes Park, Colorado Estes Park is a statutory town in Larimer County, Colorado, United States. The town population was 5,904 at the 2020 United States Census. Estes Park i ...

, part of the Colorado-Big Thompson Project, there withstood the deluge and the flood was halted.

Aftermath

The scar left by the scouring of Roaring River and the alluvial fan at Horseshoe Park are still very apparent 37 years later and will remain for a very long time . Twenty-five years after the accident, the extent of the former reservoir is still clearly evident, and at the mouth of the lake, the start of the Roaring River flows through the location of the former dam. As a consequence of the dam failure, aging dams at Pear Reservoir, Bluebird Lake and Sandbeach Lake in the park were demolished and removed.High Elevation Dam Removals in Rocky Mountain National Park

References

* Hydrology, Geomorphology, and Dam-break Modeling of the July 15, 1982, Lawn Lake Dam and Cascade Lake Dam Failures, Larimer County, Colorado. {{Authority control Dams in Colorado Buildings and structures in Larimer County, Colorado Buildings and structures in Rocky Mountain National Park Dam failures in the United States Disasters in Colorado Estes Park, Colorado 1982 in Colorado 1982 disasters in the United States 1903 establishments in Colorado 1982 disestablishments in Colorado Former reservoirs