The Lawn Lake Flood

Lawn Lake is a natural lake, 11,000 feet high in the mountains of what is now Rocky Mountain National Park (RMNP) above the town of Estes Park. It was reputedly named by a hiking party from MacGregor Ranch in the 1880s for its natural lawn-like shores. In 1903, a group of farmers from Loveland, the Farmer’s Irrigation Ditch and Reservoir Company, enhanced the natural lake from 16.4 acres to 48 surface acres. The lake was as deep as 35 feet in some places. Water from Lawn Lake irrigated crops in the Loveland area for years.

Although Lawn Lake was used to irrigate crops for years, the dam fell out of maintenance because of the six-mile hike that was required to service it. There had been a road to Lawn Lake when the dam was being built, it was long since gone by 1982 and no vehicles or heavy equipment could reach the dam. These factors reduced the frequency of inspections. Over the years of neglect, a leaky outlet pipe on the upstream side of the dam wore away at the dam’s structure. Lawn Lake dam was headed for collapse.

The morning of July 15, 1982, was bright and sunny. No clouds threatened overhead, and no one in Estes Park that day would have imagined that a devastating flood was about to overwhelm the town. Shortly after 5:30 a.m., Lawn Lake dam broke, letting loose 674 acre-feet of water down the Roaring River. A backcountry camper was killed as he slept in his tent along the river. Surviving campers along the Roaring River estimated the wall of water to be 25-30 feet high coming down the valley.

When the water reached Horseshoe Park, the churning mass slowed down and deposited much of the debris it has picked up on its six-mile rampage, leaving an alluvial fan of huge boulders and debris. The flood water was temporarily contained when it hit the flat, wide floor of Horseshoe Park. Muddied water overran Aspenglenn campground, a popular destination in Horseshoe Park. Rangers had enough time to warn people to evacuate, but two campers were killed in the campground when the course of the flooded Fall River suddenly changed.

The flood water flowed into Cascade Lake, a man-made lake built by F. O. Stanley in 1909 to store water to run his hydroelectric plant, located about a mile downstream. Although the Cascade Lake dam held for a while, it was soon worn down by the four feet of water that flowed continually over its rim. Finally the second dam broke, sending 18,000 cubic feet per second of water down the Fall River, on a collision course with Stanley’s hydroplant and with downtown Estes Park. On an average summer day today, about 100 cubic feet per second flows in the Fall River through town.

 
The furious water hit the plant with a great rage. It picked up boulders and trees, which acted as battering rams. Flood water picked up the garage that stood upriver and smashed it into the plant. The water and debris knocked out the supports from under that largest section of the plant. The floodwater also destroyed the penstock, which had carried water from the Cascade Lake dam to the hydro machinery to produce electricity. Only the heavy equipment inside the plant saved it from being entirely washed away. The plant would never operate again.

F.O. Stanley’s hydroplant was the first building to fall victim to the flood. After the water devastated the plant, the Department of Wildlife’s fish hatchery was similarly destroyed, wiping out 90,000 fish in the rearing ponds. The slow-moving mass of mud and debris then flowed down Elkhorn Avenue, carrying camper vans and mobile homes with it and causing huge amounts of damage to the shops along Estes Park’s main street.

The floodwater eventually met up with the Big Thompson river and flowed into Lake Estes. Olympus Dam, at the eastern edge of Lake Estes, was strong enough to hold back the flood water and the wave of destruction was halted, even though the level of the lake rose by two feet. In less than four hours, three people were killed and $31 million in public and private damages, cleanup, and economic loss were incurred.

For more of the story of the Lawn Lake Flood, click HERE.