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. Introduction On July 15,'1982, at about 5:30 a.m., the privately owned lawn lake Dam located within Rocky Mountain National Park, about 60 miles northwest of Denver, Colorado, failed. Flood damage occurred in a 13 mile reach from the lawn lake Dam to lake Estes which is located about 1 mile downstream from the heart of the resort community of Estes Park. The flood claimed the lives of three people camped within Rocky Mountain National Park and also caused extensive property damage in and near Estes Park. This paper examines the lawn lake Dam failure, specifically the discovery of the failure, the movement of the flood from lawn lake Dam to lake Estes, the decision to evacuate the public, implementation of the flood warning, and public response to the warning. The success of the warning and evacua- tion is evaluated and factors that operated for and against the success of the evacuation are discussed. Finally, a discussion on how the lawn lake experience may be used to re~uce the impacts of future dam failure is given. We begin by briefly describing the physical setting of lawn lake, the location of populations at risk in this setting, the sequence of flood events, and the damages resulting from the flood. This is followed by a description and evaluation of the flood warning and public response. , Setting lawn lake originally was a natural lake within' Rocky Mountain National Park (see map, fig. 1). About 1903, before the National Park was estab- lished, 'an earthen dam was constructed to increase the storage at lawn lake. The dam was later raised. At the time of failure, the dam was owned by Farmers Irrigation Ditch and Reservoir Company of loveland, Colorado. The earthen dam impounding lawn lake was nearly,11,OOO feet above sea level and about 4 air miles from the nearest road' (Endovalley Road). Records kept by the Colorado State Engineer indicate that the dam was 24 feet high and had a water storage capacity of, 817 acre-feet. Water passing through lawn lake Dam traveled the Roaring River into Fall River and then into the Big Thompson River before entering lake Estes, about 13 miles downstream from lawn lake Dam. The Roaring River drops about 2,500 feet in a narrow 4-1/2 mile reach before entering Fall River. From the mouth of Roaring River to Cascade Dam, which is owned by the town of Estes Park, the Fall River channel traverses a much wider and flatter flood plain known as Horseshoe Park. In this distance of about 2-1/4 miles the drop is less than 100 feet. Downstream from Cascade Dam the flood plain again narrows and the elevation drops about 1,000 feet in 6-1/2 miles. The number of people at risk of personal injury upstream from Cascade lake Dam was quite small. There were about 25 to 30 people camped either at lawn lake or at campsites dispersed along the banks of Roaring River. There are normally only a few people within Horseshoe Park during the time that the flood occurred, either fishing or driving on Highway 34 or Endovalley Road. Therefore, in the first 6-3/4 miles downstream from the