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<br />rate of water transmission. Soils of the other study areas in San <br />Miguel County are Cryoboralfs-Rock Outcrop Associatione which are <br />classified by the SCS as Hydrologic Soil Group D (high runoff <br />potential). Vegetation in these areas consist of approximately 80 <br />percent dense trees and 20 percent bushes, which retard potential <br />runoff (Reference 5). <br /> <br />In the past, the prime economy of the county depended on mining and <br />agricultural activities. In recent years, many changes have <br />occurred within San Miguel County, certainly not the least of which <br />has been the development of a major ski resort near the Town of <br />Telluride. In addition, Colorado has become the center of a new <br />market for mountain homesites usually to be used as second homes. <br />As a result, the county has gradually moved toward a recreation- <br />based economy. <br /> <br />2.3 Principal Flood Problems <br /> <br />The only severe floods in the San Miguel River basin for which <br />definite information is available before 1948 were those of <br />September 5, 1909, and October 5, 1911. The flood in 1909 caused <br />the failure of two small Telluride Power Company power reservoirs <br />of the Telluride Power Company on Lake Fork of the San Miguel <br />River. The State Engineers, who made an investigation of these <br />failures, stated that the property damage caused by the flood was <br />"appalling." The flood in 1911 washed out railway tracks and <br />public roads, caused the failure of Trout Lake Dam, and the 10ss of <br />one life. The damage costs and recurrence intervals of the 1909 <br />and 1911 floods cannot be estimated because historical data are <br />sparse and of limited reliability. Floods also occurred in these <br />areas to a lesser extent in 1913, 1923, 1927, 1964, and 1966 in the <br />San Miguel basins. <br /> <br />Because Telluride lies on the alluvial fan of Cornet Creek, most of <br />the flood problems in the Town of Telluride are caused by this <br />creek. Flood hazards are due primarily to mud and debris flows. <br />The upper portion of the Cornet Creek watershed consists of <br />',olcanic rock. Glacial erosion has left the south and southwest <br />facing walls of Mount Emma, the St. Sophia Ridge, and Mednota Peak <br />in a very steep and unstable condition. These walls are the <br />primary source for mud flows. Heavy rainfall, especially when <br />accompanied by saturated ground surface conditions, serves as the <br />starting mechanism for downslope movement of debris on these walls. <br /> <br />Two of the most destructive mud and debris flows occurred during <br />the floods of July 27, 1914, and August I, 1969, which were caused <br />by heavy rainfall preceded by a period of wet weather. It is <br />likely that the flood was caused by large boulders and debris <br />jamming the the narrow channel of Cornet Creek at various locations <br />during the flood descent. During the cloudburst flood of July 27, <br />1914, as described in the San Miguel Examiner, a river of mud, its <br />height very conservatively estimated at between 8 and 10 feet in <br />height, swept out of Cornet Creek Canyon just north of the Town of <br />Telluride and swept away everything in its path. The loss 'was <br /> <br />6 <br />