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8 inches at Delta and 13 inches in the COlona-Ridgway area to as much as 40 inches in the mountainous areas, with approximately 30 to 40 percent of the precipitation being from snowfall (Refer- ence 3). The frost-free period averages approximately 127 days annually, and varies from 112 days at higher elevations to 148 days in the valleys. The elevations in this region range from 7,000 feet to 7,485 feet. The soils vary in depth, with coarse grained, mostly of alluvial origin, in the valley, to heavy rocks on the drainage slopes. The vegetation in the Uncompahgre River Basin ranges from desert shrubs in lower valleys to alpine plants in the river headwaters. Development within the detailed study reach has been limited to the areas in and near the Town of Ridgway with the exception of ranch-type dwellings and buildings in the wider valley of South Ridgway. Lately, some mobile homes have been located in the wider valley west of U.S. Highway 550, which parallels Uncompahgre River. Because of its centralized location, Ridgway has historically been a commercial service center. Initially serving railroad related activities, it now serves the recreational and tourist industries. 2.3 Principal Flood Problems Uncompahgre River located in Ridgway has little serious flooding potential. In fact, no newspaper articles or other historical records were found to document severe flooding of Uncompahgre River at Ridgway. The earliest reference to flOOding on Uncompahgre River is contained in the U.S. Geological Survey's Water Supply Paper 997 (Refer- ence 4). In reference to the widespread flooding which occurred during the spring and early summer of 1884, it states "the melting of the heavy snowfall of the winter of 1883-84 caused the highest flood known on the Colorado and Gunnison Rivers, in June 1884, and undoubtedly caused similar flooding on the Uncompahgre River. The only available reference to such a flood, however, is an item in the San Juan Prospector of May 17, 1884, which states that 'Uncompahgre is rising rapidly and an overflow is feared'." Floodflows on Uncompahgre River within the study reach result from the rapid melting of the mountain snowpack during the period from May to early July. Snowmelt may occasionally be augmented by rain. The runoff from snowmelt typically sustains periods of hig~ flows and marked daily fluctuation. Although summer cloudbursts are a flood threat to occupied areas at the mouth of tributaries of Uncompahgre River, examination of streamflow records reveal that the cloudbursts are not a flood threat to the main channel. All streams tributary to Uncompahgre River within the study area drain minor areas, and while many are subject to cloudburst-type 4