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San Miguel River, which was studied by detailed methods, has its headwaters in the Uncompahgre National Forest, approximately 50 miles upstream of Naturita. San Miguel River flows northwesterly from its origin near the City of Telluride through Naturita to its confluence with Dolores River, approximately 20 miles downstream of Naturita. The area drained by San Miguel River at Naturita is approximately 1080 square miles. The drainage basin of San Miguel River drops from an elevation of 13,500 feet at its headwaters to 5,430 feet at Naturita. Tributary 1 has its origin in the mesa south of town and flows northerly as an arroyo through Naturita until its confluence with San Miguel River just upstream of State Highway 97. The tributary has a drainage area of approximately 1.26 square miles at its mouth. Most of the San Miguel River basin is located within the eastern part of the Canyon Lands section of the Colorado Plateaus physio- graphic province, an area of plateaus underlain by relatively horizontal rock layers cut by deep canyons. The topography of the Naturita area consists of the long, narrow, gently sloping San Miguel Valley, which is surrounded by steep mesas north and south of the town. The climate of Naturita is semiarid with approximately 12.5 inches of annual rainfall. August is the wettest month and February is the driest month. The temperature ranges from an average high in the mid 70soF in July to an average low in the mid 20soF in January (Reference 2). The soils in the study area are stony and are derived from sand- stone and shale. They are characterized as light colored, loamy, and shallow (Reference 3). The study area is covered with a variety of pines, oak brush, and grass. 2.3 Principal Flooding Problems There are three principal causes of flooding on San Miguel River in the study area: rapidly melting snow during the spring; rain- fall on melting snow, which increases the melting process and, therefore, increases floodflows; and general rain floods, caused by prolonged rain over large areas. A search of historic records shows that floods occurred on San Miguel River in 1909, 1911, and, most recently, in 1942 (Reference 4). The September 5, 1909, flood was caused by severe rains on the headwaters of San Miguel River, which caused the failure of two small power reservoirs of the Telluride Power Company. Middle Reservoir failed on September 5, 1909, and a sudden release of 4