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. Climatic conditions are characteristic of a high altitude, dry continental climate. Sixty-seven years of recorded temperatures at Idaho Springs indicate a high of about 92 degrees, a low of -32 degrees, and an average annual temperature of 43.4 degrees Fahrenheit. The normal annual precipitation in the higher altitudes is in excess of 35 inches and about 16 inches at Georgetown and Idaho Spri ngs. Vegetation varies throughout Clear Creek County watersheds. In areas above timberline, there are many rock outcroppings and the steep mountain slopes are practically void of vegetation. In the timber and woodland areas, aspen, spruce, and pine stands pre- dominate. Because of the steep mounta ins lopes and narrow va II eys In C I ear Creek County, development has by necessity occurred near the streams and often within the flood plain. County roads, state and interstate highways cross the flood plains and often con- strict the free flowing streams with bridges and embankments. Continuing development within the study area is expected, and pressures leading to intensified flood plain use wi I I probably accompany such development. 2.3 Principal Flood Problems Streams in Clear Creek County flow in narrow channels with relatively steep slopes. Large flows through the County are characteriz~d by very high velocities and unstable water surface elevations. Bridges appear to be the greatest constraints on passage of flood flows. Flooding in Clear Creek County is primari Iy a function of the spring snowmelt, or possibly snowmelt in conjunction with rain-on-snow. Summer rainstorms do not appear to be the major cause of flooding although heavy hai I storms occasionally cause drifts of hai I that block drainage paths and create some flooding. Clear Creek has been gaged within Clear Creek County near Lawson (29 years of record), below Idaho Springs (4 years of record) and at Idaho Springs (2 years of record). The West Fork of Clear Creek has been gaged above Empire (4 years of record) and near Empire (3 years of record) and Fal I River has been gaged near Idaho Springs (9 years of record). Clear Creek is also gaged below the County near Golden (64 years of record). . The stream gage located near Lawson recorded a flow of 6,130 cubic feet per second (cfs) fol lowing the 1956 fai lure of the Georgetown Lake Dam. The maximum known flood at the gage near Golden was esti- mated to be 8,700 cfs in 1888. 8 , J'J