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also occupy the narrow valley adjacent to the stream. grades are considerably above the stream banks and are high velocity flood flows by riprap. Most highway protected against c. As the stream passes from the mountains to the plains at Morrison, the economic characteristics of the valley change from the mountain influence to the influences of metropolitan Denver. For this reason, urban encroachments started near the mouth of Bear Creek near Denver and proceeded up the valley toward Morrison as metropolitan expansion continued. Presently, concentrated metropolitan expansion has occurred in the lower 4 miles of the valley, to Wadsworth Avenue. Growth patterns indicate continued rapid urban expansion toward Morrison, OJ an additional stream distance of about seven miles. The portion of the valley not currently urbanized is devoted principally to pasturage. . III. HYDROLOGY 8. CLIMATOLOGY ~ The climate of the Bear Creek basin is influenced by the wide range of topographic elevations. For this reason, the climate varies from sub-humid in the mountain portions to semi-arid in the plains areas. Long, cold winters with heavy snow accumulations typify the mountain regions, whereas in the plains region temperatures fluctuate from cold to mild. Heavy snow accumulations in the plains areas are unusual, since snowfall usually melts during the intervening periods of mild weather. In spring and summer, the cooler temperatures of the mountain elevations normally cause a gradual melting of the snowpack, which increases streamflow from late spring to midsummer. 9. RUNOFF AND STREAMFLOW DATA a. Runoff. Runoff in the Bear Creek basin occurs principally from snowmelt in the mountain portions of the basin. Rapid rises in runoff occur principally from intense rainstorms centered over portions of the basin. Rainstorm runoff is typically of the flash-flood variety. How- ever, general rains on snowpack produce floods of larger volume and duration. The average annual runoff in the basin ranges from one inch in the high plains region to five inches in the mountains. b. Streamflow. Discharge records of Bear Creek are available at two gaging stations operated by the Colorado State Engineer. The gaging station at Morrison with a drainage area of 164 square miles, has 55 years of record, and the gaging station at Sheridan, with a drainage area of 260 square miles, has 38 years of record. The peak discharge of record at the Morrison stations was 8,600 cubic feet per second on 24 July 1896, and at the Sheridan gaging station, was 3,000 cubic feet per second on 7 July 1933. The long term average daily discharge is approximately 55 cubic feet per second at the Morrison gaging station and 35 cubic feet per second at the Sheridan gage. 35 96-1260-fiB-:.