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I I I I I I I I I I I I I I I I I I I OOlilU2 The reach of Cherry Creek studied in thi s report 1 ies between the Arapahoe-Douglas County Line and Arapahoe Road, for a total distance of 2.2D miles along the valley. Figure-1 shows the total drainage area of Cherry Creek and the location of the study reach. 2. Climate The Cherry Creek basin climate is semi-arid. Warm summers and mild to cold winters occur. Intense thunderstorm rainfall, sometimes of cloudburst intensity. occurs during the summer months. 3. Dams and Reservoirs No maj or fl ood protect ion st ructures ex i st in the Cherry Creek basi n upstream of the study area. The Soil Conservation Service has completed construct ion of 32 floodwater retardi ng structures as part of the "Franktown-Parker Tributari es of Cherry Creek Watershed" and "West Cherry Creek Watershed" projects. The structures were constructed for desi gn fl oods havi ng a 25-year recurrence interval. These reservoirs generally affect only the normal flow on Cherry Creek and offer 1 imited flood protection downstream of the dams. The dams have little or no effect on major floods in Cherry Creek at Arapahoe Road. The Cherry Creek Dam was completed in 1953. This dam and reservoir control s the runoff from the 386 square mi 1 es of hi gh p1 ai ns catchment. The total storage capacity in the lake behind the dam is 228,400 acre-feet. The flood control storage is 70,960 acre-feet, the multi-purpose storage is 13,960 acre-feet and the surcharge storage is 134,500 acre-feet (Corps of Engineers. 1974). Water was first stored in the lake in 1957. 4. St ream fl ow A summary of available stream gaging records for Cherry Creek near Melvin is presented in the following paragraphs. In general, most of the disastrous floods in the Cherry Creek basin have been caused by intense thunderstorm rain- fall. Snowmelt augmented by general spring rains can a1 so produce serious -10-