FLOOD06660 - Laserfiche WebLink

Home Browse Search

- 23 - ~- " " ~ f ~ ~ A sedimentation survey was made by the Soil Conservation Service at Castlewood Reservoir after the dam failed in 1933, This reservoir vIas located on Cherry Creek about four miles south of Franktown and was in operation for a 43-year period. The drainage area above the dam is 167 square miles. The survey showed a total accumulation of 708 acre-feet of sediment (an average of 16.5 acre- feet per year), The average sedimentation rate was computed to be 0.099 acre-foot per square mile per year. ~ i I , A sedimentation survey was made at Kenwood Reservoir in 1939 by the Soil Conservation Service. This reservoir was located at the present site of the Cherry Creek Dam about four miles southeast of Denver on main Cherry Creek. The period of record was only 3.25 years. The drainage area above the reservoir was 387 square miles, The survey showed a total of 378 acre-feet of sediment with an average sediment storage rate of 0,301 acre-foot per square mile per year, , ; In order to obtain data on sediment production from smaller drainages in this area, sedimentation surveys were made more recently on two smaller reservoirs, Englewood Reservoir and the Neugebaur stock pond. Englewood Reservoir is located a short distance west of the Franktovm-Parker Watershed on Little Dry Creek about one and one half miles north of the Arapahoe and Douglas County line in Arapahoe County. The survey of Englewood Reservoir was made by the Soil Conservation Service in 1956. The survey showed a total sediment accillQulation of 67 acre-feet for a twenty-year period and a sediment storage rate of 0,36 acre-foot per square mile per year. The sedirnentation survey of the Neugebaur pond was made by the Soil Conservation Service in 1955. This pond is located on a small tributary of East Cherry Creek at the upper end of the watershed. The survey showed a sediment storage rate of 0.40 acre-foot per square mile per year. ~ & I E t A sediment source map showing areas of low, moderate, and high sediment yields was prepared for the entire watershed area. For a portion of the area sedimentation rates had been deternlined by adjusting the data from reservoir sediment surveys to the hydrologic conditions prevailing during the period of record. Sedimentation rates were computed for the proposed reservoir sites by comparing conditions affecting sediment production in the areas having a knovffi sedimentation rate with the conditions in the drainage areas above the proposed sites, Where channel cutting and gully erosion were present, the amount of material eroded away was estimated; and an annual rate for this type of erosion was deterrQined using 100 years as the approximate time during which recent accelerated erosion has till<en place in this area. Present rates of sedimentation at the proposed reservoir sites were determined as varying from 0.144 to 0,360 acre-foot annually per square mile of drainage area, ~ i ~ .