Watershed Work Plan for Watershed Protection and Flood Prevention West Cherry Creek Watershed

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- 9 - The critical runoff and sediment source areas will be stabilized by the application of the following mechanical measures: Terracing, contour farming, check dams with pipes, and diversions. With such measures, plant cover will increase and less erosion and sediment damage will occur. These measures will be established in accord with Colorado State Engineer require- ments and State Water Law. The sponsors and assigned technicians will advise local farmers and ranchers in conformity with Colorado State Water J Law when assisting them. Land Treatment Measures for Flood Prevention The 5,184 acres of woodland and brushland is being protected from fire by the Colorado State Forest Service in cooperation with Douglas and El Paso Counties. The Black Forest, Monument, and Castle Rock Volunteer Fire Departments are cooperating fully with these agencies. Structural Measures for Flood Prevention A system consisting of three floodwater- retarding structures, eight combination grade stabilization and floodwater- retarding structures, and six stabilizing and sediment control measures will be installed. The three floodwater- retarding structures will be installed to further reduce floodwater and sediment damages that cannot be provided by land treatment measures alone. These floodwater - retarding structures will control the runoff from 30.44 square miles or 62.1 per cent of the watershed from a storm that can be expected to occur once in 25 years. Figure 2 shows a typical floodwater - retarding structure. The eight combination grade stabilization and floodwater- retarding structures will be installed to prevent further channel entrenchment and to maintain present high water tables in the meadow areas. They will also reduce the amount of floodwater and sediment damage to downstream areas. Four of the structures will control the runoff from 7.60 square miles from a storm that can be expected to occur once in 25 years. The other four structures will control the runoff from 5.52 square miles from a storm that can be expected to occur once in 10 years. Six stabilizing and sediment control measures will be installed to control gully headcuts in critical areas and to reduce damage to other structures and meadow lands from sedimentation. The locations of the structures are shown on the Planned Structural Measures Map, Figure 3. Data concerning the proposed structures are summarized in Tables 3 and 3A. Preliminary designs and cost estimates are based on field and reconnaissance surveys. Designs provide for 2:1 back slope and 4:1 front slope for the dams. Design criteria conform to experience with foundation, fill materials, and construction conditions in the area. The designs meet all minimum requirements of the Soil Conservation Service and are in accord with the Colorado State Engineer's requirements and applicable State Laws.