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<br />. <br />. <br /> <br />I <br />~ <br /> <br />t <br /> <br />~ <br />f <br />, <br /> <br />o <br /><0 <br />~ <br />to <br /> <br />Cisco pits are small retention structures constructed by a crawler tractor equiped with a dozer <br />blade. Pits are constructed by the tractor scooping out a small basin and depositing the spoil <br />material on the downhill side in the fonn of a small dam. In some cases the tractor packs down <br />the dam portion with the tracks of the vehicle (Gifford, et ai, 1978). Average sediment storage <br />capacities for existing Cisco pits range from 6 cubic yards to 21 cubic yards. Average density <br />of Cisco Pits is 6 to 8 per acre. <br /> <br />The effect of the Cisco Pits is to retain runoff and sediment on site, and decrease runoff <br />velocities. The Cisco Pits result in increased infIltration, decreased runoff and runoff velocities, <br />increased on site sediment retention, and improved environment for plant growth, <br /> <br />5) Water Spreaders - Water spreading is a technique that involves the diversion of water <br />from arroyos or gullies onto the surrounding landscape through use of a system of dikes <br />(Gifford, 1975). The spreader system consists of a series of contour dikes from 3 to 5 feet in <br />height and ranging in length from 100 to 2000 feet aligned nonnal to the direction of land slope <br />and spaced so that the toe of one is a few inches lower than the top of the next lower one. The <br />dike may be constructed with the borrow pit on either side but usua11y it is on the downstream <br />side and the flow is so directed that it moves in one direction on the upstream side of the dike <br />and returns in a reverse direction through the borrow pit on the downstream side (peterson and <br />Melin, 1979), Water spreaders must be located on specific sites relating to soil minerology. <br />Additions of saline water could create "slick spots or saline flats" where establishment of <br />perennial vegetation would be very difficult. Water spreaders divert runoff from confmed <br />channels and spread it over a large area where it will inftltrate and release limited amounts of <br />sediment. . <br /> <br />The effect of water spreaders is to divert runoff, decrease runoff velocity, and spread water over <br />a large area where it will have a greater chance to inftltrate, <br />Water spreaders result in increased inftltration and evaporation, decreased runoff and runoff <br />velocities, and limited amounts of on site sediment retention. <br /> <br />6) Detention Dams - Detention dams are structures consisting of an earthen dike with an <br />outlet pipe which a110ws water detained in the sediment reservoir upstream of the dike to <br />discharge downstream at a controlled rate (BLM, 1978), <br />Detention dams have earthen emergency spillways located several feet higher in elevation than <br />the outlet pipe in order to discharge flows larger than the outlet pipe is capable of discharging. <br /> <br />Detention dams are designed to pass a 50 year recurrence interval stonn or greater with a 25 <br />year effective sediment storage capacity. <br /> <br />The effect of the detention dam is to retain runoff and sediment on site, increase inftltration, and <br />control peak flows. The detention dams result in increased inftltration, decreased runoff and <br />runoff velocities, increased on site sediment retention, and decreased peak flows. <br /> <br />37 <br />