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the trench and partially buried roll will act as asemi-permeable water and sediment trap, <br />serving to provide an improved growth zone on steep dry slopes. Once rows of vegetation <br />ace established they may be expected to create their own habitat and continue to invade the <br />slope. As the rolled blanket deteriorates over time, the vegetation will effectively replace it. <br />Level Spreader <br />A level spreader is a level section of ditch that is used to pool water at the end of a ditch, <br />diversion, or channel. The pool formed by the spreader transforms small concentrated <br />flows into sheet flows when it overflows (Figure C-4). Sheet flow is less erosive than a <br />concentrated flow and it may be used to irrigate vegetation. The gradient of the level <br />spreader ditch must be 0%. The ditch should beat least 6 inches deep and 6 inches wide at <br />the containment level. The lip of the spreader should be of non-erodible material or be <br />protected with erosion control blanket or gravel mulch (Figure C-5). The strucuue should <br />be inspected and maintained offs significant runoff events. Spreaders help to prevent <br />erosion and improve soil moisture content which in taro improves plant growth. <br />Terracing <br />The slope and length of a hillside combined with soil physical characteristics affect its <br />stability. The longer a slope becomes the more susceptible it is to water erosion. Hillsides <br />of equal slopes and lengths, but with different soil physical characteristics will erode at <br />different slope distances. Terraces may be used to limit slope length and effectively control <br />erosion and sedimentation (Figure Chi). Terraces can be built on the level and adequately <br />sized to provide total contaimnent for the slope that drairs to them. They can also be placed <br />on low gradient slopes and drain to nxonstnrcted channels. Terrace spacing will be <br />adjusted for slope and soil characteristics. The Revised Universal Soil Loss Equation <br />("RUBLE") may be used to calculate proper spacing for slopes based on site-specific <br />conditions. Factors taken icrto consideration include rainfall, soil erodibility, and steepness <br />of slope. On very steep slopes (i.e., greater than 2h:ly) terracing may be impracticable <br />because of the amount of material that must be moved and the relatively short distance <br />between structures. Terraces make good permanent secondary drainage features for <br />reclaimed areas. <br /> <br />C-3 <br />