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The combination of 30 percent canopy cover and 30 percent ground <br />• litter gives an effective ground cover of 60 percent. The 60 percent <br />ground cover could be considered to a worst case condition at the <br />refuse pile after two growing seasons. The percent ground cover will <br />improve with time. <br />The P value is 0.6 (Leopold, Dunne 78). The P value is for the terra- <br />ces being used. <br />Using these values in the USLE, the erosion from the refuse pile is <br />estimated to be A = (40) (.25) (15.3) (.4) (.6) = 36.7 tons/acre/year. <br />This is for the first year of growth, when the refuse pile is unvege- <br />tated and only a layer of mulch on the surface. <br />As vegetation is established, the erosion will be lowered. After the <br />third growing season, the permanent vegetation should be well <br />established. The permanent vegetation will provide approximately 30 <br />percent canopy cover. The canopy cover in addition to the ground <br />• litter will provide an effective ground cover of 60 percent. The per- <br />manent vegetation will lower the C value in the USLE to 0.04. Using <br />the new C value in the USLE and the other values remaining the same, <br />The soil loss becomes A = (40) (.25) (15.3) (0.04) (.6) = 3.7 <br />tons/acre/year. <br />• <br />Applying the USLE equation to the benches, the first year erosion is <br />3.2 tons/acre/year. The R, K, and C values remain the same, 40, .25, <br />and .4 respectively. The LS value drops to 0.8 because the benches <br />are only 20 feet long and on a 10 percent slope. No P value is used <br />because there are no terraces. After vegetation is established, the C <br />4-52 <br />