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• Universal Soil Loss Equation :Use in Survcadd Program <br />-------------------------------------------------------------- <br />-------------------------------------------------------------- <br />Required User Input <br />------------------- <br />------------------- <br />Note :The following values are to be entered by the user for each area in the watershed. The <br />method for obtaining these parameters is left to the user. <br />Rainfall Factor (R) :Default = 50; <br />Erodability Factor (K) :Default = 0.37 <br />C Factor (C) :Default = 0.5 <br />P Factor (P) :Default = 1.0 <br />Geometric Information <br />Area (sq units) :Can be entered by the user or the program calculates the area of auser-selected <br />closed polyline. The user also has the option to enter the area indifferent units. <br />Slope, S (%) :Can be entered by the user or the program calculates the slope when the user <br />selects an area from the screen. <br />Length (L) :Can be entered by the user. If the user selects an area from the screen, the length is <br />not calculated since the Gross Erosion is directly calculated. <br />Topographical Factor (Ls) :Will be calculated from Length (L)and the Slope (S), only when these <br />values are entered by the user directly, as against calculatedby the program from the screen. In <br />the second case, the value of Ls is calculated for individual grids and not for the entire area. <br />Ls = (L/72.6)^m * ((430*S^2 + 30*S + 0.43)/(6.613)) <br />where L and S are defined above and <br />m = 0.5 if S=>5%; = 0.3 if S<= 3% ; = 0.4 otherwise. <br />Gross Erosion, E (tons/acre/year) :Calculated from the above defined parameters for each area <br />defined. If the user selects an area from screen, E is calculated in each grid and the cumulative <br />value is calculated. <br />• <br />(Revised 12/01) Attachment 2.05.3(3) -10-6 <br />