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Note : The following values are to be entered by the user for each area <br />in the watershed. The 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 <br />the area of a user - selected closed polyline. The user also has the option <br />to enter the area in different units. <br />Slope, S ( %) : Can be entered by the user or the program calculates <br />the slope when the user selects an area from the screen. <br />Length (L) : Can be entered by the user. If the user selects an area from the screen, <br />the length is not calculated since the Gross Erosion is directly calculated. <br />Topographical Factor (Ls) : Will be calculated from Length (L) and the Slope (S), <br />only when these values are entered by the user directly, as against calculated <br />by the program from the screen. In the second case, the value of Ls is calculated <br />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 <br />for each area defined. If the user selects an area from screen, E is calculated <br />in each grid and the cumulative value is calculated. <br />E = R « K « Ls « C « P , where all the parameters are as defined above <br />Volume Calculations : <br />Required User Input <br />Sediment Delivery Ratio (DR) : Default = 0.37 <br />Time Period,T (years) : Time of analysis; typically the time of the storm event <br />Density of the sediment (D) : The post- deposit density of the sediment <br />Runoff (1) : Calculated from some other routine like Curve Number and Runoff <br />Total Erosion (E, tons /year) = Sum of (E « Area) for all the areas <br />Revised January 2010 (PR06) Attachment 2.05.3(3) -14 -6 <br />