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U N- 2 0- 8 9 T U E 2 1 1 4 E U A N S ~ <br />• <br />Eatlmating Soll Losses from Water Eroslpn <br />The Universal Soil-Loss equation can be used rte a <br />planning tool for estimating roil lose end evaluating <br />alternative fund treatment measure9. The procedure <br />has been used Por many years by the Soil Conservation <br />5ervicein dtvcloping conservation plans on farmland. <br />Recent developments hove expanded its use as a means <br />of estimating soil loss on various types of protect areas. <br />THB UNIVERSAL SOIL•1.055 EQUATION <br />(Modified for project sites) <br />A=K(or~l)xKxLSxC <br />A -The computed loll loss expressed as tans per sere <br />per year. <br />A -The average annual erosion index for a apecltlc <br />geographic region, conslderlttg amount, time and <br />duration or the rainfall. <br />B R I G G S <br />ATTORNEYS P 0 6 <br />• <br />EI -The erosion index fur only s portion of the year, <br />Derermine the percentage of the total erusipn <br />index and multiply tinter the total annual '•R" <br />factor shown on Figure 7. See Figure li to deter- <br />mine the percent of E.I. <br />K -Tho roil erodiblllty factor based on particle size <br />distribution, organic matter content, su•ucwtt <br />and permeability. Contact the Soil Conservation <br />Service forfaetor values. <br />LS-The !actor that accounts for the length and per• <br />cent slope, Ste Figure 9. <br />C - Tht soil cover factor. This factor accounts for the <br />soli protection provided by various kinds, and <br />amounts of soil Cover. See rlgure 10 or 11. <br />Example 5ltuatton: <br />An urban development project Is planned in Arapahoo <br />County. 1'o prtdiet annual soil lose, determine the ap• <br />plicable A, K, LS, and C Factors. The product of these <br />factors Is nn estim;tte of tuns of soil loss per acre per <br />year. It may be necessary to divide the area into seg• <br />manta to account tar variation In factor values, !n this <br />example, notice the "C" tttctor is 1.0, which indicates <br />that rite soil will be essentially void of protective cover. <br /> <br />5egmenl 1 5D x .32 x 4,0 x 1,0 64 tons x 4 Ae ~ 256,0 tons <br />H K LS C <br />Segment 2 SO x .2g x I.4 x 1.0 ^ 19.6 tons x 6 Ac - 1 i7 6 tone <br />Total Tons/Yr 313.6 tonx <br />To predict soil loss for a portion of the year, factot•"R" <br />will need to be ad}usted by the percentage of the erosion <br />index occurring during that portion of the year. hog <br />example to determine the E.I. for August, September <br />and Oewber, refer to Figure 8. Multiply the pereentaya <br />Prom Figure 8 times the "R" value for that geographical <br />re¢ion, The result is the 8.1. for that period of the year, <br />Therefore, an "R" facwr of 50 would bt adJustnd to <br />13.5 (SO x 27'/n). <br />Segment 1 13.5 x 32 x 4,0 x 1.0 ^ 17.2 x 4 Ae = 68.8 <br />F.,l, K LS C <br />Segment z 13.s x .2ti x l.a x 1.0 5.2 x 6 Ac - 31,,z <br />Total runs during Aua-Oct 100,0 tons <br />~~•. 2ti <br />' ,a~, A^ , <br />'Y(! 1 <br />r mb <br />!'. <br />,'i,;i: <br />i.M .. <br />i.' ,~ <br />•IY r!el~ ,. <br />