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Prrctical Approaches for Effective E & S Control - SS <br />reduce sediment delivery can be constructed by referring to available literature <br />• from the manufacturers and through the proceedings of the International Erosion <br />Control Association. <br />Field Note: For the purpose of establishing the betteftt of an erosion control <br />practice or material, concentration of sediment in the runoff water rs not <br />considered appropriate. This is btcause a practice or materiel may have <br />a high absorption/adsorptive capability or may increase the percentage of water <br />which infiltrates the soil. The amount of rrutoff might be less, thus increasing <br />the percentage sediment concentration in the volume of runoff water. <br />V Reduction in Water Velocity (% of Control) <br />Some manufacturers provide information on the effectiveness of their materials <br />to reduce overland water flow velocities relative to a bare soil control. Where <br />this information is available, it can be used (cautiously) for comparative <br />P~~s• <br />Other information has bete generated by the National Highway Cooperative <br />Research Program on velocity reduction afforded by various surface covers <br />ranging from gravel to various types of vegetation. Manning's "n" or <br />roughness coefficients can also be used for comparison of dissimilaz practices or <br />materials. <br />K Soil Texture Sensitivity <br />Like all other factors under consideration in this ECBM, soil texture sensitivity <br />is a qualitative measurement; however, a relationship can be drawn between our <br />"K" and the if factor in the USLE. Our "K" factor relates to the varying <br />percentages of sand, silt and clay in a soil. <br />Some practices and materials are more sensitive to varying soil textures. For <br />example, soil sealants nerds to penetrate the soil in order to be effective. The <br />sealants act by filling voids and interstitial areas between soil particles. In this <br />regazd, sealanu aze sometimes less effective on "tight soils" or those of high <br />clay content. These soils resist penetration and have low void space. <br />Adjustments must be made to the dilution ratio of the sealant mixture or another <br />technology selected. In contrast, dry surface treatments, such as blown straw, <br />wood fiber mulch, erosion control blankets, etc. which don't require subsurface <br />penetration are less effected by the porosity of a soil. <br />Field Note: BY referring to the "Soil Triangle' and relating erosivity to soil <br />texture, one can derennine the relarive erosion potential of cenain types of soil. <br />O 1995 IECA <br />