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' • Practicrl Approac~for EtTecuve E & S Control - 85 <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 Associarion. <br />' Field Note: For the purpose of establishing the benefit of an erosion control <br />practice or material, concentration of sediment in the runo water is not <br />considered appropriate. This is because a practce or material may have <br />a high absorprion/adsorptive capability or may increase the percentage of water <br />' which infikrates the soil. The amoutu of runoff might be less, thus increasing <br />the percentage sedimetu concentration in the volume of runoff water. <br />' V Reduction in Water Velocity {% of Controp <br />' Some manufacturers provide information on the effectiveness of their materials <br /> to reduce overland water flow velocities relative to a baze soil control. Where <br /> this information is available, it can be used (cautiously) for comparative <br /> purposes. <br />' Other information has been generated by the National Highway Cooperative <br />Research Program on velocity reduction afforded by various surface covers <br /> ranging from gravel to vazious 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 K 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 aze more sensitive to varying soil textures. For <br />' example, soil sealants needs 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 are sometimes less effective on "tight soils" or those of high <br />clay content. These sails 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 aze less effected by the porosity of a soil. <br />1 Fi <br />' <br />" <br /> and relaring erosivity to soil <br />Soil Triangle <br />eld Note: BY referring to the <br /> texture, one can derermine the relative erosion potemial of cenain types of soil. <br /> <br /> O 1995 IECA <br /> <br />