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Appendix L: Critical Erosive Velocities for Grass and Soil <br /> Velocity <br /> Maximum permissible velocities of flow in vegetated channels absent of permanent turf reinforcement matting <br /> shall not exceed the values shown in the following table: <br /> Table L.1 Permissible Velocities for Channels Lined with Vegetation <br /> • <br /> Channel Slope lining Permissible <br /> Velocity'(ft/see) <br /> 0-5% Reed cant uygrass 5 <br /> Tall fescue <br /> Kentucky bluegrass <br /> 4 <br /> Grass-legume mixture <br /> Red fescue <br /> Redtop 2.5 <br /> Scrices lespedeza <br /> Annual lespedeza <br /> Small grains <br /> 5-10% Reed canarygrass <br /> Tall fescue4 <br /> Kentucky bluegrass <br /> Grass-legume mixture <br /> • <br /> Greater than Reed canarygrass <br /> Tall fescue 3 <br /> 10% Kentucky bluegrass <br /> Source:Anil and Water Conservation Engineering, Schwab,et at <br /> For vegetated earth channels having permanent turf reinforcement matting,the permissible flow velocity shall <br /> not exceed h ft/sec. Turf re:nfbrcemcnt matting shall be a machine produced mat of nondegradable fibers or <br /> elements having a uniform thickness and distribution of weave throughout. Matting shall be installed per <br /> manufacturer's recommendations with appropriate fasteners as required_ Examples of acceptable products <br /> include but are not limited to; <br /> • North American Green "C350"or"P300" <br /> • Greenstreak"PEC-MAT" <br /> • Tensar"Erosion Mat" <br /> 1 For highly erodible soils, permissible velocities should be decreased 25%. An erodibility factor(K) <br /> greater than 035 would indicate a highly erodible soil. Erodibility factors(K-factors)can be obtained <br /> from local MRCS offices. <br /> p <br /> L-1 ,1 <br />