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guidelines recommended below for structural BMP's also apply here. An <br /> effort should be made to maximize the drainage areas of structural BMP's <br /> and to rely upon a regional approach where feasible. '* <br /> 8.4.2 BUFFER ZONES <br /> Although not a panacea for nonpoint pollution management, buffer zones <br /> along streams and reservoirs should be included in the overall watershed 4' <br /> management plan package. By preventing development from encroaching upon <br /> streams, buffer zones can help minimize stream channel erosion downstream <br /> of urban development. If properly situated and kept in an undisturbed <br /> natural vegetation, buffer zones which receive sheetflow runoff (i.e. , , .. <br /> runoff which flows slowly in a "spread out" type of pattern, rather than <br /> being concentrated in a swale) from adjoining urban areas can achieve some <br /> reductions in nonpoint pollution discharges. Effective use of buffer zones <br /> can increase the overall factor of safety associated with the watershed <br /> management plan. <br /> Width (i.e. , distance from the stream to -the edge of the buffer) is -the <br /> critical factor in determining the effectiveness of a buffer zone. <br /> Recommended parameters that should be considered to determine buffer zone <br /> width include: <br /> o Amount and velocity of runoff draining through the buffer _ <br /> zone which is determined by: <br /> Land use and treatment above buffer zone <br /> Slope above buffer zone _ _ <br /> Length of slope above buffer zone <br /> Soil erodibility above buffer zone <br /> o Physical properties of the buffer zone, including: <br /> Type of vegetation within-the-buffer-zone <br /> - Slopes within the buffer zone <br /> 8-5 <br />