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' DESiG\ OF CHASxELS FOR CSIFORM FLOW 1HS <br />establishment, the grass will grout and the channel will be stabilized under <br />ondition of low degree of retardance. The channel µ•i11 not reach its <br />~ximum capacity until the grass cover is fully developed and well <br />established. Therefore, it is suggested that the hydraulic design of a <br />o assed channel consist of two stages. The first stage (A) is to design <br />~e channel for stabilit}•, that is, to determine the channel dimensions <br />der the condition of a lower degree of retardance. The second stage <br />TAa LE ~-G. PEa11la51a LE ~ELOCITIEa FOR CHn S]ELS LIxED wlTH Ganss~ <br />Permissible velocin~, fps <br />Cover Slope range, <br />% ErOSIOn-resistant Easily eroded <br />soils soils <br />Bermuda grass <br />1 <br />BuRalo grass, ICentuckr bluegras?, <br />~ smooth brnmr, blue grams <br />Grass mixture <br />0-5 8 8 <br />5-10 i 5 <br />>10 ~ 6 + <br />0-5 7 ' S <br />5-10 ~ 6 + <br />>10 i 5 , 3 <br />0-5 5 + <br />5-10 + ~ 3 <br />Do not use nn slopes steeper than 10 0 <br />Lespedeza serirea, keeping love' 0-5 '. 3.5 'i ? 5 <br />grass, isehaemum (yellow blur, Do not use on slopes steeper than 5%, except for <br />stem), kudzu, alfalfa, crabgrass ~ side slopes in a combination channel <br />Annuals-used on mild slopes or as 0-~ ~ 3. ~ ' '_' S <br />' temporary protection until per- ~ lise on slopes steeper than 5 c is not recom- <br />manent covers are established, mended <br />common lespedeza, Sudan grass <br />REUnaes. The values apply to average, uniform stands of each type of cover. <br />' line velocities exceeding 5 fps only where goad covers sad proper maintenance can be <br />obtained. <br />• [i.S. Soil Conservation Service [411. <br />(B) is to review the design for maximum capacity, that is, to determine <br />the increase in depth of flow necessary to maintain a maximum capacity <br />under the condition of a higher degree of retardance. For instance, if <br />common lespedeza is selected as the grass for lining, the common lespedeza <br />' of 1oµ- vegetal retardance (green, average length 4.$ in.) is used for the <br />first stage in design. Then, in the second stage, the common lespedeza <br />of moderate vegetal retardance (green, uncut, average length 11 in.) <br />' should be used. Finally, a proper freeboard is added to the computed <br />