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<br />e <br /> <br />Vegetative Linings <br /> <br />s <br /> <br />The classic tests on vegetative linings were performed by <br />Palmer, Law, and Ree of the Soil Conservation Service (SCS) <br />and are summarized in the publication; Handbook of Channel <br />Design for Soilartd'Water'Conservation (5). For <br />compatibility with the methods of this circular, those <br />results, in terms of maximum permissible velocity, have been <br />converted to maximum permissible depth curves for selected <br />grasses. The hydraulic resistance curves for vegetation <br />from the SCS report have been incorporated into this circular <br />without revision. <br /> <br />i <br /> <br />Bermuda grass sod, with a grass length of 2-1/2 inches was <br />tested by MSU in their vertical sidewall channels (3). The <br />sod seemed to work as well as established grass when compared <br />with, the SCS test results (5). Thus, sodding provides the <br />immediate protection of an established vegetative lining, <br />provided the installation is properly performed and gaps do <br />not exist between sod strips. <br /> <br />Rock Riprap Linings <br /> <br />. <br /> <br />A design procedure for rock riprap channel linings was developed <br />by Anderson at the University of Minnesota as a part of a <br />National Cooperative Highway Research Program (NCHRP) study <br />under the sponsorship of the American Association of State <br />Highway and Transportation Officials (AASHTO) (6). Empirical <br />erosion prevention and hydraulic resistance information was <br />developed based on a survey of results in the literature and <br />that information was incorporated into a new design procedure for <br />triangular and trapezoidal channels. Verification of the method <br />was performed in rectangular laboratory channels and through <br />field observations of four installations discussed in the field <br />evaluation report on the above NCHRP study (7). All of the test <br />installations were performing adequately as of June 1973. The <br />design techniques of NCHRP Report 108 were modified slightly <br />herein to conform with the concept of maximum permissible depth <br />of flow, as used in this circular. Methods similar to those of <br />NCHRP Report 108 for design of riprap on side slopes and a <br />procedure for designing the granular filter blanket for riprap <br />linings are contained in this circular. Criteria for plastic <br />filter cloth design and a new procedure for design of channel <br />protection in bends are also included. <br /> <br />e <br /> <br />e <br /> <br />5 <br />