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<br />Methods I"or Controlling Erosion <br /> <br />e <br /> <br />Live Crib walls - Live cribwalls are constructed of logs or timbers cross-stacked to <br />provide g ilps through which willows, dogwood, or other brush can be placed and <br />protrude. 'lbese branches take root and grow. The crib structure is filled with alternating <br />layers of soil and brush. Over a period of time the timbers decay, but the brush will have <br />grown suUciently to produce a reinforced root structure capable of resisting the erosive <br />force of cIJrrents. Live cribwalls, shown in Figure 4 - 12, are appropriate structures for <br />protecting limited sections of bank that are composed of highly erodible material or that <br />are subj..:t to local scour by secondary cwrents. Cribwalls often extend slightly <br />riverward of the bank, and they have impacts similar to those for hardpoints. <br /> <br />Usually a'ter one growing season live cribwalls have the appearance of a naturally <br />vegetated bank, and the visual benefits are superior to most other structures that could <br />be used in similar situations. The brush incorporated into cribwalls can provide <br />improved riparian habitat and some aquatic benefits resulting from shade and organic <br />debris. Li ve cribwalls have been used throughout the U.S. and Canada on streams <br />ranging in size up to that of the Tennessee- Tombigbee Waterway. It is a useful system to <br />repair and further prevent scour holes. <br /> <br />FIGURE 4 -12 <br /> <br />Uve log crib <br /> <br />r--v,mes I <br />~ <br />4' Typical Logs <br /> <br /> <br />Existing <br />Banldine <br /> <br />6' <br /> <br />.----J Flow <br /> <br />Logs <br /> <br /> <br />Existing <br />BanIdine <br /> <br /> <br />Log <br /> <br />~ <br />3~ <br /> <br />-=:::::::r--FIow <br /> <br />Stone Toe <br /> <br />Live cribwalls have performed well. even where some other vegetative treatments have _ <br />been unsuccessfuL A good foundation is important to cribwall success, and the structure . <br /> <br />40 <br /> <br />Colorad.) Erosion Control Manual <br />