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<br />Flow Deflection TlIChnlqu. . <br /> <br />e <br /> <br />must be properly keyed into the banks to prevent flanking. Live cribwalls must be built <br />during the dormant season, and some care must be exercised in cutting and handling the <br />brush used in the structures. <br /> <br />Cribs - Used on smaller streams on a limited basis, cribs, or log cribs, deflect erosive <br />cwrents away from the bank and induce sediment deposits bebind the structure. Cribs <br />are constructed during low flow in the shape of a 30-60-90 triangle. The long side of the <br />triangle should be towards the bank while the short end should be facing downstream so <br />the deflected flow win towards the center of the channel. Logs used in the construction <br />should be a minimum of 6 inches in diameter and the stone should be angular in shape <br />and keyed into the bank 12-24 inches. The crib height should be small enough to allow <br />flood waters to pass over the top. <br /> <br />Crib deflectors, shown in Figure 4 - 13, deepen channels, create meanders, remove sill, <br />and enhance aquatic habitat, but may cause bank erosion on the opposite side of the crib <br />if not properly constructed Cribs are economical if materials are located nearby and <br />unskilled labor is used. Cribs exposed above the water may be aesthetically displeasing <br />and the logs will need replacement due to rolling. <br /> <br />Costs for crib deflectors are typically about $200 each for construction and $30 for <br />annual maintenance. <br /> <br />FIGURE 4-13 <br /> <br />Crib Deflector <br /> <br />I <br />~ <br />4' Typical <br /> <br />Varies <br /> <br /> <br />Logs <br /> <br />Existing <br />Banldine <br /> <br />6' <br /> <br />~ <br /> <br />Flow <br /> <br />HighBankIine <br />/ <br />~Logs <br />~neToe <br /> <br />Existing <br />anldine <br /> <br />Logs <br /> <br /> <br />3-4.1 <br />~ <br /> <br />e <br /> <br />Colorado Erosion Control Manual <br /> <br />41 <br />