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<br />Pile - An enlongated member, usually made of timber, concrete, or <br />steel, that serves as a structural component of a river-training <br />structure. <br /> <br />Piping - Removal of soi I material through subsurface flow of seepage <br />water that develops channels or "pipes" within the soi I bank. <br /> <br />Point bar - The convex side of a bend that is bui It up due to sediment <br />deposition. <br /> <br />Quarry-run stone - Natural material used for streambank protection as <br />received from a quarry without regard to gradation requirements. <br /> <br />Rapid drawdown - Lowering the water against a bank more quickly than <br />the bank can drain, which can leave the bank in an unstable <br />condition. <br /> <br />Reach - A portion of a channel between any two points. <br /> <br />Refusal - Erosion-resistant material placed in a trench (excavated <br />landward) at the upstream end of revetment ot prevent flanking. <br /> <br />Reinforced-earth bulkhead - A retaining structure consisting of <br />vertical panels and attached to reinforcing elements embedded in <br />compacted backfi I I for supporting a natural or artificial <br />streambank (a specific type of retaining wal I). <br /> <br /> <br />Retaining wall - A vertical structure used to maintain an elevation <br />differential between the water surface and top bank whi Ie at the <br />same time preventing bank erosion and instabi I ity. <br /> <br />Retard - Structure placed paral lei to a streambank to prevent erosive <br />currents from attacking the bank. <br /> <br />Revetment - Cover of erosion-resistant material placed to protect a <br />streambank. <br /> <br />Riparian - Pertaining to anything connected with or adjacent to the <br />banks of a stream. <br /> <br />Riprap - See stone riprap <br /> <br />River training structure - Any configuration constructed in a stream <br />or placed on, adjacent to, or in the vicinity of a streambank <br />that is intended to deflect currents, induce sediment deposition, <br />induce scour, or in some other way alter the flow and sediment <br />regimes of the stream <br /> <br />Rock-and-wire mattress - A flat or cyl indrical wire cage or basket <br />fi I led with stone or other suitable material placed on a <br />streambank or fi Iter as protection against erosion. <br /> <br />( <br /> <br />79 <br />