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<br />Learn-Assess <br /> <br />Channel Alterations <br /> <br />Channel alterations increase the flow-carrying <br />capacity of a stream's channel and thereby reduce <br />the height of a flood. The various types of <br />alterations include straightening, deepening, or <br />widening the channel, removing debris, paving the <br />channel, raising or enlarging bridges and culverts, <br />and removing dams and other obstructions. <br /> <br />Channel alteration is widely practiced by state and <br />local governments to control flooding by rapidly <br />conveying storm runoff through populated locales <br />to downstream areas. The Corps and the Soil <br />Conservation Service also undertake channel <br />alterations. The Corps projects typically lie on <br />larger streams and rivers, while Soil Conservation <br />Service works mostly in smaller streams on the <br />upper portions of watersheds. The Soil <br />Conservation Service has provided assistance in <br />the construction of 10,700 miles of open channels. <br /> <br />The use of channel modifications has decreased <br />primarily because of the potentially adverse <br />environmental impacts. Alternative designs are <br />now developed that include less straightening of <br />channels, employ more gradual slopes, and use <br />natural vegetation or riprap rather than <br />concrete-lined channels. This minimizes <br />destruction of fish and wildlife habitat, helps <br />maintain water quality, and avoids undesirable <br />downstream impacts. <br /> <br />Home Learoin2 Center Back <br /> <br />High Flow Diversions <br /> <br />Diversions intercept flood waters upstream of a <br />damage-prone or constricted area and convey them <br />around it through an artificial channel or a <br />designated flow-way. Diversions may either <br />completely reroute a stream or collect and <br />transport only excessive or potentially damaging <br /> <br />Page IS of36 <br />