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<br />Methods I'or Controlling Erosion <br /> <br />e <br /> <br />Vegetation is an important variable in channel systems. Often it is bank vegetation that <br />resists ermion. Vegetation tends to stabilize interchannel bars and islands which may <br />subsequently alter flow lines and channel movement. <br /> <br />The intem,lated nature of these variables is such that, unlike rigid boundary hydraulics, <br />it is not possible to isolate and study the role of an individual variable. Quantitative <br />prediction of response can only be made if all of the required data are known with <br />sufficient accuracy. A complete understanding of all the physical processes that <br />influence lilY alluvial river is a complicated and time consuming effort. However, <br />certain geoeral relationships can be used to help detennine qualitative response to <br />changes imposed upon the channel or basin. <br /> <br />The foUo ..ing general relationships have been developed from previous studies <br />(Simons e:. al. 1976). and are very useful for qualitative prediction of channel response <br />to natural ,)r imposed changes in a river system: <br /> <br />(I) Depth of flow is directly proportional to water discharge. <br /> <br />(2) Channel width is directly proportional to both water discharge and sediment <br />discharge. <br /> <br />(3) Chann:l shape, expressed as width to depth ratio is directly proportional to sediment <br />discharge. <br /> <br />(4) Chann~1 slope is inversely proportional to water discharge and directly proportional <br />to both se,liment discharge and grain size. <br /> <br />(5) Sinumity is directly proportional to valley slope and inversely proportional to <br />sediment llischarge. <br /> <br />(6) TransllOrt of bed material is directly related to stream power and concentration of <br />fine material, and inversely related to the fall diameter of bed material. <br /> <br />When coupled with engineering knowledge and a morphologic understanding of the <br />river sysb:m, these relationships provide a powerful tool for assessing the impact of <br />proposed (lI"Ojects. <br /> <br />4.3 Methods of Classification. <br /> <br />In choosing a stream bank erosion control structure, the most important task is to <br />identify tlle causes of erosion. Causes of erosion can be broken down into three general <br />types: hydraulic. geotechnical. or a combination of both. These types have been <br />discussed earlier in chapter 3. <br /> <br />Bank stahilization sttUCtures can be grouped into three broad categories based upon <br />function: <br /> <br />e <br /> <br />26 <br /> <br />Colorado Erosion Control Manual <br />