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<br />Methods I'or Controlling Erosion <br /> <br />e <br /> <br />4.8 Summa ry - <br /> <br />In any alII ivial channel there is a set of complex relationships that intertwine a number <br />of importmt physical parameters. Water discharge is perhaps the most important <br />variable, tut sediment transport, energy slope, geology, soils, vegetation, and channel <br />geometry are also major physical processes. Changes to anyone variable, whether <br />induced b~' nature or as a result of man's activities, causes changes in all other variables. <br />Because of the interrelated nature of these variables, it is difficult to perform either a <br />quantitati\ e or qualitative analysis without looking at the system as a whole. <br /> <br />Bank proIl:ction structures affect the hydraulics, sediment transport, and geometry of the <br />adjacent channel. Stabilization structures can be grouped into three categories based <br />upon function. These groups include armoring structures, deflective structures, and <br />erosion capacity reduction structures. The local impacts from bank protection structures <br />vary by function, materials, design, and construction methods. <br /> <br />Streambar Ie protection projects can result in a wide range of positive and adverse <br />envjn)nmmtal impacts. Through proper planning and design, negative impacts can be <br />minimizecl and positive impacts maximized. This requires a thorough understanding of <br />the river slstem and adherence to several design parameters. <br /> <br />Cumulati\e impacts are much more difficult to assess than local impacts. It can be <br />assumed that by minimizing loca1 impacts cumulative impacts are also minimized. <br />Structures that have little local impact include revetments, parallel fences, and certain <br />revegetati'ln techniques. Structures such as hardpoints, retards, and short fence dik:es <br />have mOle local impact than the aforementioned structures. A more thorough <br />examinati,)n of these structure types will1ikely indicate that, within certain limitations, <br />they willllllve no significant cumulative impact. Methods such as selective clearing and <br />snagging, large jetties. and chute closures can have substantial local and cumulative <br />impact. It is imperative that all structures utilize suitable materials, have proper design, <br />and that a strict maintenance procedure be adhered 10. <br /> <br />e <br /> <br />52 <br /> <br />Colorado ErosIOn Control Manual <br />