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<br />Jetty Stream Bank Erosion Control <br /> <br />Jetties are an effective method of controlling stream bank erosion on slight <br />to moderately meandering curves. Jetties typically are not fea.ible on sharp <br />curves. Jetties function by deflecting the flow from the stream allay from the <br />stream bank. Jetties can be constructed completely from rock or they can have <br />a dirt, .and or gravel core with rock on the surface for erosion protection. <br />Rock must be large enough to withstand the force of the water without being <br />displaced. The size and spacing of the jetties depends on the physical char- <br />acteristic. of the stream; for example, the channel width and the sharpness of <br />the curve. A jetty should not extend into the stream from the bank more than <br />20 percent of the channel width. The design of jetties requires an evaluation <br />of the downstreem channel and bank conditions to avoid causing erosion and <br />other problem.. <br /> <br />Je ttie. <br />tices. <br />reaches <br /> <br />can be u.ed to protect a stream bank without u.ing any other prac- <br />However, it i. generally recommended to .hape and seed the bank <br />between jetties. <br /> <br />Maintenance requirement. for this practice include replacing or repo.itioning <br />any rock which has been displaced. Over a period of a few year., sediment <br />bar. may develop near the down.tream end of the jetty. These gravel bars <br />should be removed to keep the jetty system functioning properly. A mainten- <br />ance inspection .hould include a look at the down.tream bank to check for <br />ero.ion which could have been cau.ed a. a result of the jetties. <br /> <br />46 <br />