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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 feasible on sharp <br />curves, Jetties function by deflecting the flow from the streal. allay from the <br />stream bank. Jetties calL be constructed completely from rock 0:' they can have <br />a dirt, sand or gravel cc,re with rock on the surface for erosiOll protectLon. <br />Rock must be large enougb to withstand the force of the water wlthout being <br />displaced. The size and spacing of the jetties depends on the physical char- <br />acteristics of the streaa; 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 require:, an evaluation <br />of the downstream channel and bank conditions to avoid causing erosion and <br />other problems. <br /> <br />1 <br />~ <br /> <br />Jetties <br />tices. <br />reaches <br /> <br />can be used to protect a stream bank without using any other prac- <br />However, it is generally recommended to shape and seed the bank <br />between jetties. <br /> <br />Maintenance requirements for this practice include replacing or repositioning <br />any rock which has been displaced. Over a period of a few years, sediment <br />bars may develop near the downstream end of the jetty. These gravel bars <br />should be removed to keep the jetty system functioning properly. A mainten- <br />ance inspection should in:lude a look at the downstream bank to check for <br />erosion which could have been caused as a result of the jetties, <br /> <br />~' <br />1 <br />J <br />~ <br />1 <br /> <br />1 <br />J <br /> <br />J <br />~ <br /> <br />46 <br />