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<br />III. UNDERSTANDING STREAMBANK EROSION <br /> <br />The control of the interrelated forces causing stream bank erosion is very difficult. Over <br />the last century, many of the great rivers In this country have been studied in an attempt <br />to develop them for navIgation, power, water supply, and irrigation. But even wIth this <br />concentrated study of r j vers, ang I neers cannot cons I stant Iy pred let the behavIor of a <br />river at any given location from a cursory examination. To reliably determIne the <br />specific behavior of a given river reach, It would be necessary to conduct expensive <br />physical model tests. The expense Involved in these kinds of tests usually preclude their <br />use In all but the largest projects. However, full scale experimentation and testing on <br />the stream itself is another form of roodeling which can be very effective, and this "trial <br />and error" approach is often used to solve bank erosion problems. An experienced engineer <br />can often diagnose and prescrIbe one or roore workable solutions to an erosion problem. <br />But costs generally preclude t~e use of the "best" solution, and the use of alternate and <br />Inferior solutions will reduce the chances of success. However, there are cases where <br />minimal erosion control measures have succeeded but there are also cases where substantial <br />erosion control measures have fal led. An individual embarking on a bank erosion control <br />project should be aware of the risks Involved, and that even with the best advice, factors <br />and conditions may exist and be overlooked or be created by the construction works which <br />could result In an unsuccessful project. <br /> <br />In attempting to control or modify the nature of a river the environment must be <br />considered. Unfortunately, environmenTal studies have been quite limited regarding the <br />possible Impacts of streambank erosion conTrol measures on the aquatic and terrestrial <br />ecosystems of streams. Future stud i es may I nd i cate that certa I n structura I measures may <br />be detrimental to the stream environment. If such studies so indicate, it may mean that <br />certain structures wi I I no longer be approved for construction and/or maintenance. <br /> <br />Summarfzed below are some Important facts an Individual property owner should know before <br />beginning a bank erosion control project: <br /> <br />* The river forces contribUTing to bank erosion and natural meandering of rivers are <br />powerful and persistent forces that are difficult to deter. <br /> <br />. <br /> <br />Positive <br />InvolvIng <br /> <br />control of <br />significant <br /> <br />these forces <br />Investment. <br /> <br />genera II Y <br /> <br />requ I re <br /> <br />substantial <br /> <br />structures <br /> <br />* Other than expensive model testing, the most effective remedial measures can best <br />be determined by the judgment of an engineer who has had experIence with bank <br />erosion problems. <br /> <br />. <br /> <br />Because Individuals generally have limited funds to spend <br />projects, they ar~ forced to construct minimal projects. <br />frequently not sufficient to arrest the bank erosion. <br /> <br />on bank erosIon control <br />These efforts are quite <br /> <br />* Future environmental studies may dictate that certain structures will not be <br />approved for construction and/or maintenance. <br /> <br />5 <br />