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<br />III. UNDERSTANDING STREAM BANK EROSION <br /> <br />The control of the Interrelated forces causing streambank 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 rivers, engineers cannot consistently predict 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 al I but the largest projects. However, ful I scale experimentation and testing on <br />the stream Itself is another form of modeling 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 more workable solutions to an erosion problem. <br />But costs generally preclude t~e use of the "bestlt solution, and the use of alternate and <br />Inferior solutions wi II 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 failed. 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 Ieate 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 />Summarized below are some important facts an Individual property owner should know before <br />beginning a bank erosion control project: <br /> <br />. <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 I I Y <br /> <br />require <br /> <br />substantial <br /> <br />structures <br /> <br />. <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 />frequen11y not sufficient to arrest the bank erosion. <br /> <br />on bank erosion control <br />These efforts are quite <br /> <br />. <br /> <br />Future environmental studies may dictate that certain structures will not be <br />approved for construction and/or maintenance. <br /> <br />5 <br />