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<br />the fan. Below the end of the channel, flow <br />braiding and flood path instability recur. <br />Abrupt changes in channel shape. capacity or <br />direction cause, as shown in the model tests, <br />local scour or deposition and failure of the <br />channel. Such changes should be avoided. <br />Channels are most effective when used in <br />combination with debris basins or detention <br />dams. <br /> <br />Public Acceptance <br />General perception of reliability and good <br />protection, despite poor past performance. <br />Viewed as unsightly and disruptive to <br />community. <br />Safety hazard for children. <br />Costs are high. and are typically paid <br />federal and state agencies. <br /> <br />by <br /> <br />Required Maintenance <br />Sediment removal and channel <br />flood. <br />Routine inspection and maintenance of levees. <br /> <br />repair after each <br /> <br />.!l.J:..Q..e. structures <br /> <br />Susceptibility <br />Drop structures. because they are designed to <br />dissipate large amounts of energy in a small <br />area, are subject to severe erosion and <br />potential undermining. The foundation and <br />structure must be robust to prevent failure. <br /> <br />Effectiveness <br />Substantially reduce scour on steep slopes and <br /> <br />79 <br />