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<br />Freeboard is a safety factor to account for unknowns such as wave action, <br /> <br />Levees are generally credited for preventing one half the damages in the <br /> <br />freeboard range, <br /> <br />2) The protection offered by any structure is dependent on its <br /> <br />structural integrity, A project can only be considered effective insofar <br /> <br />as it has structural integrity, <br /> <br />An existing levee cannot be considered as offering any protection at <br /> <br />elevations above which inadequate structural quality would cause it to <br /> <br />fail, Likewise, as discussed in Chapter VIII, there can be no benefits <br /> <br />claimed for flood damage reduction attributable to replacement or <br /> <br />rehabilitation of such structures unless it can be shown they are <br /> <br />structurally deficient, Channels and interior drainage ditches should be <br /> <br />sufficiently maintained so that sediment, logjams, and debris are not <br /> <br />likely to cause a significant reduction of capacity..:., Structural <br /> <br />investigations should indicate if levees are free of uneven settlement, <br /> <br />inadequate seepage control, or deteriorated construction material, <br /> <br />STEP TWO: SELECT PLANNING REACHES <br /> <br />Definition. The reach is the primary unit of plan formulation. The <br /> <br />river length and affected tributaries are divided into "reaches" <br /> <br />throughout which the relation between discharge and stage remains <br /> <br />practically constant, and into zones where development or use changes <br /> <br />appreciably with stage, Frequency, flow, stage and damage data are used <br /> <br /> <br />for each reach; thus data must be representative of the actual frequency <br /> <br />V-6 <br />