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<br />) <br /> <br />) <br /> <br />Expected values computed for frequencies in Step Eight are weighted <br /> <br /> <br />by their exceedance probability. In most floodplain areas, the high <br /> <br /> <br />frequency events usually account for the major share of the average annual <br /> <br /> <br />flood damages. Damages for specific floods not computed in the damage <br /> <br /> <br />frequency relationship are interpolated to create the function for <br /> <br /> <br />expected annual damages. <br /> <br />Derivation-general: This is the method most frequently used by the <br /> <br />Corps to compute expected annual damages. As will be seen later, it <br /> <br />involves the combining of three basic functions: stage-damage, stage- <br /> <br />discharge and discharge-frequency, to define a fourth function, the <br /> <br />damage-frequency relationship. It has already been established how these <br /> <br />functions are developed. Suffice it to say that the stage-damage curve, <br /> <br />which relates dollar damage to each stage of flooding, is usually the <br />responsibility of the economist and/or planner while ~evelopment of the <br />other two curves is usually the responsibility of the hydraulic and <br />hydrologic engineer. This is not to imply that responsibilities should be <br />performed independently of each other. On the contrary, as explained in <br /> <br />earlier sections, team effort is necessary to insure internal consistency <br /> <br />and consideration of all relevant economic and hydrologic factors. <br /> <br />Figure V-8 shows the relationships discussed above and the schematic <br /> <br />for deriving expected annual damages. Stage-damage Curve A is combined <br /> <br /> <br />with stage-discharge Curve B to generate damage-discharge Curve D by <br /> <br /> <br />picking a damage point and relating it to a stage on Curve A, identifying <br /> <br /> <br />the same stage and relating it to a discharge estimate on Curve B, and, <br />finally, using the estimates identified for discharge and damages as a <br /> <br />point on Curve D. This process is repeated until Curve D is traced out. <br /> <br />) V-49 <br />