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<br />EXHIBIT 3 <br />EXAMPLE COMPUTATION <br />EXPECTED ANNUAL FLOOD DAMAGE COMPUTATION <br />COMPUTER PROGRAM 761-X6-L7580 <br /> <br />INTRODUCTION <br /> <br />This example is intended to illustrate the computational methods <br />used in computer program, Expected Annual Flood Damage Computation, <br />to compute single event damage, expected annual damage and equivalent <br />annual damage. It is assumed that damage, flow, stage and frequency <br />data have been collected by field surveyor other means, and that <br />these data have been put into the traditional stage or flow-damage, <br />stage-flow and stage or flow-frequency relationship form. Stage- <br />damage, stage-flow and flow-frequency relationships were selected for <br />this example and are shown on Figures 1, 2 and 3. In addition to <br />these, the computer program can handle other combinations such as <br />frequency-damage; or stage-damage and stage-frequency; or flow-damage <br />and flow frequency; or flow-damage, stage-flow and .stage-frequency. <br />The computational procedures are essentially the same for all combina- <br />tions. <br /> <br />DAMAGE-FREQUENCY RELATIONSHIP <br /> <br />When Figures 1, 2 and 3 are combined, the damage-frequency relation- <br />ship shown in Figure 4 is obtained. There are several ways to do this <br />by hand. One might select elevations on the stage-damage curve (Figure 1), <br />use these same elevations to find corresponding flows on Figure 2, use <br />the flows to find corresponding frequencies on Figure 3, and thus <br />rel ate damage to frequency. Or, one mi ght reverse the procedure and <br />begin with selected frequencies and find corresponding damage. What is <br />of critical importance to achieve an acceptable level of accuracy in <br />constructing the damage-frequency relationship is that each relationship <br />used in the"derivation be defined with the right points such that a <br />linear interpolation between points is a reasonable representation of <br />the actual relationship. In hand computations this is sometimes <br />difficult to do unless a large number of points are selected. For <br />example, while sufficient elevation points may be selected to define a <br />stage-damage relationship, these same elevations may not accurately <br />define the stage-flow relationship. Since hand computations use one <br />set of discrete points the only alternative is to go back to the stage- <br />damage relationship and take additional points. In the computer program <br />each relationship used in the derivation of the damage-frequency function <br /> <br />EXHIBIT 3 <br />1 of 12 <br />