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<br />floods will affect the magnitude of the benefit and must be estimated <br /> <br /> <br />by the engineer. Consideration would, of course, be given to encroachment <br /> <br /> <br />of development into the floodway, flood depths and velocities, and the <br /> <br /> <br />steepness of the rising flood hydrograph. As in the case of a~l contro- <br /> <br /> <br />versial items (whether benefits or costs), the benefit-cost analysis can <br /> <br /> <br />be performed with and without the debatable benefit, so that the effect <br /> <br /> <br />on the alternative selection can be understood and considered. <br /> <br /> <br />Land value enhancement benefits, where applicable, can be estimated <br /> <br /> <br />by considering the increased value that land will have when removed from <br /> <br /> <br />the flood hazard area. A considerable literature exists on this question <br /> <br /> <br />in the economics journals. <br /> <br />Indirect Benefits <br />Indirect benefits include reduction of indirect damages such as: <br /> <br /> <br />lost business and services, the cost of alleviating hardship, safe- <br /> <br /> <br />guarding health, rerouting traffic and related phenomena. Description <br /> <br /> <br />of the above indirect benefits is very difficult and estimation of them <br /> <br /> <br />is usually made by taking percentages of direct damage reduction benefits. <br /> <br /> <br />Data for estimating benefits resulting from reduction of indirect damages <br /> <br /> <br />are not a available as for direct benefits. One set of estimates which <br /> <br /> <br />was used in one study by the Corps of Engineers is as follows: [3] <br /> <br /> <br />1. Residential - 15% <br /> <br /> <br />2. Commercial - 35% <br /> <br /> <br />3. Industrial - 45% <br /> <br />4. Utilities - 10% <br />5. Public facil i ties - 34% <br />6. Agriculture - 10% <br />7. Highways - 25% <br />8. Railroads - 23% <br /> 43 <br />