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<br />to development within the floodplain. This will be affected by existing <br /> <br /> <br />regulations such as floodplain ordinances, community awareness of flooding <br /> <br /> <br />potential and consequences, and development pressures. The engineer must <br /> <br /> <br />estimate the probable encroachment which would result without the bene- <br /> <br /> <br />fit of the results of his flood control study. <br /> <br /> <br />It is also desirable to know how the present situation compares <br /> <br /> <br />with the future in terms of the flood magnitudes and resulting damages. <br /> <br /> <br />This will require the development of flood hydrology for the existing <br /> <br /> <br />situation. The same recurrence intervals should be used as for the <br /> <br /> <br />future hydrology. <br /> <br /> <br />Floodplains are delineated on topographic maps yielding estimates <br /> <br /> <br />of the depths, lateral limits and velocities of the flooding. Appropriate <br /> <br /> <br />hydraulic study techniques should be utilized. <br /> <br />Formulation of Alternatives <br /> <br />Once the magnitude of the flooding problem is defined, specific <br />alternative measures for solution are formulated to accommodate the <br />design flows. The engineer should be aware of the effect that each <br />alternative will have on the flood hydrology. The formulation of <br />alternative solutions is a creative process and requires the engineers <br />best efforts. It is not discussed in depth here, being beyond the <br />scope of this report. <br /> <br />Benefit-Cost Analysis <br /> <br /> <br />The following benefit-cost analysis is presented for use. The <br /> <br /> <br />procedure is presented in step-by-step fashion with an example given <br /> <br /> <br />to help explain the steps. <br /> <br />55 <br />