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7.3 Hydrologic and Hydraulic Evaluations <br />This substask encompasses a complete hydrologic analysis, determining the <br />design flood and the sizing of the spillway to handle the design flood. MKE <br />shall perform flood hydrology computations to determine the PMF and 50 percent <br />PMF hydrographs, based on HMR No. 55. <br />For Barnes Meadow Dam, MKE shall make a computation of a theoretical breach <br />and the resulting flood hydrograph, along with an estimate of flood channel <br />levels for unattenuated flows downstream. This will provide an indication if <br />there is potential for obtaining approval from the State Engineer of using a <br />design flood smaller than the PMF based on the principles of the "no <br />incremental damage approach ". <br />The PMF and 50 percent PMF shall be routed through the existing reservoir and <br />spillways to determine the degree of safety or the amount of overtopping that <br />would theoretically occur. T. low hydrographs shall also be used in <br />conjunction with a variet,, s ay dification alternatives to determine <br />what changes in capacity e Muir = o 'ly pass the selected design flood <br />flow at the Barnes Meadow site <br />The flood routing study ' ;shall require the selection of spillway hydraulic <br />characteristics, storage capacity data, and discharge rating curves. At the <br />same time, structural elements shall be evaluated. Obtaining possible <br />additional flood handling capacity may be accomplished by a combination of <br />spillway modifications and minor raising of the dam crest. Roller compacted <br />concrete shall be considered for providing needed erosion protection to the <br />spillways. <br />Based on spillway flows, as determined by the hydrologic evaluation above, the <br />adequacy of the existing spillway structures to withstand the erosive effects <br />of the calculated spillway flows shall be determined. The extent of spillway <br />modifications and additional erosion protection required to safely pass the <br />calculated spillway flows shall be determined for each spillway structure. <br />- 11 - <br />