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<br />Where a later fl oodfl ow-frequency analysis provides <br />discharges that differ from those established previously in <br />studies on the same stream, the latest discharges shall be <br />adopted if the previously established discharge do not fall <br />within the 95 and 5 percent confidence limits (90 percent <br />confidence interval) of the most rc~ent _estimates. The <br />previously established discharges shall be adopted if they <br />fall within the 75 and 25 percent confidence limits (50 <br />percent confidence interval) of the most recent estimates. <br />Where the previously established discharges fall between 50 <br />and 90 percent confidence intervals of the most recent <br />estimates, the situation shall be presented to the Board <br />for resolution. <br /> <br />C. Hydraulic Analysis <br /> <br />1. Water Surface Profiles. Hydraulic calcula- tions shall <br />be performed to define, at a minimum, the water surface <br />profiles for the 10-, 50-, and IOO-year flood frequencies <br />as developed in the hydrologic analysis. The hydraulic <br />calculations for each frequency flood shall be summarized <br />in a frequency- elevation table or, in lieu of the table, <br />may be shown on the graph of water surface profiles. The <br />table shall include, at a minimum, the stream station for <br />each cross section, cross section identification, peak <br />discharges, and water surface elevations. The water <br />surface profiles shall show, at a minimum, the elevations <br />for the 10- and IOO-year flood. The Board recommends the <br />50- and SOD-year water surface profiles be shown in <br />addition to other profiles. <br /> <br />2. Floodolain Boundaries. Flooded area maps shall show, at <br />a minimum, the floodplain boundary of the IOO-year flood. <br />Where more than one floodplain may be delineated on the <br />maps, the Board recommends the SOD-year floodplain be shown <br />in addition to the IOO-year floodplain. The floodplain <br />boundaries shown on the flooded area maps shall be <br />consistent with the flood water surface profiles. <br /> <br />3. MethlJdoloqy. The hydraulic analysis for detailed <br />floodplain information shall be based on the following <br />methods, or any other method approv€d by the Board, as <br />appropriate: <br /> <br />-12- <br />