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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Hydraulic Analysis <br /> <br />Analyses of the hydraulic characteristics of the White River and Sulphur <br /> <br />Creek with-in the study area were carried out to provide estimates of the water <br /> <br />surface elevations of floods of the selected recurrence intervals along each stream. <br /> <br />The water surface elevations were computed through use of the U .S. Army Corps <br /> <br />of Engineers' HEC-2 step-backwater computer program (Reference 6). Cross <br /> <br />sections for the backwater analyses of the White River and Sulphur Creek were <br /> <br />field-surveyed at close intervals above and below bridges and culverts in order <br /> <br />to compute the significant backwater effects of these structures. Additional <br /> <br />digitized cross sections were secured when the topographic maps were compiled. <br /> <br />The locations of the cross sections are shown by reference points on the flooded <br /> <br />area maps and the flood profiles. The reference points, 100-year flood elevations <br /> <br />and discharges are also listed in Table lA, pages 17, 18, and 19. <br /> <br />Channel roughness factors (Manning's 'n' values) for these computations <br /> <br />were assigned on the basis of field inspection of the floodplain areas. <br /> <br />Hydraulic losses through the culverts on Sulphur Creek were computed with <br /> <br />the use of nomographs available from the Bureau of Public Roads (Reference 7) <br /> <br />and input into the HEC-2 computer program. <br /> <br />Because drainage from the Sanderson Heights area presently flows through <br /> <br />Meeker as shallow surface flow, no hydraulic calculations were necessary. The <br /> <br />path of the overland flow, estimated from the topographic mapping and site inves- <br /> <br />tigations, is shown on the topographic maps by arrows. <br /> <br />A detailed description of the hydraulic analysis is included in the Technical <br /> <br />Addendum. <br /> <br />16 <br />