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<br />The hydraul ic characteristics used in equation 10 are defined <br /> <br />below: <br /> <br />Friction slope, s~mog ~,J.7trri\:'p ,..l......~ or energy <br />~ <br />slope of the energy 1 ine of a body of flowing water. <br /> <br />gradient is the <br />..) <br />The Manning <br /> <br />equation was developed for conditions of uniform flow in which the water <br /> <br />and friction slope or energy gradient are parallel. The slope should be <br /> <br />representative of <br /> <br />l)"r~ <br />slopes ~ several <br /> <br />the channel and can be estimated by averaging the <br />c":-tAN.'if:..:.:- S <br />ressRe.... vr dlrr~,....lIl width" This condition is met <br /> <br />because the correlation coefficient relating water slope and friction <br /> <br />slope is 0.99. Therefore, values of the water slope and friction slope <br /> <br />can be used interchangeably in equation 10. <br /> <br />Hydraulic radius, R, is a measure of the boundary area causing <br /> <br />friction per un; t of flow and is computed as the perpendi.cuJar c.ross- <br /> <br />$f <br /> <br /> <br />sectional area of a stream of water divided by the channel wetted <br /> <br />perimeter. Cross-section area and wetted perimeter are obtained from <br /> <br />field surveys. In standard practice, the wetted perimeter does not <br /> <br />include the length of wetted contact between the water and the streambed <br /> <br /> <br />particles. Hydraulic depth, D, the cross-sectional a(ea divided by the <br /> <br />top width could also be used in place of hydraulic radius because the <br /> <br />correlation coefficient relating hydrual ic depth and hydraul ic radius is <br /> <br />0.99. <br /> <br />