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<br />)(vf")( --\\~J ~,,~~' <br />~\. \ <br /> <br />~ <br /> <br />Method <br /> <br />Milhous (1986) evaluates three method: shing flow <br />requirements (Tennant, Hoppe and effe( finds <br />them unsatisfactory because they do no cal <br />processes that affect the condition of suggests <br />an alternate method based upon the dimt__..,u~ess Shields parameter <br />and the d50 material size. Milhous uses the term Beta movement <br />parameter to distinguish it from the Shields parameter. The <br />Shields parameter describes forces sufficient to move the bed as <br />opposed to smaller forces required to flush fines from the bed <br />material. The Beta movement parameter is defined as <br /> <br />Beta = RS <br />(Gs-l)d50 <br /> <br />Where: R - hydraulic radiu~ ~ e v~} <br />w s E. + \f / _ W ~ +:;:-. <br />S energy slope ~ ~ <br />I ~-+-:cl <br />G - specific gravity of bed mater1al <br />s <br />d50 - median size of bed surface material <br /> <br />(armor layer) <br /> <br />A Beta movement parameter of 0.021 is required to flush fine <br />sediment from an armored stream and a value of 0.035 is needed if <br />the streambed is paved. The absolute minimum value for an armored <br />\ stream is 0.017 (Personal Communication, R. Milhous, July 7, 1987). <br />A movement parameter of 0.021 was selected as being necessary to <br />. <br />flush fines from the surface to the one-half diameter of the cobble <br />substrate at the Palisades site. ,Field studies at Oak Creek, <br />Oregon, which has substrate characteristics similar to the <br />Palisades site, support selection of a movement parameter of 0.021 <br />(Milhous, 1973). <br /> <br />5 <br />