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<br />21 <br /> <br />Equations (2-26) and (2-28) are solved for two unknowns, Q and H, by an <br />iterative method. Note, however, that in this NRC study, a simpler method of <br />computing the water-surface profile, using the energy equation, was utilized <br />instead of solving the unsteady equations, (2-26) and (2-28). A standard step <br />method similar to that incorporated into HEC-2 was util ized in solving the <br />energy equation. <br /> <br />4. Sediment-Transport Equation: <br /> <br />The following formula developed by Graf (1968) was used to compute the <br />bed-material discharge for the San Dieguito River and the Salt River: <br /> <br />1/2 <br />CVR/((s - l)gd1/3) = 10.39((s _1)d/(SR))-2.52 <br />s s <br /> <br />.... (2-29) <br /> <br />where <br />C = mean volumetric concentration of bed-material sediment <br />s = ratio of sediment specific weight to water specific weight <br />s <br />d = median sediment size <br />S = energy slope <br />V = mean flow velocity <br />R = hydraulic radius <br /> <br />The Engelund-Hansen formula (1967) was used for the San Lorenzo River to <br />compute the total-load discharge: <br /> <br />. 2 1/2 2 3/2 <br />qT = O.OSrs V (d/g(Ysh-1)) (pu* /(ys- y)d <br /> <br />....(2-30) <br /> <br />where <br /> <br />qT = total-load discharge per unit width <br />Ys = specific weight of sediment <br />y = spec i fi c wei ght of water <br />u* = shea r ve I oc ity <br />p = density of water <br />