An Evaluation of Methods for Calculating the Concentration of Suspended Bed Material in Rivers

A modified Rouse equation is used to predict the average concentration of suspended bed material in rivers and canals with sandy, dune‐covered beds. Equations of Einstein, Itakura and Kishi, and Engelund and Fredsoe are used to calculate the absolute concentration near the bed, Ca. Calculations based on the Engelund‐Fredsoe equation are consistently about 31 times too high. A modified Einstein equation overpredicts high concentrations and underpredicts low concentrations. The median predicted con‐ centration is only 20% too high, however. The Itakura and Kishi equation is the most successful theory; predicted concentrations are overestimated by only 50% on the average. Better results, however, are obtained using a constant value of 22,258 ppm for Ca in the Rouse equation, suggesting that Ca varies within a much smaller range than is predicted by current theories. A simple regression equation (r = 0.88) for the average concentration is also obtained. The regression equation is the most successful of all of the methods tested here.