Bed Characteristics in Alluvial Channel Bends

An approach to the description of the steady-state distributions of flow and bed characteristics in an alluvial channel bend is presented. The approach, which is based on a combination of the principle of moment-of-momentum flux and a critical-shear-stress analysis, is used to explain observed transverse variations of depth, depth-averaged velocity, and mean-grain size in a bend of the Sacramento River, California. The local transverse bed slope is found to vary linearly with d/r (the ratio of depth, d, to radius of curvature, r) and almost linearly with the bed-surface particle Froude number. It is established that the distributions of depth, depth-averaged velocity, and bed-surface sediment size depend on the variety of grain sizes in the bed sediment. Equations for the transverse variation of depth, depth-averaged velocity, and mean-grain size are developed, which can provide a guide to the depth of bed erosion and depth-averaged velocity near the outer banks of river bends.