Analysis of Sacramento River Bend Flows, and Development of a New Method for Bank Protection
2006
Odgaard, A. J. | Kennedy, John F.
This study includes an investigation of analytical models for the description of flow and bed charactersitics in a bend of the Sacramento River, California; and a study of a proposed new technique for bank protection. Existing models for the prediction of the steady-state transverse bed profile in channel bends are reviewed; and alternative models are developed and validated. The new models predict the transverse bed slope to-vary linearly with d/r (the ratio of depth, d, to radius curvature, r) and almost linearly with the sediment-particle Froude number. Equations for the transverse variation of depth-averaged' velocity and mean-grain size also are developed, which, together with the equations for the transverse variation of depth, can provide a guide to the depth of bed erosion and depth-averaged velocity near the outer bank of river bends. It is shown, theoretically and by a physical model, that short, vertical, submerged vanes installed at incidence to the channel axis in the outer banks of a river-bend channel significantly reduce the secondary currents and the attendant undermining and high-velocity attack of the outer bank. The effect of the vanes on the secondary flow is estimated by a simple torque calculation using the. Kutta-Joukowski theorem. A design relation for the van spacing is derived by equating the torque, about the channel centroid, produced by the flow curvature to that resulting from the lateral force exerted on the vanes. The relation is verified in an idealized, physical model of the mentioned bend of the Sacramento River, Calif.
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