Bed deformation in curved alluvial channels

Recent research activities at the Delft Hydraulics Laboratory and the Delft University of Technology have increased the understanding of the large-scale bed deformation in alluvial rivers with relatively stable banks. In this paper the most important results of these activities are given. First bed deformation in river bends is explained in the light of the results of some laboratory experiments in curved flumes with fixed banks. The deformation is then explained in terms of wave length and damping with a linear analysis of the water and sediment motion for the steady state. From this analysis the conclusion is drawn that the point bar height and pool depth in bends cannot be predicted solely from local conditions. A significant part of the lateral bed slope is due to an overshoot effect induced by the redistribution of the water and sediment motion in the first part of the bend. Finally the results of computations with a non-linear two-dimensional model, simulating three curved flume experiments, are discussed. The simulations of the experiments are in fair agreement with the data measured.