BED TOPOGRAPHY AND SORTING IN BENDS.

A mathematical model for defining the bed topography and the bed material size distribution in uniformly curved bends of alluvial rivers is developed, in which the coarsening of sediment size toward the outside bank is predicted and the bed topography is calculated coupling with the lateral sorting. The major agency for the sorting is that coarser grains feel a larger ratio of transverse gravitational force to fluid force than finer grains. It is revealed that the sorting reduces the depth of scour considerably in the outer area of bends. The model is tested with a laboratory test, and it is applied to an actual river, both of which support the current theory.