DEGRADATION AND WIDENING PROCESS OF GRAVEL RIVER UNDER THE CONDITION OF NO SEDIMENT SUPPLY AT UPSTREAM END

Abstract

Channel forming process under the condition of no sediment discharge was investigated with both flum experiments and numerical simulations. In addition to the degradation of bed -elevation, natural channel can change its width relatively within short time, in the process. The experimental results revealed that the relatively short time for channel widening firstly occurs, and then the bed-slope gradually adjusts to the static equilibrium condition with no significant change of the channel width. The numerical model to simulate the channel forming process, which is constituted by the depth-averaged 2-D flow model with the non-orthogonal boundary fitted grid system and the bed -deformation model taking into account the collapse of the bed -material on side banks, can reproduce the process observed in the experiment.