AN EXPERIMENT AND NUMERICAL SIMULATION OF BEDROCK-EROSION CAUSED BY BEDLOAD ON BEDROCK

摘要

Bed degradation has been increasing rapidly in the upper part of the Ishikari River, owing to exposed bedrock erosion caused by bedload on the bedrock. In order to estimate the erosion velocity of bedrock, we performed an experiment by using a circular flume with artificial bedrock made of gypsum. This study also proposes a numerical model which can simulate the bed deformation process of rivers with bedrock to reproduce the bedrock channels induced by bedload. We incorporated the erosion velocity equation of bedrock and a bedload layer model into the plane two-dimensional morphodynamic model. The computational results show that the proposed model can simulate the development of bedrock channels by a concentration of bedload, and channel patterns in the simulation are similar to the channels which are generally observed on bedrock in real rivers. It was found that bed degradation progresses by erosion which is caused by sediment transport itself.