Abstract
Bedrock exposure and erosion have caused the deterioration of the river structure's stability in many rivers. Previous studies reported that the collision of bedload is one of major factor controlling bedrock erosion. Furthermore, bedrock erosion has been concerned with wet-dry weathering and freeze-thaw. The bedrock erosional morphology can be classified into valley type, single water route type and multiple longitudinal groove type from the relationship between alluvial cover rate and bedrock strength. We conducted the needle penetration tests at the upstream of Oiranbuchi in Toyohira River where bedrock widely exposed. It is confirmed that the influence of weathering by wet-dry cycles due to tendency of low bedrock strength at the water's edge. In this study, we constructed the bedrock erosion model considering of wet-dry weathering and carried out the numerical simulations to evaluate the erosion morphology by weathering. The results suggest that bedrock is smoothed when erosion by weathering is dominant and bedrock incision progresses when abrasion by bedload is dominant.
