EFFECTS OF CHANGE IN RIVER WIDTH ON KNICKPOINT RETREAT IN BEDROCK RIVERS

Abstract

 After the disappearance of sediment, bedrock exposure and erosion progressed, and knickpoint was formed at Toyohira River Oiranbuchi. In this study, we attempted to elucidate the erosion process of bedrock rivers with change in river width and slope using a numerical model that considers bedrock erosion. Numerical experiments were performed by changing the river width and discharge. As a result, it was suggested that the change in the river width around the knickpoint increased the amount of sediment transport and it made the amount of bedrock erosion, which promoted the retreat of the knickpoint. In addition, the dry-wet weathering flattened the upstream bedrock and retreated the entire steep slope, suggesting that the effect of the change in river width on the knickpoint retreat was maintained.