A STUDY ON EROSION RISK OF STEEP SLOPE RIVERS CONSIDERING FLOW RATE AND RIVERBED FLUCTUATIONS ASSOCIATED WITH CLIMATE CHANGE

This study aimed to analyze the erosion risk based on time-series changes in flow rate and riverbed changes in rapidly flowing rivers under climate change. The Toyohira River, the subject of this study, is a rapidly flowing river that flows through the urban area of Sapporo and is prone to erosion due to high-speed flood flow. In this study, in order to take into account the uncertainty of climate change, runoff calculations were conducted using a large amount of ensemble rainfall data obtained from d4PDF. Next, a riverbed fluctuation calculation was conducted for each event to estimate the time-series changes in riverbed fluctuations and erosion risk. Finally, a cluster analysis of the present and future spatial distribution of rainfall was conducted to determine the spatial distribution of rainfall that is likely to cause significant flood damage. The results show that the magnitude of erosion risk varies temporally and spatially depending on the characteristics of the runoff, and suggest that erosion risk tends to increase when the rainfall is concentrated in the middle part of the Toyohira River.