Author(s): Harada Daisuke; Egashira Shinji

Linked Author(s): HARADA Daisuke

Keywords: Landslides and debris flow; Driftwood; Watershed scale sediment transport; Hazard prediction

Abstract: Recent flood hazards occurring in mountainous areas are often characterized by numerous amounts of sediment and driftwood supplied from upstream, which often exacerbate flood disasters in downstream areas. In order to predict such hazards, methods to evaluate the amount of sediment and driftwood supplied from watersheds during heavy rainfall are required. In this study, we propose methods for evaluating sediment and driftwood runoffs from a basin, and apply the methods to the Terauchi Dam basin during the 2017 heavy rainfall in northern Kyushu to investigate factors affecting the sediment-drift wood runoff processes. The results show that the size or the bed slope of the upper most unit channel is a major factor affecting computation results, and placing the uppermost channel at about 10 degrees, where sediment deposition from the debris flow body begins, would provide reasonable results. These results mean that the sediment and driftwood supplies resulting from landslides and debris flows to the unit channels should be properly evaluated for predicting the sediment and driftwood transport processes in river basins.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p1247-cd

Year: 2023