Hydraulic model test on channel shifting and yielding woody debris on the fan after sediment disaster in the past

¹ Nippon Koei Co., Ltd., Research & Development Center, 2304 Inarihara Tsukuba-shi Ibaraki, Japan
² Kitami Institute of Technology, Civil Infrastructure Course, School of Regional Innovation and Social Design Engineering, 165 Koen-cho Kitami-shi Hokkaido, Japan
³ Aichi Institute of Technology, Department of Civil Engineering, Faculty of engineering, 1247 Yachigusa, Yakusa-cho, Toyota-shi Aichi, Japan

^* Corresponding author: a9456@n-koei.co.jp

Abstract

The re-movement of sediment and woody debris in torrents after huge sediment transport in the past could cause new flood and sediment disasters due to heavy rainfall events. However, it is not clear how re-movement of logs effects on bed variations such as bars and river channel divergence. In present study, hydraulic model tests were carried out referring to the magnitude of floods, that was over the plan size, in Tottabetsu River basin in August in 2016. These tests include different magnitudes of flood, suppling logs from bed/side bank erosion, and existence of sabo facilities. The key results were as follows: The presence of logs by bed/side bank erosions influences on the patterns of flows and sediment transport, because deposition of logs affects formation of bars. Difference of the magnitudes of the floods affects the activeness of the interaction between logs and sediment transport. In additions, the locations and slits of the sabo dam need to consider hydraulic conditions and characteristics of woody debris for appropriate control of sediment and woody debris.