ASSESSMENT OF DRIFTWOODS HAZARD RISK IN THE HOSHINO RIVER BASED ON EXPEMENTAL DRIFTWOODS TRAP RESULT AT STONE BRIDGE

In this paper, we attempted to refine the evaluation method of woody debris hazard risk at a stone bridge developed by Yano et al. (2017), using model hydraulic experiment results. From the result of experiment, it is clarified that a half width of span length can be used as the representative length scale of stone bridge arch structure. Adapting the new evaluation of driftwoods accumulation at a stone bridge, driftwoods hazard risks are assessed in the Hoshino River. It shows that most stone bridges indicate a large risk.