2014 Volume 70 Issue 2 Pages I_777-I_783
Worldwide climate change has resulted in severe flooding in Japan in the last decade. Some floods were likely caused by the substantial accumulation of driftwood or debris at bridges crossing rivers in mountainous areas. In this study, for a two-dimensional open channel, we conducted a laboratory experiment and numerical simulation with and without driftwood modeling to clarify the physical mechanism of a flood event resulting from driftwood accumulation at a bridge. Open-source software SPHysics, implementing a smoothed particle hydrodynamics method, was calibrated with data of the water level measured near a miniature bridge in the laboratory experiment. The simulation clearly showed that the particle-like flow was scattered by the bridge girder and dammed up by the bridge in the upstream direction. By changing the quantity of driftwood, we analyzed the effect of a flood on a bridge. For the largest quantity of driftwood, the higher pressure pushing against the bridge may damage the bridge.
