Author(s): N. Kimura; A. Tai
Linked Author(s): Akira Tai
Keywords: Smoothed particle hydrodynamics; Bridge; Flooding; Extreme weather
Abstract: Extreme weather has occurred more frequently worldwide over the last decade because of climate change. Therefore, at times, very heavy rains have caused severe flooding in the world. There have been reports of uncommon floods (such as flooding caused by the substantial accumulation of driftwood or debris) at a bridge in mountainous areas in southern Japan. To reduce a flood-induced disaster of this kind, it is necessary to better understand the flood mechanism. In this study, smoothed particle hydrodynamics method was employed to simulate flooding in the two-dimensional vertical plane. The method could reveal the physical processes of a driftwood-induced flood event at a river bridge. As the first step, we focused only on the effect of a bridge on water flow without driftwood. Open software, SPHysics implementing smoothed particle hydrodynamics method, was calibrated with data of water level recorded at a miniature bridge in our laboratory experiment. Like the laboratory experimental result, the calibrated simulation result clearly showed that the flow was divided into a top surface flow above the bridge girder and an undersurface flow below the bridge girder and the water level gradually was raised in an upstream direction from the bridge. In addition, using the SPHysics, we assessed how the bridge characteristics (for example, the width and thickness of the bridge girder and the spacing of cross sections) affect the intensity of flooding. A shorter thickness and lower position of the bridge girder caused larger dam-up water levels. This suggests that there is potential flooding at a bridge even without driftwood.
Year: 2014