Estimation Of Drift Woods Discharge From A-Class Rivers In The Ariake Sea By Their Numerical Transport Simulation

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Shinichiro Yano, Yohei Kitagawa, Hiroaki Taniguchi, Keisuke Nishimura, Shunta Dozono

Thursday 2 july 2015

12:30 - 12:33h at Amazon (level 1)

Themes: (T) Water engineering, (ST) River and coastal engineering, Poster pitches

Parallel session: Poster pitches: 11B. River Engineering

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Woody debris in flood event can cause inundation due to accumulation on a bridge; collapse of a small bridge, and so on. Drift woods discharged into a coastal area can also cause disturbance in function of port, restriction of small fishery boat navigation, disorder of cultivation facilities, and so on. Thus, it is strongly required that risk management of drift woods disaster in overall area from a mountainous river basin to a coastal area. So-called “the Northern Kyushu Heavy Rain in July, 2012” in Japan caused very serious damages in Kyushu area, such as more than 30 victims and big economic loss. The event also caused many drift woods disasters in river basins and coastal areas. This research focuses on transport of drift woods in the Ariake Sea due to the rain event. Numerical simulation of their transport by 3D hydrodynamic model (DELFT3D) combined with assumed drift woods tracking model and comparison between the calculation result and collection data by Ministry of Land, Infrastructure Transport and Tourism were conducted. From the result, the followings were clarified: 1) total drift woods volume of discharged from all rivers into the sea was estimated as 17,500m3; 2) volume of discharged drift woods from each A-class river was estimated; 3) relationship between the volume and specific maximum river discharge was evaluated.