Abstract
A heavy rain fall hit Shobara city, Hiroshima on 16th July 2010. A large amount of woody debris caused a flooding disaster by damming up a bridge and spreading out to rice field and so on. This paper presents an inquiry on the shape properties of the woody debris left on the rice field. And simulations of the damming up process of woody debris occurred on the real bridge by using 3 dimensional Distinct Element Method based on assembled cylinder elements. The simulation points out the twisting mechanism of woody debris occurred at the space between slab of the bridge and the flood surface in damming up process. Validity of the simulation at real site is discussed.
