Flume experiments on log accumulation at the bridge with pier and without pier

Heavy rain causes landslide and debris flow, which produce sediment and woody debris in the mountain river basin. During the process, woody debris and sediment are trapped by the obstacles. As a result, woody debris accumulations at bridges are formed. Trapped woody debris at the bridge caused inundation because the obstacle blocked the water flow in the river course. To get more information regarding the woody debris accumulation at a bridge, laboratory flume was used for experiments to investigate the characteristics of woody debris accumulation at a model bridge without a pier. As a result, the experiments show that the number of trapped wood pieces increases with the number of released pieces. Moreover, the trapped wood pieces caused wood accumulations at the model bridge and backwater rise in its upstream side region. Besides that, the backwater rise increase with a number of trapped wood pieces at the bridges.