ANALYSIS OF DRIFTWOOD BEHAVIOR AND ACCUMULATIONS ON SANDBAR CONSIDERING FLOOD FLOW AND DISCHARGE

Field surveys, experiments and numerical calculations were conducted to examine driftwood accumulation in a river channel, with respect to the existence of sandbars. We investigated the areas where driftwood accumulated and captured from river channel is observed in two rivers. It seemed that factors such as the existence of riparian woods, sandbar configurations, and sandbar locations relative to the river flow determined the points of driftwood accumulation. Based on the field survey results, hydraulic model experiments investigated the flow path of driftwood in model river with alternate sandbars. The analysis related to flood flow indicates that when the flow velocity and the water depth of the main current differ greatly from the flow velocity and the water depth of the flow that is away from the main current, the force of the main current acting on driftwood pushes the driftwood outward. And we clarified the relationship between discharge and the locations of driftwood capture, traps were built at different points on a sandbar.