EXPERIMENTAL STUDY ON SINK MOTION OF DRIFTWOOD AND CRITICAL CONDITION FOR DRIFTWOOD BLOCKING

Abstract

At the time of heavy rain, driftwood accumulates at river infrastructures and blocks a river. Driftwood accumulation results in an increase of backwater. It is well known that driftwood sinks under the water surface and the entire depth region is blocked. However, there is almost no detailed information about the porosity of wood jam and the mechanism that driftwood sinks under the water surface. In this study, two kinds of flume experiments were performed. First, driftwood accumulation experiments at a two-pier bridge were conducted. We examined the effect of the approach flow velocity, approach flow depth and specific density of driftwood on the porosity of wood jam. Then, we conducted PIV measurement to examine the effect of the downward flow on the driftwood accumulation. The experimental results revealed the critical condition for driftwood blocking.