A DRIFT WOOD HAZARD AND ITS COUNTERMEASURES IN STEEP SMALL-SCALE RIVERS

Abstract

In 2004, a sever drift wood hazard caused by fallen trees drifting in muddy flows and overflowing at river bridges happened in many steep small-scale rivers of Ehime Prefecture. In this paper, a countermeasure in which the rail on the bridge girder is removed and some of flowing flood water overflows on the bridge girder like a sinking bridge is proposed and the effect of the countermeasure is examined through runoff experiments in hydraulic steep channels. As a result, it was made clear that the countermeasure removing the rails is a very effective one which reduces a destructive power of overflooding water to one third.