直線流路の側岸侵食機構

Abstract

According to the observation of experiments in lateral erodible straight channels, the pro-cess and mechanism of bank erosion is investigated by the way of following procedure. First, con-dition of collapse of upper part of eroded bank is clarified by the moment blance and a experi-mental result of the distribution of sand included in collapsed part is shown. Then, representa-tive profile of wetted perimeter of side s1ope region and its hydraulic characteristics are derivedfrom abundance of dimensionless cross-sectional shapes in straight channels, and this profile de-termines the scour zone, where bed degradation is most effective to bank erosion or collapse.Consideration of the movement of sand grains in this zone leads to the conclusion that degradationrate is mainly controlled by stationary lateral migration of the amount of sand estimated byBagnold's consideration introduced side slope effect. Finally, the expression of the bank erosionrate at constant water level is obtained and the erosion rate evaluated by this equation agreesfairly well with observed one. Moreover it is pointed out that accuracy of this expression isimproved if the coefficient is adequately varied according to flow resistance.