網状流路における混合砂礫の分級と流路変動

Abstract

Braided channels are generally produced in mountain streams with very active sediment yields.Such channels vary spatially and temporally, which results in a big variation of the sediment discharge.The bed material is composed of a wide range of grain size, which brings about sediment sorting.Channel variation and sediment discharge are closely associated with each other.In this paper, discussions are made with attention focused on the relation between a channel process and sediment sorting. A flume test is conducted under a constant flow discharge and sediment supply rate with non-uniform sand. According to the results, a channel bifurcation occurs always in a diverging phase or a widenning process of the channel, accompanying with transverse and lateral sediment sortings as well as with a rapid change of the bed slope.