砂州形成区間における瀬-淵構造の形態的特徴とその規定要因

抄録

Riffle-pool structure is an important factor for river ecosystem. At the same time, the characteristics of riffle pool structure represents the condition of sediment transport dynamism in the river. Against such a background, type of riffle-pool structure was classified into two types thorough field measurements and the mechanism how the different type of riffle-pool structure is formed was analyzed. Based on the observations in the Aki River and the Iruma River, it was clarified that riffle-pool structure whose water surface width is constant in flow direction is formed in the area with thin sedimentary layer. On the thick sedimentary layer, usual riffle-pool structure that was formed by concentration and diversion of flow was observed. Moreover, even if the sedimentary layer is thick, gravel bars with low disturbance have the constant width type riffle-pool structure in the Nakatsu River. By carrying out flume experiments, it was clarified that constant width type riffle-pool structure was created when the interaction of strong water flow between thalweg and dry riverbed disappeared.