Experimental Study on Stream Channel Processes in Alluvial Rivers

Abstract

In order to elucidate fluvial processes of alluvial rivers, experiments were carried out in the 7.5m wide flume of Experimental Facilities for Research of River Disaster in Ujigawa Hydraulic Laboratory of the Disaster Prevention Research Institute. In the beginning of the experiments, the stream channel was widened uniformly in longitudinal direction and the channel bed was raised by depositing eroded sand from side banks, and after a while, signs of alternating bars appeared on the bed. And then, channel widening and bed variation were affected by boundary conditions to have a obvious longitudinal change, though planform of channel was still straight, while alternating bars kept on developing and traveling. But channel processes after that became considerably different from each other, being governed largely by experimental conditions which were classified into three groups, and consequently, three kinds of channel patterns were formed, that is, meadering channel, braiding channel and straight channel with armor coat. In addition, it was indicated that there were not a few common aspects in fluvial processes to every experiment under different conditions, and based on these aspects, a diagram explaining the stream channel processes under fundamental conditions was presented.