The middle and lower course of the Chikusa River in Hyogo Prefecture, western Japan, was divided into three segments on the basis of the characteristics of its longitudinal profile and alongstream changes in channel slope. Further, quantitative analyses of sinuosity, excess segment index, and channel width, and grain size analysis of river bed sediments were performed in the same reaches. The results indicate that each segment is characterized by a different channel pattern and downstream change in grain size distribution, corresponding to the alongstream changes in channel slope . This can be explained rationally as follows ; the longitudinal profile representing the alongstream change in channel slope determines the alongstream change in tractive force. Further, grain size distribution and movement modes of river bed materials are determined by the tractive force, resulting in a change in channel patterns through deposition and/or erosion. Thus, it can be concluded that the alongstream changes in channel pattern are controlled by the characteristics of the longitudinal profile through the medium of the grain size distribution.
