In order to stably maintain a river channel, the river channel form needs to suit its origin. Therefore, many researches on the origin of the plane form of a river channel or river width have been conducted. However, the relation between a channel network and meandering shape or a sandbar and the formation process of a channel network is not sufficiently clarified. In this research, in order to clarify these phenomena, a hydraulic model experiment using a wide width flume was conducted and the results were discussed using meandering theory and bar formation theory. As a result, it has been shown that the bars and braided channels may be influenced to some extent by the wave resulting from plane instability.