Mechanics of Stable Straight Channel or Braided Channel Formation

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The process in which a straight channel reaches a stable equilibrium state was investigated. The process is classified into a following two categories ; (1) channel widening process due to a bank erosion in case that the initial channel width is larger than the stable one, (2) channel narrowing process due to a sediment deposition around a water margin which is caused by the unsteadiness of water discharge. Such two processes were reported through the field investigations by the researchers in Public Works Research Institute, Ministry of Construction, Japan. In this study, the processes were simulated in an experimental flume. Numerical simulation model was also constructed to understand the process itself.The process in which a braided channel network forms was also investigated. Channel network formation on a bare slope as well as a braided river formation in a flume was studied experimentally with a focus attention on the similarity between these two processes. The mechanism was understood. For example, subsurface flow plays an important role in such formation. Some other interesting information was also obtained. Besides the experimental investigation, numerical model was developed in some limited conditions. This will be extended in more sophisticated version in future.The mechanisms of the above two processes were made clear as the author expected in the initial plan.