Fluvial Process and Stability of Anabranching River Systems: Case of Jianli Reach in the Middle Yangtze River, China

Anabranching is a typical channel pattern developed in the middle and lower reaches of Yangtze River. However, the process of flow and sediment transport along these anabranching reaches varies significantly and yields considerable negative impacts on regional social and economic development. By analyzing the long-term process of flow and sediment transportation and allocation between branches in a typical two-channel river system located in the Jianli reach, this study have found that hydrologic regime is the main reason for the main current translocation between two branches and thus cause planform adjustments. Left bank instability causes varied hydraulic geometry and water-sediment allocation between two branches when the left branch is the main channel. Erosion-resistant right bank results in stable cross section and water-sediment distribution when the right branch serves as the main branch. It indicates that the fluvial process of anabranching system is determined by the hydrologic regime and boundary condition. This study may provide insights into the understanding of the anabranching fluvial processes in Yangtze River and implementation of anabranching river regulation in the near future.