关键词: 河道演变, 冲淤分析, 三峡工程, 分汊河段, 荆江

Abstract: The operation of the Three Gorges Project has significantly alleviated flood control pressures on the Jingjiang River and altered water and sediment dynamics along its course, leading to continuous and substantial erosion and sedimentation changes in the river. The Chenjiawan-Tuqi sandbar reach in the Jingjiang River represents a prototypical gently curved braided channel, where adjustments to the beach and primary branch patterns directly impact channel operations and flood mitigation measures. By analyzing long-term hydrological data and channel topography prototype observations before and after Three Gorges Project operation, we revealed the variations in water and sediment transport within the reach and the riverbed’s responses to erosion and sediment deposition. Furthermore, we examined the interannual morphological changes and scales of the channel,and summarized its evolving regularities and trends. Results indicated an 85% reduction in average annual sediment transport at Shashi Station after Three Gorges Project operation, with an erosion of 310 million cubic meters of riverbed material. The most pronounced beach changes occurred from Taiping estuary sandbar to Sanba sandbar braided reach, prompting a shift in the main flow direction from north to south. Subsequent to the 2011 implementation of the Sanba sandbar and Lalin sandbar beach protection project, the trend of “southward movement of Taiping Estuary sandbar south of the main channel and northward movement of Sanba sandbar south branch” has been largely mitigated. However, ongoing adjustments in this river section have resulted in a new pattern characterized by “northward expansion of the south deep trough and southward expansion of the south branch”. The increasing development along the south branch of the Sanba sandbar and reduced diversion ratio on the north branch have raised navigation concerns near the Yangtze River Bridge. Further investigations are necessary to address the navigation obstruction effectively.

Key words: channel evolution, deposition-scouring analysis, Three Gorges Project, braided reach, Jingjiang River