Influence of Continuous Sedimentation on the Flow Characteristics of Meandering Reaches: A Case Study of the Huanghuacheng Reach in the Three Gorges Reservoir, China

ABSTRACT Flow in a meandering river exhibits complex dynamics, particularly in meandering reaches within reservoir areas. This study focused on the Huanghuachang (HHC) Reach, a typical meandering reach in the Three Gorges Reservoir (TGR). Utilising a three‐dimensional hydrodynamic model developed in OpenFOAM, this study compared the flow characteristics in the HHC Reach before and after the TGR impoundment. The results revealed that the impoundment of the TGR significantly decreased the flow velocities across the HHC Reach as a whole. At flow rates of 20 000 and 40 000 m 3 /s, the maximum depth‐averaged flow velocities were reduced by about 59.4% and 31.4%, and the velocity reduction was particularly pronounced in areas identified as key zones for sediment deposition. Furthermore, both the secondary flow strength and turbulent kinetic energy were substantially weakened after the impoundment. While circulation structures at various cross‐sections facilitated the downstream transport of sediment, their near absence in key deposition areas was likely a primary factor contributing to the uneven distribution of sediment deposition across the HHC Reach. These findings not only enhance the understanding of hydrodynamic characteristics in natural meandering rivers but also offer references for management of the TGR and other fluvial systems.