Understanding the characteristics of erosion and deposition in river bends helps predict bank evolution

and guides flood control safety

efficient water resources utilization

and navigational channel maintenance. Erosion-deposition patterns in a river bend are typically characterized by concave erosion and convex deposition. However

following the Three Gorges Reservoir impoundment

multiple sharp bends in the lower Jingjiang River shifted to the anomalous pattern－convex erosion and concave deposition. This study examines this anomalous phenomenon through numerical simulations of erosion and deposition in the river section from the Qigongling bend to the Guanyinzhou bend in the lower Jingjiang under the conditions of multiple flow regimes. The results indicate that the reservoir operation leads to longer water flow duration and a sharp decrease in sediment inflow

causing the main flow axis to shift towards the convex bank and the river section to shift to the anomalous pattern. Under medium and high flow levels

the erosion zone is highly consistent with the high-velocity main channel. As the flow level rises

the mainstream path deviates towards the convex bank

and the erosion there intensifies accordingly. Sediment concentration and its variation play a regulatory role in erosion-deposition intensity. Under the same flow level

a significant decrease in the concentration strengthens erosion

while an increase promotes deposition. We have obtained the concentration thresholds as a switching condition between erosion and deposition under different flow levels. This study gives a preliminary clarification of the synergistic mechanism of flow level and sediment concentration underlying the spatial distribution and intensity of sedimentation

laying a basis for understanding the evolution of curved river channels downstream of reservoirs.