During big floods, the river bed near Tongguan erodes, while in small floods, it remains stable. The amount of water flow and sediment determine if erosion occurs. Most big floods cause slight erosion, but those with high discharge lead to significant erosion. Small floods with high sediment concentration can actually raise the river bed. Recently, Tongguan has experienced more small floods with high sediment, leading to less erosion during flood periods. This has caused the elevation to rise annually.