2020年特大洪水作用下长江口南槽水沙输移特征

River discharge is one of the key factors affecting hydrodynamics and sediment transport in estuary. Previous field surveys and studies in the Changjiang (Yangtze) River estuary were mainly conducted for river discharge, and the discharge recorded at Datong Station is often <60 000 m³/s. However, estuarine dynamics under higher river discharge conditions remains poorly studied. In 2020, a large flood took place in the river basin and the peak volume at Datong reached 84 500 m³/s. We conducted a field survey in the South Passage of the river mouth in July 2020 when river discharge at Datong was 78 300 m³/s. The results show that the seaward water mass of the South Passage is well-mixed and stratified beyond the channel, which implies that high river discharge could mitigate salt intrusion. Historical data show that the average salinity was 75%, 82%, and 82% lower in 2020 than those under different river discharges of 9 900 m³/s (2013), 17 637 m³/s (February 2003), and 41 450 m³/s (2014), respectively, during spring tide; and 80%, 89%, and 91% lower, respectively, during neap tide. In addition, under river discharge of 9 345 m³/s (2004), 17 637 m³/s (February 2003), 41 450 m³/s (2013), and 60 877 m³/s (July 2003), the average concentration of suspended particles decreased by 63%, 62%, 70%, and 73%, respectively, due to long-term decline in riverine sediment carriage and dilution of larger river flow. This study enriches the understanding of estuarine hydrodynamics and sediment transport under extremely large river discharge, and provides basic knowledge for waterway and estuarine management.