To analyze the similarities and differences in the water and sediment transport characteristics of the South Passage and the North Passage in the Yangtze River Estuary,we conduct a preliminary study based on synchronous hydrological observation data from the two passages during the 2019 flood season.The results show that the flow velocity in the South Passage exhibits higher upstream and lower downstream,whereas maximum flow velocities in the North Passage predominantly occur in its mid-lower reaches.Salinity in the mid-section of the South Passage demonstrate higher values compared to its counterpart in the North Passage,while salinity values in the South Passage from its lower reaches to the entrance are lower than the North Passage.Vertical-averaged suspended sediment concentrations(SSC)show comparable magnitudes between the two passages.Notably,the South Passage presents smaller vertical SSC gradients,with 2 kg/m3 SSC can be transported up to 0.2H(H is water depth).In contrast,high SSC in the North Passage predominantly concentrates in mid-bottom layers.The South Passage is wide and shallow,with a stratification coefficient ranging from 0.01 to 1,indicating a partially mixed state of the water body.In contrast,the North Passage is narrow and deep,and the salinity stratification coefficient is higher than the South Passage.The stratification coefficient in the middle-section of the North Passage is greater than 1,showing a high degree of stratification.Back siltation in the South Passage channel is influenced by both suspended sediment deposition and bedload transport.Under the influence of engineering activities,back siltation caused by suspended sediments in the North Passage channel is particularly prominent.