Hydrodynamic process and sediment transport in a tidal creek system over the Easten Chongming Island, Yangtze Estuary

To speculate about the hydrodynamic process and sediment transport within the intertidal zone, we conducted a two-day survey in the Eastern Chongming Island in April, 2014 during a spring tide. Four tripods were deployed in three main morphological domains: one in the sat marshes, one in the mudflats and two in the tidal creeks. Our results show that: (1) the median particle size of surficial sediment in the creeks is 21. 7 /im and is finer than that in the sat marshes and mudflats which is 33. 0 /im. The particle size of suspended sediment decreases landward; (2) the dominant currents are rectilinear currents in the tidal creeks while are often rotational flows in the flats. The average vertical velocity in the lateral, creek, sat marsh, and mudflat is 1 5. 4 cm/s, 34. 6 cm/s, 11. 3 cm/s, and 28. 9 cm/s, respectively; (3) the highert suspended sediment concentration appears in the early flood periods in the tidal creeks while occurs during slack water or in the middle of the ebb periods in the flats. The suspended sediment in the tidal creeks mostly derives from adjacent sea rather than resuspension which is the main suspended sediment source in the flats; (4) over a tidal cycle, net landward sediment transport is observed in the creeks and the average sediment flux per tidal cycle could be 4. 0 t/m. There is also a net import of sediment with 1.0 t/m per tidal cycle driven through the sat marsh. On the contrary, the net sediment flux in the mudflat is seaward along the creek and the dominant sediment transport in the mudflat is perpendicular to the creek rather than along the creek which the lateral, creek and satt marsh are. Our results also indicate that the satt marshes experience deposition while the mudflats are eroded in our study site.