Observation and analysis of hydrodynamics in a tidal creek at the Chongming Dongtan salt marsh

Based on the multiple observation methods,we conducted a field study at the Chongming Dongtan salt marsh in July 2007.The collected data is analysed systematically in this paper.The observation results show that (1) Time variation of the creek water level at field site is different from that of the coastal sea,which might be affected by the damping of the creek and marsh surface.The rising phase is steeper than the falling phase one.During the ebb period of the creek current,the rise of the local water table is not likely related to the tidal water entering creek.It banks up while the ebb creek water met the rising tidal water.(2) Wind plays an important role in hydrodynamics of the salt marsh.While the tidal wave is entering inner marsh,the shoreward wind will updrive water table compared with the offshore wind.(3) The creek current velocity is not strongly related to the rate of water level changes in the creek or the rate of the coastal tide fluctuation.And (4) the wetted cross-sectional area of the creek is relatively small,while little water is in the creek.Once the reversal creek current occurrs,one creek current velocity surge turns up.Due to the expansion of the wetted cross-sectional area,a creek current velocity surge exhibits as the creesk water spills out to marsh surface.The creek water level descreases slowly during the ebb tide.No creek current velocity surge presents as the marsh surface water flows into the creek.Finally,this paper summarizes the factors affecting hydrodynamics in the salt marsh,and gives the suggestions on the future works.