Field measurements are made of time series of tidal elevation, current velocity, salinity and suspended sediment concentration at three hydrological gauging stations CS1, CSW and CS8, within the curved three hydrological gauging stations CS1, CSW and CS8. Strain induced periodical stratification is predominant at these locations. It is found that the tidal straining is the key mechanism for the stratification within the waters of the curved channel. The rate of change in the potential energy dut to estuarine circulation is smaller than that dut to tidal straining and tidal stirring by the order of 102 ~ 103. navigational channel of the north passage of the south branch/south channel of the Changjiang River estuary, on spring, moderate and neap tides, on 1 to 10 January 2010. Those data display the spring/neap and flood/ebb tidal variability in the vertical stratification caused by salinity and suspended sediment concentration.To quantitatively evaluate the potential of vertical mixing within the curved channel, we estimate the gradient Richardson number (Ri) using the density of water after taking suspended sediment concentration into account. Ri at stations CS1 and CSW can be in the order of 101 ~ 102 at the turning of the tide. The strongest mixing with the order of 10-2 ~ 10-1 occurs at the maximum flood and ebb tides. Ri at station CS8 is between 0.25 and 5 at the flood tide and of the order of 10-2 at the ebb tide. At the three hydrological gauging stations, stratification appears to be stronger at the flood tide than at the ebb tide. Stronger stratification is present on the spring tide, while stratification lasts longer on the neap tide.Following Simpson, we estimate the rate of change in the potential energy of the water column within the curved channel caused by tidal straining, estuarine circulation, and tidal stirring. Tidal straining is present at the