Sediment and Geomorphology Differentiation of Tidal Flat Profiles  Combined Wave and Current Actions:a case of the east  Chongming tidal flat, Changjiang Estuary

Key words: 
• Changjiang Estuary /
• east Chongming tidal flat /
• tidal flat profiles /
• surf zone /
• microgeomorphic units

Abstract: Based on the data of two tidal flat profiles, surface sediment and suspended sediment grainsize, current velocity and suspended sediment concentration in the east Chongming tidal flat, the sediment and geomorphology differentiation of tidal flat profiles combined wave and current actions were analyzed. The results showed that the surface sediment D50 decreased gradually from the surf zone to the near shore and outer sea. The sorting of the surface sediment increased, and the skewness changed from very positive to positive, and the kurtosis changed from very leptokurtic to platykurtic and mesokurtic. The current velocity decreased and the suspended sediment concentration increased from the surf zone to the near shore. The comparative analysis of suspended and surfacial sediment grain size showed that the suspended sediment in the upper of intertidal zone mainly came from the sediment resuspension of the surf zone. The selective transport due to the sediment uplift by wave dominated the sediment transport in the surf zone, and the sediment horizontal transport by tidal current dominated the sediment transport in the near shore and outer sea beside the surf zone. The microgeomorphic units of east Chongming tidal flat were divided based on the discussion of the water level and accurate elevation recently.