Program

An 11-tidal-cycles time series of current, wave, suspended-sediment, and bed-level characteristics were analyzed to identify physical and sedimentary processes on the tidal flat of Jiangsu Coast, China. A tripod observation system was placed on the upper to middle flat south of a new constructed harbor for hydrodynamic and sediment dynamic measurements from 27 Apr 2013 to 3 May 2013. The observations confirm the stable longshore northward (ebb direction) current velocities and the strong residual velocities about 59.2° anti-clockwise from the offshore direction. This phenomenon can be attributed to the effects of headland (the Harbor) induced tidal eddies with the comparable frictional length scale and the headland length scale. Benthic fluid mud layers occurred in 2 of 11 tidal cycles, with the conditions of strong waves during the flood phase. The fine sediment resuspended by the waves and currents from the lower area converged at the observation station, resulting in the formation of benthic fluid mud layer with thickness of ~ 20 cm and SSC of ~ 8 kg/m³ at 10 cm asb. Once it formed, the fluid mud layer dramatically modified the flow structure, showing a large reduction of current speed from 20 cm asb to 10 cm asb, and the gradient Richardson number was around the critical value of 0.25, allowing the generation of sufficient turbulence from waves and currents to maintain the fluid mud suspension. The fluid mud processes appears to occur episodically and may play an important role of sediment dynamics on the tidal flat.