An MIDAS-400 Customised Data Ac- quisition System was deployed to obtain current ve- locity and suspended sediment concentration profiles over the intertidal flat at Wanggang, on the Jiangsu coast (China). At the same...An MIDAS-400 Customised Data Ac- quisition System was deployed to obtain current ve- locity and suspended sediment concentration profiles over the intertidal flat at Wanggang, on the Jiangsu coast (China). At the same time, seawater tempera- ture, conductivity and pressure were measured. Us- ing a data sampling rate of 4 Hz, the high-frequency pressure signals in response to water surface fluc- tuations were recorded and subsequently trans- formed into wave parameters. The analytical results show that the apparent bed roughness length has a magnitude close to the height of sand ripples, which is much larger than the grain size diameter. The bot- tom shear stress associated with current-wave in- teraction is higher than the tidally-induced stress and intensified turbulent mixing and resuspension. Fur- thermore, several suspended sediment concentration peaks occurred during a tidal cycle, which can be related to strong turbulence near the bed caused by frontal tidal currents and the enhanced resuspension; advection and extreme weather conditions (e. g. storms and strong winds) also played an important role. Finally, large net suspended sediment fluxes were observed to present when the flood or ebb currents prolonged, i.e. the flow became quasi-unid- irectional during a tidal cycle. In general, the MIDAS- 400 is a suitable tool for high-resolution data collec- tion for the situations of combined current-wave ac- tion over intertidal flats; the data obtained can be used to analyze the processes and mechanisms of material transport.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.40576040,40231010 and 40206006).
文摘An MIDAS-400 Customised Data Ac- quisition System was deployed to obtain current ve- locity and suspended sediment concentration profiles over the intertidal flat at Wanggang, on the Jiangsu coast (China). At the same time, seawater tempera- ture, conductivity and pressure were measured. Us- ing a data sampling rate of 4 Hz, the high-frequency pressure signals in response to water surface fluc- tuations were recorded and subsequently trans- formed into wave parameters. The analytical results show that the apparent bed roughness length has a magnitude close to the height of sand ripples, which is much larger than the grain size diameter. The bot- tom shear stress associated with current-wave in- teraction is higher than the tidally-induced stress and intensified turbulent mixing and resuspension. Fur- thermore, several suspended sediment concentration peaks occurred during a tidal cycle, which can be related to strong turbulence near the bed caused by frontal tidal currents and the enhanced resuspension; advection and extreme weather conditions (e. g. storms and strong winds) also played an important role. Finally, large net suspended sediment fluxes were observed to present when the flood or ebb currents prolonged, i.e. the flow became quasi-unid- irectional during a tidal cycle. In general, the MIDAS- 400 is a suitable tool for high-resolution data collec- tion for the situations of combined current-wave ac- tion over intertidal flats; the data obtained can be used to analyze the processes and mechanisms of material transport.
