Field study of the physical regularities of sand suspending under breaking waves

The mechanisms and time scales of sand suspension by irregular waves are considered on the basis of field experiment "Norderney’94", performed in the North Sea. The suspended sediment concentrations and the fluid velocity components were recorded synchronously by optical and electromagnetic gauges. The sensors had been installed in a distance of four to fifteen centimeters above the bottom at the depth range from 0.5 m to 2.2 m in the surf zone.The observed data testify to the fact, that the both turbulent and wave components of vertical velocity determines the suspended sand flux from the bottom. The vertical sand flux is remarkable at the moments of wave breaking and is insignificant during the other times. The time scales of the turbulent kinetic energy and of the shear stress near the bottom define the time scales of the suspended sediment concentration fluctuations

Keywords:

sand suspending , breaking waves , sand transport , surf zone turbulence