Ruben KOS’YAN - Head of Department SB IO RAS ۳۵۳۴۶۷ Gelendzhik - ۷, Russia
Nikolay PYKHOV - Leading researcher Nakhimovskiy prospectus ۳۶, ۱۱۷۸۵۱ Moscow, Russia.
Igor PODYMOV - Leading researcher SB IO RAS ۳۵۳۴۶۷ Gelendzhik - ۷, Russia.
Hans KUNZ - Director of CRS An der Muehle ۵, D-۲۶۵۴۸ Norderney. Germany.

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

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