After revisionTime-dependent measurements of flow velocities and sedim
ent concentrations were conducted in a large oscillating water tunnel.
The measurements were aimed at the flow and sediment dynamics in and
above an oscillatory boundary layer in plane bed and sheet-flow condit
ions. Two asymmetric waves and one sinusoidal wave were imposed using
quartz sand with D-50 = 0.21 mm. A new electro-resistance probe with a
large resolving power was developed for the measurement of the large
sediment concentrations in the sheet-flow layer. The measurements reve
aled a three layer transport system consisting of a pick-up/deposition
layer, an upper sheet flow layer and a suspension layer. In the asymm
etric wave cases the total net transport was directed ''onshore'' and
was mainly concentrated in the thin sheet flow layer (< 0.5 cm) at the
bed. A small net sediment flux was directed ''offshore'' in the upper
suspension layer. The measured flow velocities, sediment concentratio
ns and sediment fluxes showed a good qualitative agreement with the re
sults of a (numerical) 1DV boundary-layer flow and transport model. Al
though the model did not describe all the observed processes in the sh
eet-flow and suspension layer, the computational results showed a reas
onable agreement with measured net transport rates in a wide range of
asymmetric wave conditions.