Potential dynamics of non-tidal sea bed in remote foreshore under waves and currents

Abstract

The paper presents results of considerations on possibility of bottom sandy sediment transport in the south Baltic remote foreshore under waves and currents. The analysis is based on theoretical modelling of nearbed motion of water and sand in conditions defined by the long-term wave-wind climate. The wave and wind data were collected near Lubiatowo (Poland). The study site represents the area of hydrodynamics and lithodynamics typical of the south Baltic coast built of fine sands. The wind velocities and directions were measured at the Coastal Research Station (CRS) in Lubiatowo while the wave data were collected near CRS Lubiatowo, 1–2 Nm from the shoreline, at the depth of 15–20 m. Theoretical studies comprise nearbed wave-induced oscillatory velocities, wind-induced currents and wave-current interactions. The flow velocities constitute the input for determination of the bed shear stresses. The computational results, expressed in terms of the dimensionless shear stresses (values of Shields parameter), imply a potential (possibility) of intensive nearbed sand transport under extreme wave-wind conditions. The analysis shows that the sea bed lithodynamics under respective rare conditions can yield significant short-term bottom level changes in the long-term scale.