Sediment transport in a tidal lagoon subject to varying winds evaluated with a coupled current-wave model

Bolanos-Sanchez, R., Riethmuller, R., Gayer, G. and Amos, C.L. (2005) Sediment transport in a tidal lagoon subject to varying winds evaluated with a coupled current-wave model. Journal of Coastal Research, 21 (2), e11-e26. (doi:10.2112/03-0048.1).

Abstract

The sensitivity of estimated suspended sediment transport rates was studied by applying existing current-wave fields within a coupled numerical model using the Bagnold and the Soulsby-van Rijn formulae. The study area was the Sylt-Rømø bight, an enclosed back barrier tidal basin located in the North Sea. The bight has an area of some 400 km2 in which sand flats prevail. This work provides numerical estimates of sediment transport rates and shear velocities throughout the Sylt-Rømø tidal basin. Water levels, vertically-averaged two-dimensional current velocities and wave spectra were used as input from validated numerical model calculations. Four days covering a full storm period in April 1997 were selected for the calculations of total bed shear velocities and sediment transport rates. The simulation shows that during moderate wave conditions sediment transport mainly takes place in the tidal channels. However, with high wave energy present, sediment transport becomes more important in shallow areas. The general distribution of shear velocities and suspended sediment concentrations over the basin suggests a large erosion and resuspension of sediment in shallow areas by wave action which may not be so evident in the sediment transport rates because of the low current velocities. This suggests that storms will continue to erode shallow areas, thus increasing the tidal prism and probably the tidal currents which will result in the continuing export of sediment.

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