CROSS-SHORE SEDIMENT TRANSPORT MECHANISMS IN THE SURFZONE ON A TIMESCALE OF MONTHS TO YEARS

Klaas T. Houwman, Gerben Ruessink

Abstract


The relevance of several cross-shore sediment transport mechanisms on a timescale of months to years was studied. Data from a large measuring campaign carried out in the outer surfzone of a barred surfzone was used to calculate sediment fluxes. The transport rates were calculated using the measured near bed velocities and sediment concentrations, and two sediment transport models. Both fluxes and the transport rates are only significant during breaking waves. The high-frequency fluxes/transports are onshore directed, the mean fluxes/transports are offshore directed, and the low frequency waves also give offshore directed fluxes/transports. Taking into account the frequency of occurrence of the conditions, the breaking wave conditions turned out to be the most important for the cross-shore sediment transport on a timescale of a year. The cross-shore sediment transport is a delicate balance between the onshore directed high frequency term and the offshore directed mean term. Therefore the smaller terms, like the low frequency term and the bedload term, may still be of importance to the net sediment transport.

Keywords


time scale; crossshore transport; sediment transport; surf zone

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