Tidal effects on cross-shore sediment transport on a shingle beach

Abstract

This paper presents a model study of the sediment transport processes of a shingle beach under the combined action of waves and tides. Parallel experiments were carried out with a constant water depth corresponding to the high water level of the tidal experiments, thus allowing a direct comparison between the two cases. It was found that the presence of the tide affected the beach behaviour differently depending on the wave climate. Under storm conditions, a rolling bar was clearly seen moving below the Mean Water Level (MWL) with both the flood and ebb tides. Under swell conditions on the flood, sediment was eroded once a critical depth had been reached but was moved onshore in the uprush to form the berm. The presence of the tide was shown to increase the size of the berm in a summer profile, and push the offshore bar further seaward in the winter profiles. The overall beach slope did not change when subjected to the wave attack without the tide but altered significantly under the combined action of the wave and the tide.