Field measurements of the three-dimensional current structure in the vicinity of a headland-associated linear sandbank

The complex three-dimensional tidal flow measured in the vicinity of a headland-associated linear sandbank near Cape Levillain and the Levillain Shoal (Shark Bay, Western Australia) is described. The measurements included moored instruments (current meters, ADCP), shipborne ADCP transects, and drifters. Eulerian and Lagrangian current measurements provided a detailed description of the hydrodynamics. Results showed the presence of strong currents near the headland, reversal of currents veering towards the bank during the flood and ebb, and the formation of a transient eddy around the bank at slack water. Throughout the tidal cycle, secondary currents were present at the headland, with secondary flow near the seabed directed towards the headland and surface secondary flow directed away from the headland. Near the bank, near-bed secondary flows were directed towards the centre of the bank on both flanks at both the flood and ebb phases of the tide. Based on the detailed hydrodynamic data, a conceptual model for sediment transport pathways near the sandbank is proposed. The sandbank appears to be part of a sand circulation cell where the sand circulates around the bank with exchanges between the sandbank and the headland.