Nearshore Sediment Transport: Estimates From Detailed Measurements of the Nearshore Velocity Field

A very wide variety of conceptual models has been used to explain the movement of sediment in the nearshore region. While there is general agreement that the incident waves are primarily responsible for the mobilisation of sediment, many processes have been proposed as the transport agents, for example, wave drift velocities, wave assymetry, longshore and rip currents,undertow, the downslope component of gravity. As it is currently difficult to make reliable point measurements of sediment transport, many of these ideas can not be tested directly. However, in many cases, detailed measurements of the velocity field in the water can be used to examineat least the relative importance of these possible processes. The situation is complicated by the lack ofaccepted formulae for sediment transport. The result isthat the velocity measurements are also being used to examine the ‘reasonability’ of the various formulations.