Wave-induced currents and sediment transport on gravel and mixed beaches
During the last few years the interest on the behaviour of both gravel and mixed beaches has increased because of the interest in soft coastal engineering measures for combating erosion. In contrast to gravel beaches, little research has been devoted to the sediment transport of beaches containing a mixture of both sand and gravel sediment (Mason and Coates, 2001). Thus, because of the limited understanding surrounding these beaches, mixed sand and gravel coastlines have a lot of research potential for both coastal resource management and scientific reasons. In recognition of this, a series of 3-dimensional physical model tests has been undertaken in order to examine the behaviour of gravel and mixed beaches more closely. The 3-D physical model tests were carried out in the 3-D wave basin located at Franzius-Institute (Marienwerder) of University of Hannover, at a nominal scale of 1:1. During the study, measurements of beach profiles and of cross-shore and long-shore current data were taken, generated by oblique wave attack, along gravel and mixed beaches with a uniform slope and a trench. New formulae for predicting wave breaking depth index, breaking depth and height, undertow velocity, long-shore current velocity and step and berm elevation have been proposed. A new parametric profile model has been developed in order to predict the beach profile changes of gravel and mixed beaches with a uniform slope and a trench due to sediment transport. The results of the new parametric profile model and of the refined parametric model SHINGLE have been validated against field and experimental data. The results of this validation were encouraging for the refined model, showing better accuracy than the SHINGLE model and showing that it has the potential to be a valuable tool in the design and management of gravel and mixed beaches.