Swash zone sediment transport

The coastal area is a busy area, many people live in these areas or use the coastal area for recreational purposes. The beach profile in the coastal area is continuously changing under the changing field conditions. These changes are induced by the changing sediment transports in the sea under changing field conditions. Several models have been developed to simulate and predict these changes in sediment transport and their related profile changes. However, these models fail in a region close to the shoreline, since the parameterized wave models (like Battjes Janssen, 1978) fail in this region. In this thesis a model has been developed to compute the sediment transport rates up to zero meter water depth. This Inner Surf Zone (ISZ) sediment transport model is based on the ISZ model of Aarninkhof, 2000, which models the wave height decay and the associated flow field up to zero meter water depth. The ISZ sediment transport model uses the energy approach of Bailard (1963;1966) for the sediment transport computations. According to Bailard the sediment transport is related to the work done by the fluid, the dissipated energy. The sediment transport is divided in two layers in the ISZ sediment transport model, an upper and a lower layer. In the lower layer suspended and bed load sediment transport is taken into account. In the upper layer only suspended sediment transport is computed, based on the shear stresses near the bottom. The sediment concentrations in the upper layer are assumed to decrease, when the water depth increases, resulting in a decreasing sediment transport in the upper layer. Implementation of this assumption by an empirical formula into the model works encouraging well. The model is calibrated against the tests of Koomans in the Scheldt flume (2000). The model is valid for spilling breaking and the computation area is determined by the non-linearity parameter of the waves. The non-linearity parameter depends on the wave period and so does the range of the model. Different field conditions have been investigated in this thesis. Changing transport rates for varying beach slope and sediment composition can be modelled encouragingly well by the developed ISZ sediment transport model. The ISZ sediment transport model requires adjustment when field conditions like wave height and wave period change, since the friction factor and the sediment concentrations change under changing field conditions. Based on the described changes in sediment transport in literature, under these changing field conditions, a recommendation is made how to adjust the model parameters. The friction and the bed/suspended load efficiency factors are used to represent the described changes in sediment transport under these changing field conditions.Civil Engineering and Geoscience