Process-based Modeling of Coastal Dune Development

A model that predicts sediment transport due to wind action can be valuable addition to hydrodynamic models to describe the long-term interaction between land and water. This thesis presents the application of an aeolian transport model [Sauermann et al., 2001, Kroy et al., 2002] as a tool for the evolution of coastal nourishments and dunes. The model was originally developed to describe important features and dynamics of typical desert dunes and was modified during this research to apply to sandy beaches and coastal nourishments. Large parts of the densely populated areas in the Netherlands are located just behind the dunes. The hinterland safety in the Netherlands is guaranteed by making periodical safety assessments and keeping the 1990 coastline. In order to maintain this position, sand that is lost due to the erosive action of wind and waves has to be replaced artificially. To optimize long-term coastal management, large effort is made in the development of models to accurately predict coastal erosion and morphological behavior of nourishments. For this purpose process-based models like Delft3D can be used to asses the long-term development of nourishments. Although this model is widely used to simulate morphodynamic behavior of coastlines, processes related to the behavior of the dry beach and dunes are not included in this model. Modeling the influence of wind blown transport could improve predictions with respect to the sediment budget of the coastal zone. The main objective of this thesis is to produce a numerical simulation of aeolian transport applied to the sand engine. The existing DUNE model of Sauerman (2001) will be used to investigate the influence of morphological shaping by wind. This study will try to investigate the driving processes in the model and adapt or extend the model application to the coastal system. A morphological analysis of the beach-dune system should therefore include the influence of aeolian transport. This need becomes more urgent when dealing with a type of 'mega' nourishment like the sand engine, because of the considerable portion of surface area above the water line. Literature on aeolian transport contains a number of empirical formulas linking the transport rate to the shear stress velocity u * , derived from the logarithmic wind profile. The most famous is derived by Bagnold (Bagnold, 1941). He assumed that the horizontal momentum of grains during saltation is transferred to the ground, dislodging new particles on impact. For this research, the existing …