Modelling response of the Dutch Wadden Sea to relative sea level rise

The Wadden Sea contains the world largest coherent tidal flats and spans nearly 500 km along the northern coasts of the Netherlands and the North Sea coasts of Germany and Denmark. It is connected to the North Sea by a series of tidal inlets, and characterized by a wide variety of channels, sand and mud flats, gullies and salt marshes. The morphological development of the Wadden Sea tidal inlet systems has been influenced by human interferences and sea level rise (SLR). In the future it is expected that the influence of accelerating sea level rise due to climate change will become relatively more important. Subsidence of seabed due to e.g. gas and salt extraction contributes to additional relative sea-level rise. Predicting the future development of the Wadden Sea under the influence of SLR is important for the management of the Dutch coastal system for two reasons. First, SLR causes an increase in sediment transport from the North Sea to the Wadden Sea and induces coastal erosion outside the tidal inlets. The morphological development of the Wadden Sea under the influence of SLR thus influences the amount of sand nourishment required to maintain the coastline and the coastal foundation. Second, the ecologically valuable tidal flats in the Waden Sea will be influenced by SLR. If SLR is too fast the system may drown, i.e., disappearance of the intertidal flats over the longer term. The future morphological developments of the six main tidal inlet systems in the Dutch Wadden Sea have been studied for various SLR scenarios based on ASMITA model simulations. The ASMITA model was developed to simulate the long-term large-scale morphological developments of tidal inlet systems. However, the used models were set up around the turn of the century, and there are many questions remaining to be answered concerning the response of the Wadden Sea to accelerating sea level rise. This contribution will present the ongoing work on the development as well as the application of morphodynamic models to predict the long-term morphological development of the tidal inlet systems in the Dutch Wadden Sea under influence of relative sea level rise.