Long-term process-based morphological modeling of the Marsdiep Tidal Basin

The equilibrium condition in tidal basins, especially in the Dutch Wadden Sea, a multi-basin tidal system, has been the subject of numerous studies in recent decades. This concept is very important when the tidal basin imports sediments from the adjacent coastline and its ebb-tidal delta. In the Dutch Wadden Sea, the construction of the Afsluitdijk in 1932 has affected the behavior of tidal basins, especially the Marsdiep, to a large extent and disturbed its equilibrium condition. Today, 76 years after the construction of the Afsluitdijk, the Marsdiep has not reached a new equilibrium condition and it continues to import large volumes of sand every year. In this study a process-based model based on shallow water equations is used to Simulate the morphological changes of the Western Wadden Sea for a duration of more than 2000 yr. The main forcing included in the simulations is tidal forcing and simulations with different initial conditions of the model are carried out. The main parameters of the Marsdiep tidal basin are calculated and compared with empirical equilibrium relations suggested in the literature. It is shown that such a process-based model can simulate the morphological evolution of tidal basins like the Marsdiep and can model a stable (equilibrium) condition in these basins. This stable condition is, however, strongly dependent on the initial conditions of the model as well as the forcing conditions. This paper also looks at the effect of different initial conditions on the channel and shoal pattern formation. In addition, some simulations are carried out with initial real bathymetry and the migration of the boundaries of tidal basins in the Western Dutch Wadden Sea is analyzed. The hypothesis that the basins are expanding towards the east, especially in the case of the Marsdiep, is also tested in these simulations. (C) 2008 Elsevier B.V. All rights reserved.