IMIS

Model outcomes show that the joint action of extreme wave and wind events causes an increase of sand volume of the mouth area in the course of time, thereby leading to smaller volume of channels (channels infill, in the order of 0.1 cm/yr) and larger volume of shoals (higher shoals, in the order of 0.1 cm/yr), particularly in the offshore part of the mouth area. These volume changes are larger with increasing number of extreme events. Moreover, when adding extreme events, the orientation of the offshore parts of channels changes as well. Increased shoal volume and channel infill with time also occurs in case of only extreme wave events, but these volume changes are much smaller than those in case that extreme wave and wind events are added to the model. The Western Scheldt estuary experiences relatively minor changes in its sand volume over time when including wave and extreme events. Results further show that a different chronology of extreme events influences the morphodynamic evolution of the mouth. However, the tendency of increased channel infill and sand gain by shoals in the mouth area with sand that is imported from the North Sea remains qualitatively the same. In case of including additional wave growth by wind, wave action during extreme wave events becomes stronger, and thus more sediment is resuspended in the water column, which is subsequently imported into the mouth area, resulting in enhanced infilling of channels and sand gain by shoals.