The Western Scheldt mouth area has shown significant changes in morphology over the past two centuries. However, the driving mechanisms behind these changes are not known yet. In this study historical bathymetries of the mouth and the basin, the incoming tide and human interventions, were analyzed, to relate different possible driving mechanisms to morphological changes.
At first, historical bathymetrical maps were digitized and cross-sectional areas and orientations of the different channels were calculated. The most important morphological change in the mouth area was the growth of the Wielingen. This growth is caused by either a changing outflow direction from the basin, or by the preferred channel location as a result of phase differences between tidal water levels and flow velocities, and wave action. The changes in the Wielingen resulted in a decrease in channel area of the Scheur and the Deurloo and in a shift of the northern channels towards the north. The western part of the Oostgat deepened after back-barrier dams were built in the Eastern Scheldt.
At second, a historical tidal analysis was performed for ten stations along the entire North Sea. It appeared that the incoming tide is related to sea level. Over time the tide has become less flood dominant. A Delft3D model was used to study the effects of the changing tidal asymmetry on sediment transport. This resulted in an increase in sediment transport out of the basin. This did not result in sedimentation on the (proximal part of the) mouth area though.