Estuaries are located where freshwater river flow meets ocean saltwater in an environment of channels, shoals, intertidal flats and vegetated area, like salt marshes or mangrove belts. They comprise both unique ecosystems and economic values such as navigational gateways to ports. Estuaries face significant challenges from morphological changes caused by natural and human activities such as land reclamation and dredging. In addition, rising sea levels threaten tidal flats and biodiversity. This research investigates centennial timescale morphodynamic developments in the Western Scheldt by means of a process-based model (FINEL2d). The model demonstrates good skill in hindcasting morphodynamic changes uniquely observed between 1860 and 1970. Analysis of sub-surface sediment composition and bathymetric data reveals a trend of historic sand export and mud import with the estuary narrowing and deepening over time supported by model results. Model simulations further suggest that, on a centennial timescale, morphodynamic developments evolve towards equilibrium.
This study shows that dredging and historic land reclamation have significantly altered morphodynamic evolution of the Western Scheldt estuary. It demonstrates both the significant impact of human interferences and the potential for designing sustainable management strategies to preserve a combination of vital ecosystems and economic values in the face of ongoing climate change.