We hindcast a 110 year period (1860–1970) of morphodynamic behavior of the Western Scheldt estuary by means of a 2‐D, high‐resolution, process‐based model and compare results to a historically unique bathymetric data set. Initially, the model skill decreases for a few decades. Against common perception, the model skill increases after that to become excellent after 110 years. We attribute this to the self‐organization of the morphological system which is reproduced correctly by the numerical model. On time scales exceeding decades, the interaction between the major tidal forcing and the confinement of the estuary overrules other uncertainties. Both measured and modeled bathymetries reflect a trend of decreasing energy dissipation, less morphodynamic activity, and thus a more stable morphology over time, albeit that the estuarine adaptation time is long (approximately centuries). Process‐based models applied in confined environments and under constant forcing conditions may perform well especially on long (greater than decades) time scales.

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Due to the construction of two cross-shore groynes near Waarde in the Western Scheldt estuary, the Netherlands, morphological changes in the area have occurred. A mud flat has developed between the groynes and at the tip of the groynes scour has occurred which has contributed to channel migration. Both the sand and mud fraction have contributed to this change. In this paper a process-based morphological model is presented that can reproduce most morphological changes thanks to the fact that both fractions are taken into account, as well as the interaction

Understanding trends in estuarine sediment fluxes is of great interest to sustainable estuarine management addressing anthropogenic interferences and climate change. The long‐term sediment budget of the Western Scheldt estuary, Netherlands, is investigated by a detailed analysis of a unique and long‐term bathymetric data set and data of a three‐dimensional subsurface model (‘GeoTop’). Different sediment types show contrasting transport behaviour. The Western Scheldt narrowed and deepened, while the estuary exported sand (1.5 to 2.5 million m3 per year) and imported mud (0.5 to 1.5 million m3 per year) over the 1860 to 1955 period. The eroded sand originated from the channels in the seaward part of the estuary and was dispersed in all directions. A significant amount of mud permanently deposited in the side branches, which were also gradually reclaimed. These results suggest that sediment characteristics potentially play a crucial role in deriving long‐term sediment budgets and morphodynamic behaviour of estuarine environments. Future morphodynamic sand–mud model studies may reproduce and further explain the underlying transport processes of the current study.