Contrasting behaviour of sand and mud in a long-term sediment budget of the Western Scheldt estuary

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 m(3) per year) and imported mud (0.5 to 1.5 million m(3) 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.

Automated summary

This study investigated the long-term sediment budget of the Western Scheldt estuary in the Netherlands and found that sediment characteristics play a crucial role in the estuarine environment's long-term sediment budget and morphodynamic behavior.