Salt intrusion in channels with complex geometry

Saltwater intrusion in estuaries can threaten freshwater supplies, as highlighted by recent drought periods. This thesis improves our understanding of how saltwater moves inland through estuaries, with a particular focus on the influence of harbors and dredging channel beds in the lower estuary, two factors that are highly relevant to the Rhine-Meuse estuary. Through numerical modelling, field measurements, and data analysis, the research shows that side basins such as harbors can affect salt transport through the exchange of water with the main channel and highlights the role of currents between the main channel and harbor that are driven by salinity-induced density differences. The study also demonstrates that sudden changes in channel depth caused by dredging influence how far saltwater penetrates upstream and that the abruptness of these depth transitions has a profound effect on salt intrusion. Finally, a simple prediction tool was developed that enables rapid estimation of salinity levels in estuaries, supporting day-to-day water management decisions.