Sea locks are a barrier between sea water and fresher inland water, allowing for control of inland water levels. They help maintain navigability for vessels, ensuring the connection of hinterland ports to the global shipping network. At the same time, they ensure the continued availability of drinking water, fresh water for agriculture and industry, and contribute to ecological stability by regulating water quality. However, the locking operations needed for vessel passings lead to salt intrusion and thus a reduction in the water quality of the inland waters. With climate change, longer periods of drought and an increase in sea water levels are expected, which increases the salt intrusion. And the growth of the global vessel industry means larger locks are needed to ensure navigability of the increasing vessel sizes, which increases the salt intrusion even more. We observe that measures taken by governments to reduce salt intrusion around locks require insight into both shipping impacts and salt exchange effects. Currently there seem no methods available to quantify how operational measures to reduce salt intrusion around locks impact both the shipping performance and salt levels behind the lock. This thesis investigates how we can overcome this gap in literature.

A first step is to identify how vessels pass shipping locks. We identify the important events that make up the entire lock passage procedure of a ship. Specifically we distinguish: approach, doors open, sailing in, doors closing, levelling, doors opening, sailing out and doors closing again. Next, we identify how the hydrodynamic processes that occur during the locking process influence salt intrusion. The most impactful hydrodynamic processes that occur are taking place between doors opening and closing, and during levelling.

Next we investigate what models are available to simulate both the shipping events and the salt exchange events. While there are several modelling concepts out there, we conclude that for the challenge at hand it is most suitable to use the mesoscopic agent-based traffic simulation model OpenTNSim to simulate vessel passages through locks. We couple this with the semi-empirical salt exchange model called the Zeesluisformulering. The main reason to choose this combination is that a discrete event agent based nautical traffic model captures exactly those events that drive the salt exchange estimates of the Zeesluisformulering. By combining both methods we get a new method that allows us to quantify how salt intrusion mitigation measures affect shipping performance and salt levels intrusion through the lock.

To determine how well the proposed combination of models works in practice we apply it to a real world case. For this thesis we select as our case location the Sea Lock IJmuiden, which at this point is the largest sea lock in the world. The lock complex in IJmuiden is suitable as a case, in February and March of 2023 salt intrusion measurements have been taken by Deltares and Rijkswaterstaat. During this period we also know what ships passed the locks, based on records taken by maritime students of the Amsterdam University of Applied Sciences. Based on these data sources we can test if the combination of models is capable of reproducing the observed behaviour...