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...

Lake Bardawil is a hypersaline shallow micro-tidal double-inlet lagoon on the northern coast of the Sinai Peninsula in Egypt. The inlets, named Boughaz 1 and Boughaz 2, connect Lake Bardawil to the Mediterranean Sea. The local population relies on the fishing yields from the lagoon, however, in the current situation, the lagoon’s inlets are unstable, needing constant maintenance dredging to stay open. Additionally, due to the hypersaline situation (limiting fish attraction) and high fish catch demand, the current fishing situation is unsustainable. The Weather Makers propose a solution to the problem using dredging interventions. Enlarging the inlets of Lake Bardawil is expected to result in increased fish migration, decreased salinity in the lagoon and increased stability of the inlets. This research aims to investigate the short-term response of Lake Bardawil and specifically its inlets to the dredging interventions proposed. To investigate the response to the interventions, two numerical models are used; a hydrodynamic model in D-flow FM and a coupled morphological model using D-flow FM and D-waves. The model results are analysed in terms of the hydrodynamic tidal response, combined hydrodynamic response to tide and weather and finally the morphological response to tidal and weather effects. From the hydrodynamic model, it can be concluded that the interventions result in a larger tidal prism for the lagoon by a factor of 1.6. This is expected to result in increased fish migration and reduced salinity in the lagoon. As the tidal prism increases, so does the discharge through the inlets. The increased discharge through the inlets results in inlet velocity amplitudes that exceed the theoretical critical value for convergence to a dynamically stable inlet cross-section for both inlets. The interventions affect more than just tidal currents in Lake Bardawil. Weather effects in the lagoon are amplified by the interventions. This is demonstrated by increased interaction between the inlets in terms of net import and export of water. During winter storms, the wind-induced flow from Boughaz 1 to Boughaz 2 is greater in magnitude. The wind waves caused by these winter storms result in sediment resuspension. This results in larger sediment transport from the basin to Boughaz 2. Using the coupled model, the morphological response in both inlets can be predicted. In Boughaz 1, the present sediment-importing character is amplified. Whereas the similar summertime sediment-importing character of Boughaz 2 is reduced substantially. The sediment export of Boughaz 2 during winter is larger in the new situation. The interventions result in increased sedimentation in the dredged channel of Boughaz 1. This does not hinder the increased tidal discharge at Boughaz 1, which is the main intended function of the interventions. This means the increased sedimentation does not influence the intended functioning of the interventions in the short term. Due to the increased sedimentation in the inner dredged channel, there is no indication of increased stability in Boughaz 1. Boughaz 2 shows less morphological activity in the situation after interventions. As is the case with Boughaz 1, there is no hindrance to the functioning of the interventions during the short simulation period. There is reduced deposition of sediment in the inner flood delta region of the inlet and the updrift side of the inlet channel compared to the known unstable situation during both winter and summer simulations. This indicates improved stability for Boughaz 2. The short-term response to the interventions in the inlets of the Lake Bardawil system is as intended, the tidal prism is increased and while there is only an indication of increased stability in Boughaz 2, there are no short-term impediments to the intended primary functioning of the interventions in either of the inlets.