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Problem statement: Due to increased demand from shipping a new shipping lock has been build at the mouth of the North Sea Channel. This new shipping lock will lead to increased salt intrusion into the North Sea Canal and subsequently in the Amsterdam-Rhine Canal. To combat this additional salt intrusion, a Selective Withdrawal structure will be built that will increase the outflow of saline water from the North Sea Canal.

Problem impact: The impact of the shipping locks (including the new bigger lock) in IJmuiden, combined with the still to be built salt screen will be able to limit and manage salt intrusion.

Client: Rijkswaterstaat


Project owner: Anton de Fockert

Team members: Arnout Bijlsma, Helena Nogueira, Tom O'Mahoney, Arne van der Hout, Gosse Oldenziel & Experimental Facility Support



Period: 2016-present


Rijkswaterstaat built the world’s largest sea lock at the entrance of the North Sea Canal in IJmuiden, to allow future larger vessels to sail to the Port of Amsterdam. As a consequence, a larger volume of salt water will enter the North Sea Canal after each lockage cycle, which has adverse effects for agriculture and drinking water in the region. Rijkswaterstaat aims to remove the extra salt from the larger lock by means of selective withdrawal of salt water using the pumping station and the discharge sluices existing in IJmuiden. For this purpose, a screen with an opening at the bottom will be built at the entrance of the Binnenspuikanaal, such that mainly salt water (which is heavier than fresh water) will end up at the discharge sluices and the IJmuiden pumping station.

Earlier numerical simulations performed by Deltares (Delft3D and detailed CFD) have shown the effectivity of a selective withdrawal near IJmuiden to reduce the salt impact on the North Sea Canal. However, due to the complex nature of the flow patterns around the salt screen, characterized by highly 3D flow and flow separation around the southern bend, physical scale model tests were necessary to validate the numerical CFD model. The validation of a numerical model for this complex flow behaviour is crucial for using the numerical models to assess the effectivity of the salt screen.


Physical scale model research was performed in the Lock Facility at Deltares. In the scale model the reference design of the salt screen as created by Royal HaskoningDHV was tested at scale 1 to 40. The scale model research focused on the flow patterns around the screen in the presence of a stratified density distribution, i.e., salt water at the bottom and fresh water on top.

Advanced measurement techniques were used in this project, such as PIV and 3D PTV. Particle Image Velocimetry (PIV) is an optical technique that was used to characterize the flow through the screen by tracking small laser-illuminated particles added to the flow. Particle Tracking Velocimetry (PTV) was applied by our experts at Deltares for tracking the flow patterns in a large area upstream of the salt  screen. This was needed to investigate the amount of flow separation at the southern bend. The concept behind both techniques is that particles are transported by the flow, from which flow velocity and flow patterns can be derived.

Result and Impact

Selective withdrawal has been shown to be an effective measure to mitigate salt intrusion. The results of this research have also shown that CFD modelling is able to represent the flow patterns around the salt screen as measured in the physical scale model accurately.

Reports and Publications

  • Fockert, A. de, O'Mahoney, T.S.D., Nogueira, H.I.S. & Oldenziel, G. (2021). “Assessing the Effectiveness of the IJmuiden Salt Screen Design for Nonuniform Selective Withdrawal by Physical and Numerical Modeling”. In: Journal of Hydraulic Engineering 148(2). http://doi.org/10.1061/(ASCE)HY.1943-7900.0001958

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