Public Works and Water Management will not narrow the Boontjes fairway, located in the Wadden Sea between the Afsluitdijk and Harlingen. This decision is based on an extensive simulator study by the knowledge institute MARIN in Wageningen.
The report investigated whether the fairway could be safely narrowed from the current 100 m to 80 m. The final advice is to keep the fairway no narrower than the current width of 100 m. This allows large ships to pass each other safely along the entire route.
Dredging Efforts
Since the fairway was deepened by 1 m in 2012, dredging efforts have significantly increased. To reduce the impact of dredging on the natural values of the Wadden Sea, the Wadden Association and Harlingen port companies proposed to narrow the fairway by 20 m. However, this can only be done if the safety of shipping is not compromised.
Simulator
Therefore, we conducted a simulator study to assess the impact of narrowing on shipping safety. The input for the simulator study, which took place in April 2025, is based on discussions with various stakeholders, including lock keepers, crews of Public Works and Water Management patrol vessels, the dredging contractor, representatives of inland shipping and recreational navigation, pilots, and the Harlingen harbor service. Additionally, we provided data and knowledge.
Ships
A realistic traffic image was created for use in the simulator. Subsequently, virtual passages took place in Wageningen between representative ships in this fairway. Testing was conducted under the most common wind and current conditions.
Ultimately, 90 runs were performed over 5 days with 2 ships each, operated by experienced skippers. One heading north, the other south. After each run, they provided an evaluation.
Safety
Analysis shows that in 40% of the runs, the distances between passing ships are smaller than desired for shipping safety. The desired distance from the bank is also not consistently achieved (in 67% of the runs relative to the green buoys and in 27% relative to the red buoys).
Particularly around the bends, there is insufficient space for safe passage in an 80 m fairway, the study concludes. A narrowed fairway leaves no room for mistakes and/or misjudgments, concludes MARIN.
Narrowing is off the table
Public Works and Water Management has thoroughly studied the report and concludes that from a nautical safety perspective, the narrowing of Boontjes cannot proceed.
Project leader Jan Maarten Bakker of Public Works and Water Management: ‘We have invested a lot of energy in this research, and it is unfortunate that this option is off the table. But safety for shipping is, of course, the most important condition. Therefore, we will keep the fairway at its current, safe width. Ultimately, this is also important for nature.’
Integral Package
The research on the narrowing of the fairway is part of an integral package of measures that has been developed with the Wadden Association and Harlingen port companies. In addition to the narrowing, this includes less intervention depth and extensive monitoring. These measures are already being implemented and will continue. An evaluation will take place in 2027.