Dramatic drop in dredging boosts Wadden Sea nature, but shipping faces challenges
Residents and businesses along the Wadden Sea coast may notice fewer disruptions as dredging in the Boontjes shipping channel plummeted by 95% last year. While this benefits marine life, cargo ships now face stricter sailing conditions, potentially affecting trade and transport schedules.
| Key Fact | Details |
|---|---|
| Location | Boontjes shipping channel (Harlingen to Kornwerderzand) |
| Dredging reduction | 95% decrease in 2025 (8,000 m³ vs. 175,000 m³ in 2024) |
| New maintenance depth | -3.30 m NAP (previously -3.80 m NAP) |
| Research partners | Rijkswaterstaat, Wageningen University, Waddenvereniging, Harlingen Port Authority, Province of Fryslân |
| Impact on shipping | Deep-draft ships must sail at high tide or reduce cargo |
| Ecological focus | Monitoring benthic life (cockles, worms, crabs) and exotic species |
| Next steps | Results will inform the New Water Programme (2028–2032) |
Rijkswaterstaat manages the Netherlands' main waterways, including the Wadden Sea, balancing navigation safety with ecological preservation. This research aligns with their mandate to reduce human impact on marine ecosystems while maintaining vital shipping routes.
Read the full translated article below
The Boontjes shipping channel sees 95% reduction in dredging work: research into nature restoration underway
Published on: April 2, 2026, at 11:23 AM
In the Boontjes shipping channel between Harlingen and Kornwerderzand, dredging work has decreased by 95% over the past year. In 2025, Rijkswaterstaat removed only around 8,000 m³ of sediment, compared to over 175,000 m³ the previous year. This reduction follows the decision to shallow the maintenance depth from -3.80 to -3.30 m NAP as of January 1, 2025.
This measure aims to reduce disruption to nature while also impacting shipping. Over the coming years, it will become clear what the effects are on benthic life.
A morning aboard the monitoring vessel YE42
To investigate this, a team from Wageningen University & Research is conducting measurements this week aboard the YE42 Anne Elisabeth, a former coaster now serving as a monitoring vessel. As the ship departs from Harlingen harbor, a hailstorm passes overhead, and the winches creak in the wind.
At 20 fixed locations in the Boontjes, the team lowers a bottom scraper—a metal frame that drags about 100 m across the seabed. The material brought up is sieved on deck. Among the sand and silt, mainly common cockles, Baltic tellins, and small crabs appear. Occasionally, exotic species such as the American razor clam are found. Any fish are immediately returned to the water.
‘We measure at exactly the same spots every year,’ says researcher Douwe van den Ende. ‘The Wadden Sea is constantly changing. Only with multiple years of data can you determine whether the seabed is recovering.’
In addition to the scraper measurements, the team uses a box corer at around 45 measurement points—a robust metal frame pressed into the seabed. This brings up an intact sediment sample of about 30 cm. This sample is also sieved. The box corer provides insight into smaller species living in the seabed, such as worms.
Initial insights from the baseline measurement
The 2024 baseline measurement shows that dredged areas have significantly less variation and lower biomass than reference areas where no intervention occurs. In the reference areas, more species—and particularly far more individuals per square meter—are present. The Kimstergat dispersal site, where dredged sludge is deposited, shows a different species composition, including more amphipods.
The measurements from 2025 and 2026 will reveal whether the new approach leads to the recovery of benthic life and reduced disruption from dredging.
Impact on shipping
The shallower maintenance depth also affects commercial shipping. An earlier option to narrow the channel was scrapped due to navigational safety concerns. While the shallowing can be safely implemented, it does require adjustments.
Deep-draft cargo ships now more often navigate the Boontjes around high tide. During neap tides, when high water levels are lower, ships must depart with less cargo. Thus, reduced dredging does come with demands for shipping.
Collaboration in the Wadden Sea area
The research is part of a broader collaboration between Rijkswaterstaat, the Waddenvereniging (Wadden Association), the Harlingen Port Authority, and the Province of Fryslân (Friesland). Together, they seek a balance between accessibility and ecological value in the Wadden Sea area. The results from 2025 and 2026 will inform the New Water Programme (NWP 2028–2032).
Return to Harlingen
By mid-afternoon, the YE42 sets course back to Harlingen. A ship from the brown fleet slowly approaches as we pass by.
On deck, the crew rinses the equipment and prepares everything for transport to the laboratory. In between, they discuss what supplies need to be restocked for the next day of research. Today’s samples add to the growing dataset. It will be several years before it becomes clear whether the Boontjes ecologically recovers and whether the dramatic reduction in dredging work proves sustainable.