Dutch expertise sheds new light on the risks facing the world's deltas
At Waterproof 2026, earth scientist Philip Minderhoud opened his keynote with an image of a church steeple rising from the sea. What followed was a 15-minute presentation demonstrating how Dutch expertise is helping to uncover one of the world's most overlooked climate risks: the combination of land subsidence and sea-level rise.
Minderhoud is an associate professor at Wageningen University & Research and an advisor at Deltares. Through research on Coastal-Deltaic Land Subsidence and Relative Sea-Level Rise, he works on understanding how sinking land and rising seas together increase risks for vulnerable delta regions worldwide.
What a drowning delta looks like
The audience at the Fokker Terminal in The Hague had barely settled when Minderhoud shared a photograph on the screen. It was a church steeple. Surrounding it was open water as far as the drone could capture. This was not a flood, but the permanent new reality of a village in the Philippines. "This is the people attending the last mass," he said, "before they abandoned their entire village."
His message at Waterproof 2026 was that climate adaptation efforts often focus on what is visible: rising sea levels and flooding. But an equally important process is happening below the surface.
That invisible crisis is land subsidence, driven largely by groundwater extraction. When water is pumped from deep aquifers, the clay layers above slowly compress and reorient – an irreversible process. Groundwater, Minderhoud explained, does not just carry water. It carries the elevation of the land itself. Overextract it and you pay with altitude.
Subsidence up to 20 cm per year
In the Mekong Delta, subsidence rates have more than doubled in fifteen years. In the Pampanga Delta north of Manila – where Minderhoud conducted a field survey in September 2024 – the ground is sinking by up to 20 centimetres per year.
He showed what that looks like on the ground: schools with flooded classrooms that open and close with the tides, roads raised by more than a metre, special tricycles built taller to navigate flooded streets, relocation sites that are already partially submerged and rice fields that have turned into open water.
77–132 million more people at risk
The scale of the problem may be significantly larger than current assessments suggest.
More than 90% of coastal hazard assessments use satellite elevation data referenced to a global geoid model that, in tropical regions, can significantly underestimate actual sea levels. In parts of Southeast Asia, the difference can be up to a metre.
A paper co-authored by Seeger and Minderhoud in Nature (March 2026) found that this systematic error means between 77 and 132 million more people may be exposed to the impacts of one metre of relative sea-level rise than current projections indicate.
"If sea level in reality is higher for your particular island or coastal city than was previously assumed," he said, "the impacts will happen sooner than projected."
The responsibility of water professionals
Minderhoud concluded that the water sector often spends most of its effort adapting to visible impacts, while the most effective interventions may lie in addressing the drivers beneath the surface: reducing groundwater extraction, protecting aquifers and improving understanding of subsurface processes.
He closed with a slide that underlined the responsibility of water professionals worldwide:
"A failed pilot for us may mean losing their homes for them."
Research by Wageningen University & Research and Deltares combines field measurements, satellite observations and numerical modelling to improve coastal risk assessments around the world. The findings are increasingly being used by governments and development banks to design adaptation strategies that address both sea-level rise and land subsidence.
As climate pressures intensify in delta regions worldwide, Dutch expertise in groundwater management, subsidence monitoring and delta planning is helping decision-makers better understand and respond to these complex challenges.
Learn more about sustainable groundwater management in IGRAC's long-read article.
This article is based on a piece originally published on the website of Partners for Water
