More than a quarter of the Netherlands sits below sea level. The fact that you can keep your feet dry here is no coincidence. Over 3,500 kilometres of flood defences keep the sea and rivers at bay. The Delta Works, the Maeslant Barrier, the Afsluitdijk: these are engineering feats the rest of the world envies.
And the work continues. Across the country, dikes are being strengthened and raised, designed to withstand conditions through to 2100. The Netherlands knows how to keep water out. But what if we are preparing for the wrong scenario?
Built for a warmer world
The Delta Programme — the national plan that protects the Netherlands against flooding — assumes a warming climate. More rain in winter, higher river discharges and rising sea levels. Several scenarios have been calculated, ranging from ‘slightly warmer’ to ‘extreme warming’.
So far, so logical. “But there is a scenario these calculations do not account for,” says Suzanne Hulscher, Professor of Water Systems at the University of Twente. Her message is clear: the dikes we are building today are designed for a climate that may look very different thirty years from now.
Why the Gulf Stream could shut down
The Gulf Stream is the warm ocean current that makes Amsterdam considerably milder than Montreal, even though both cities sit on the same latitude. Thanks to that current, the Netherlands is a country of mild winters and temperate summers rather than permafrost and polar bears.
The Gulf Stream is part of a much larger system: a kind of conveyor belt in the ocean. Warm, salty water flows from the tropics northward. Around Greenland it cools, becomes heavier, sinks to the deep ocean and slowly flows back south. Scientists call this the AMOC (Atlantic Meridional Overturning Circulation). Think of it as Europe’s central heating.
That heating system is failing. As the Greenland ice sheet melts, seawater becomes fresher and lighter, which means it sinks less effectively. The engine of the conveyor belt is faltering. Climate scientists worldwide expect the AMOC could shut down entirely around 2060. Perhaps ten years earlier, perhaps ten years later.
Ice dams and frozen rivers
The Netherlands sits at the endpoint of Europe’s major rivers. The Rhine and the Meuse converge here before flowing into the sea. That makes us particularly vulnerable. Our dikes are not designed for what may be coming.
During prolonged, severe frost, something can happen that the Netherlands has not experienced for a very long time: ice dams. It starts with floating ice drifting downstream. At narrow points, that ice gets stuck and piles up into a dam. The water behind it has nowhere to go. It rises and pushes against dikes that were never designed to withstand that pressure. The ice itself also expands, damaging dike walls from the inside. This used to be a recurring problem in the Netherlands.
Then there is the economic impact. Inland shipping, which is essential for freight transport across Europe, comes to a complete standstill when rivers freeze. No raw materials, no fuel shipments, no container traffic. The economic damage would be enormous.
What can we do?
Fortunately, there is something we can do about it. The Netherlands has a head start: few countries in the world have as much experience with water management as we do. Suzanne argues for action on three fronts simultaneously. First: recalculate dike reinforcements with the AMOC scenario included. Current calculations assume a warmer, wetter climate. They need to be supplemented with the possibility of extreme cold, ice formation and highly variable river flows..
Then we need to redesign our rivers. We need to prevent ice dams from building up and blocking the flow. We need to keep the current strong in the navigation channel so it does not freeze. And we need what is necessary regardless: not just draining water, but also retaining it. How urgently this is needed became clear in July 2021 in Valkenburg: extreme rainfall turned the Geul into a raging river within hours, flooding streets and houses up to the first floor.
No dike breach, but an enormous amount of rainfall with nowhere to go. Since then, thinking about rivers has shifted: more meanders and more room. “We are now much more focused on creating space around the river, so the water can flow through when it needs to and be retained when discharge is low,” says Suzanne.
The Elfstedentocht is coming back
If it comes to that, the collapse of the AMOC will have one unexpected upside: the Elfstedentocht — the legendary 200-kilometre ice skating race across eleven Frisian cities — could be held again. According to Suzanne, perhaps as early as 2060. But only if we make sure our dikes, homes and rivers are ready for the world that comes with it. Because an Elfstedentocht is only fun if you have a warm house to come home to.
