5 Scenarios to keep the Netherlands dry
The rise in sea levels will have significant consequences for the Netherlands. This century, sea levels are expected to rise by 0.5 to 1.2 meters, with a worst-case scenario of up to 2.5 meters. Furthermore, the sea level will continue to rise, potentially reaching 5 meters by 2200. How can we keep the Netherlands dry if the water rises to such levels?
With the current dikes, we will not manage. A 0.4-meter rise in sea level already increases the likelihood of flooding in some areas by ten times. Once the sea level rises by 0.65 meters, it will be necessary to continuously pump water out of the dikes. To keep the Netherlands safe with dikes, they would need to be raised to twice the height of the sea level rise. A dike must also be able to withstand high waves during a storm. However, building such high dikes would require them to be much wider. There is little space for this in many areas, as houses and businesses are already there. But if we do nothing, 60% of the country will flood.
So, how can we keep the Netherlands dry? To investigate this, the government launched the national Sea Level Rise Knowledge Programme in 2019. This research project is part of the Delta Programme, which aims to keep the Netherlands safe until 2050 and beyond. The government, research institutions, and companies are collaborating on various ideas to make this possible.
One of the key tools for the research are the four future scenarios developed by the research institute Deltares. These scenarios explore different ways of managing sea level rise in the Netherlands. The focus is not only on preventing flooding, but also on the availability of drinking water, how effectively we can cope with waterlogging and drought, and the impact of our measures on nature.
1: The Seaward scenario
The Seaward scenario is the most technological approach. In this scenario, we create a long new island (or a series of connected islands) off the coast of the Netherlands, stretching from Cadzand to Den Helder or even to Terschelling. This new coastline would be higher than the land and serve as the first line of defense against the North Sea.
The Seaward scenario offers several advantages. For example, there would be no need to create space on our densely populated land. The current coastline would even provide more room for housing and businesses. Additionally, a large lake would be created to temporarily store excess water in case of heavy rain or full rivers.
However, the scenario also has drawbacks. For instance, it remains uncertain whether we can actually build such an island. We would need to source enormous amounts of sand – over 100 times more than for the second Maasvlakte – and require massive pumps to drain all the river water out.
There are also the interests of the economy and nature to consider. We want to ensure that our ports remain accessible to ships. Additionally, nature along our coast needs saltwater to survive. We could leave spaces between the islands, but this would make the defense much less effective. A solid coastline with locks could be a solution for ships, but not for nature. The rare tidal ecosystems with seals, birds, and unique plants would disappear. And this is not only harmful to biodiversity. Without the ebb and flow of the tide, the sea would no longer deposit sand on the coast. This would lead to 'sand hunger,' similar to what we are already experiencing in the Eastern Scheldt. If we do nothing, the sand will be spread across the seabed, and the coastline will slowly erode.
The scenario also raises the question of what will happen to the countries around us if we create a new coastline. Belgium and Germany would then face stronger currents against their dikes. Therefore, we will need to collaborate internationally.
Finally, this scenario is extremely expensive. Not only would the construction cost billions, but maintenance would also require significant funds. And that is a risk. Because if history has taught us anything, it is that floods usually occur when maintenance is neglected. Just think of the North Sea Flood disaster. It had been clear for decades that the dikes in Zeeland and South Holland were in poor condition, but the funds were always needed elsewhere. Until things went wrong.
2: The Protect Open scenario
The Protect Open scenario is one of the two 'Protect' scenarios. These two variants are the closest to the current approach. We protect the land with dikes along the coastline and allow the rivers to flow controlled into the sea. If we continue with the way we are currently protecting ourselves from the water, this is likely the path we will follow.
In the Protect Open scenario, we raise the dikes along the entire coastline and along the rivers. The Netherlands will become even more of a low-lying country surrounded by higher-flowing water. This approach doesn't require new technologies or extreme investments, although strengthening all the dikes will still be quite expensive. The nature along the coast remains largely intact, and the ports stay accessible. The Maeslantkering will need to close more frequently, but the Nieuwe Waterweg will remain open.
However, there are also drawbacks. The stronger dikes will require more space, meaning roads and buildings will need to make way. With a 2-meter rise in sea level, the dikes will need to be 0.5 to 2 meters higher and 5 to 40 meters wider. Additionally, the rise in sea level will push the ebb and flow much further inland, bringing saltwater to farmland that cannot tolerate it. We will either need to grow different crops or find large sources of freshwater. At the same time, we will have to work even harder to pump river water and groundwater from our low-lying polders out to the sea.
Finally, there is the question of whether the Protect Open scenario will be sustainable until the end of the century. With a 1 to 1.5-meter rise in sea level, the risk of flooding will increase sharply. More closures will still be necessary, such as those of the Nieuwe Waterweg. Ultimately, this could lead to scenario 3: Protect Closed.
"Which scenario is the best choice for the Netherlands?"
3: The Protect Closed scenario
The Protect Closed scenario is the second 'Protect' scenario and is similar to the current approach. This scenario differs from Protect Open in that it involves closing off the sea arms and rivers of the Netherlands with dams. The entire country would be permanently separated from the sea, and river water would be pumped into the North Sea using large pumping stations. Protect Closed can withstand more sea level rise than Protect Open, but it also presents greater challenges.
We close off the Nieuwe Waterweg and replace the Maeslantkering with a dam and lock complex. The water that continues to flow from the rivers must be pumped away or diverted via the IJsselmeer or through the Grevelingen and/or Haringvliet. In this scenario, we probably won’t need to make large-scale changes to land use behind the dikes, but salinization cannot be completely avoided.
The major technical challenge in this scenario is the pumping capacity. We would need to pump 10,000 cubic meters (10 million liters) of water per second from the Rhine and the Maas. To achieve this, we would require a pumping system 6 to 10 kilometers wide. Even if we use the entire Haringvlietdam and the closed-off Nieuwe Waterweg for this purpose, we would only be halfway there.
Increasing space will also be needed for the dikes and to store the river water that we cannot pump out all at once. Roads and buildings will have to make way, and the cost will rise. Finally, closing off the waterways will harm the nature in the sea arms of Zeeland. Seals, coastal birds, and special plant species in the Eastern Scheldt and Western Scheldt will disappear.
4: The Moving With scenario
In the Moving With scenario, the focus is on making space for the water. In this scenario, we do not protect our current land at all costs, but instead try to adapt more flexibly to the arrival of water.
In the Moving With scenario, we adapt to a water-filled world. We accept that floods will occur more frequently and ensure we are well-prepared for them. We build dikes to block the greatest threats, construct floating buildings for when the water rises, and raise roads on piles. We elevate land in key areas, while in others, we allow it to flood. Keeping peat bogs wet, for example, prevents the soil from sinking further and reduces CO2 emissions. We grow crops that are more resistant to saltwater and provide ample space for nature.
The most extreme version of Moving with means that the Dutch people will have to relocate from vulnerable areas. The cities in the Randstad would need to become 'floating cities,' or we could move economic activities to the higher-lying eastern part of the Netherlands. How much sea level rise the rest of the country can withstand depends on how quickly the natural elevation of the land occurs. The ebb and flow of the tides deposit sand and silt, allowing the land to rise by a few centimeters per year. However, the amount of sand and silt deposited is not the same everywhere.
Bonus Scenario 5: Nature-based Solutions
In 2019, the research institute Deltares developed four scenarios for the future of the Netherlands. However, in 2024, a fifth scenario was introduced: Nature-based Solutions. The first four scenarios were primarily focused on safety and the availability of drinking water, seeking technical solutions to these challenges. Nature-based Solutions, on the other hand, places natural solutions at the core, ensuring the same level of safety without harming plants and animals.
Nature-based Solutions aims to use natural processes in a smart way. For example, tidal movements can deposit sand and silt, allowing the land to naturally rise. This is already happening up to Tiel. As the sea level rises, this deposition will extend further, all the way to the German border. This is a very cost-effective way to raise the land, and higher land means lower dikes and less salinization. When we close off a sea arm with a dam, we disrupt these processes. In fact, the water behind the dam evenly distributes sand and silt over the seabed, causing the coastline to erode.
Along the North Sea coast, Nature-based Solutions can also offer other measures. Plants along the coast, for instance, can break waves, reducing the need for high dikes. Or, we could establish a ‘swap polder,’ an area enclosed by dikes that is naturally raised over time. After several years, this polder would be high enough to be used for recreation, nature, or agriculture.
Natural solutions do require more space than technical solutions. This space can partly be taken from the sea, but room must also be made behind the current dikes. Additionally, further research is needed to determine whether natural land elevation can keep up with rising sea levels.
Making choices now
Which scenario is the best choice for the Netherlands? It depends on what you consider most important. It is crucial, however, to start thinking about the direction we want to take, as each scenario will take decades to develop and implement. The decisions we make now will also affect what options remain available in the future. For example, when the Maeslantkering or the Eastern Scheldt storm surge barrier needs to be replaced, should we opt for a new open or closed variant? This choice will have implications for all other decisions in the river areas, the southwestern delta, and the Lake IJssel region.
It’s not just about decisions regarding water management. The construction of new homes, developments in agriculture, and the establishment of wind farms or solar fields also impact how much space we will have for water protection in the future. Ideally, we want to keep all options open for as long as possible, but we cannot continue to reserve space indefinitely.
We will start with measures that are included in multiple scenarios or that keep the possibility open for additional actions. For example, in all scenarios, it is crucial to create more space for excess river water and to manage its discharge. Similarly, re-wetting peat meadow areas to prevent soil subsidence and natural land elevation through sand and silt deposition are measures that are useful in every scenario.
We will not follow a straight path towards our goal but will proceed in a more exploratory manner, experimenting with various measures. The outcome will not align 100% with any one scenario but will be a mix of ideas, implemented in different ways across different areas. In this way, we will keep the Netherlands dry for centuries to come.
