• Coastlines around the world are vulnerable to rising sea levels.
  • Huge dams, blocking off areas as large as the North and Baltic Seas, could be an answer.
  • While hugely expensive on paper, the costs of inaction will be far higher.

On 14 December 1287, the dikes that held the North Sea back from the Netherlands coast broke. The resulting inundation, known as St. Lucia’s Flood, caused between 50,000 to 80,000 lives to be lost. Already specialists at building dikes prior to this disaster, the Dutch people consequently reinforced their existing dikes while improving their skills as dike-builders.

Since then, dikes have safeguarded newly created arable land while protecting the Netherlands from rising sea levels. Today, the dike network extends for more than 22,000 km, and has reduced the length of the Dutch coastline to a mere 880 km from a previous high of 2,600 km in the 16th century.

The Dutch did not build dikes purely to protect their lands from the North Sea, however; they also used the dikes as a catalyst for engineering the countryside and economy with innovations such as polder fields and the canal systems that crisscross the Netherlands.

Fast forward to the present day, and coastlines across the entire world are vulnerable to rising sea levels. Even if the pledges made in the Paris accords are met by the global community, the IPCC still predicts sea levels to rise between 30 and 60 cm. And that is probably the best-case scenario. We still don’t know the full consequences of man-made global warming, so in a worst-case-scenario the Paris Accords might not be sufficient. And if the pledges aren’t met, the sea will surely rise by a few metres globally over the next few centuries - and this is without considering the other extreme weather hazards which will become more frequent as global temperatures rise, such as storms and droughts.

Governments, therefore, should still do everything in their power to meet the Paris tarrgets, but they must also start planning infrastructure for a future of rising sea levels because our current ambitions still might not be enough. And they shouldn’t only focus solely on just how to protect our coastlines, but also on how to engineer and design economies, ecology, connectivity and urbanism as part of this.


The time has come for the development of geographical giga-projects such as the Northern European Enclosure Dam (NEED) suggested by Sjoerd Groeskamp from the Royal Netherlands Institute for Sea Research. Groeskamp suggests the building of two dams: a 475km dam between Scotland and Norway and a 160km one between England and France at a cost of €508 billion ($601 billion).

This would be the largest piece of man-made engineering on the planet, dwarfing the 33km Seamangeum Seawall in South Korea by some distance. NEED is one vision, but we need more like it – and we need to consider how such projects will tie into the future development of the regions affected, or regions created by these projects. How can they also be used to drive innovation in ecology, energy, and regional development to spur new sustainable megaregions?

With the global urban population projected to grow by 2.5 billion by 2050, we could be looking at massive relocation away from coastal cities – if we don’t think outside the box. The cost of these endeavours would most likely surpass any economic outlay ever conceived. But we do need more ideas for large scale coastal protection and redesign, along with the task-forces necessary to design and envision new urban regions and ecosystems to accompany these projects.

Similar to the NEED seawall, one might also consider a 100km dam between Northern Denmark and Sweden to protect the Baltic sea region. This project could include plans for a high-speed rail-system to even further connect the Nordic region and provide a closer link to Europe in a future where we depend less on carbon-intensive transport for short-distance travel. Similar approaches need to be considered across the world in areas such as the Lagos Delta, Bangladesh or the coasts of China to mention just a few.

Trends in absolute sea level across Europe based on satellite measurements, 1993-2019
Trends in absolute sea level across Europe based on satellite measurements, 1993-2019
Image: European Environment Agency

While the costs of these giga-projects might seem astronomical at first glance, one need only compare them to the costs of doing nothing and multiply that over the next few hundred years. As Groeskamp and his colleagues have pointed out: “Based on monetary value alone, the cost of inaction exceeds that of protection and managed retreat by a factor of between five and 10.”

If the five countries most affected by NEED were to combine their efforts and pay for the dam, it would amount to between 0.15% and 0.32% of their annual GDP over the 20 years of construction. In comparison, estimates for a sea level rise of up to 1.5m by 2100 put the costs alone for the Netherlands at between €1.6-€3.1 billion ($1.9-$3.7 billion) a year up to 2050.

Similarly, the cost of damages due to extreme weather in the US was $110 billion in damages in 2012 and $160 billion in 2005, largely caused by coastal hurricanes.

How do we get started?

This leads us to the discussion of who should spearhead the initialization of the work to protect our coasts. The obvious answer is for larger urban regions to increasingly work together in order to develop financially viable ways to mitigate the consequences of climate change.

One example is the STRING framework, which is focused on creating a green mega-region in Northern Europe as proposed by the OECD. At the moment it includes the urban regions of Oslo, Gothenburg, Malmo, Copenhagen and Hamburg. These five regions (Scandinavia on its own ranks as the 17th-largest economic region globally, with a combined GDP of $1.3 trillion) and economies alone would benefit immensely from a giga-project of this nature, and this is without including the larger cities of the Baltic Region such as Helsinki, Saint Petersburg, and the German, Baltic and Polish coastal cities. Combined, this area is one of the world's top economic regions.

Denmark also recently announced plans for the construction of 'energy islands' – hubs for offshore wind generation – in the North Sea, and it would be unwise if this plan, at least, didn’t also consider how it would integrate with a Baltic Sea dam. The key here, of course, is that Denmark is planning for a future built on renewable energy with the wind being one of these components. But a Baltic Sea dam also presents an opportunity to look even further into possibilities of designing new renewable energy sources using hydropower or building aquaculture-based farming with a view to creating a sustainable means of prospering as a planet in the future. For too long we have been creating and designing human-centred solutions, and it goes without saying that any undertaking of this size should be conducted in a wholesome approach that considers planetary resilience for the future.