The Delta Works are the Netherlands' largest construction projects designed to protect us from water. With five storm surge barriers, two sluice complexes, and six dams, we have largely closed off Zeeland, South Holland, and North Brabant from the sea. It was a mega-project with a long history of flooding, ignored warnings, and technological innovation.
"From the above, it follows that along our entire coast, the safety of the storm surge barriers is inadequate and that the necessary enhancement must be implemented as soon as possible." This was the harsh conclusion of the Delta Commission's final report in 1960. After the 1953 Flood Disaster, the commission was tasked with devising a plan to prevent such a catastrophe from happening again.
And the commission members wasted no time. A few weeks after the disaster, they presented their first recommendations, and within a year, Rijkswaterstaat began constructing the first project: the Hollandsche IJsselkering. This marked the beginning of the Delta Works, a revolutionary plan to keep the sea at bay. It was a technological marvel without equal worldwide. But where did the idea come from? And what do the Delta Works mean for the safety of the Netherlands?
For centuries, the Netherlands has been threatened by floods. According to historians, there have been over a hundred storm surge disasters since 1200, averaging fifteen to twenty per century. Zeeland, in particular, has frequently been the victim of these calamities. For instance, there are still 'drowned lands' in the region such as the Markiezaat of Bergen op Zoom on the Oosterschelde riverbank; the Drowned Land of Zuid-Beveland, which was flooded in 1530; and the Drowned Land of Saeftinghe on the southern bank of the Westerschelde near the Belgian border. In the seventeenth century, large parts of Goeree were lost, and after a storm surge on March 3, 1715, there was fear that the island would split in two during the next tide. A hundred years later, Zeeland experienced flooding of 130 polders during the storm surge of 1808, and it happened again in 1906.
People naturally tried their best to protect themselves against this natural disaster, but the technological capabilities were limited. They were forced to adapt to the water. For instance, the Westkapelse Zeedijk was continually moved inland to preserve the island of Walcheren.
Over time, people became better at building dikes, and in the seventeenth century, windmills were developed to drain polders. This gave people renewed confidence that they could control the water and shape the land to their will. All those open connections to the sea were dangerous. Couldn’t the risk of flooding be reduced in another way?
In 1667, the hydraulic engineer Hendrik Stevin was the first to propose a plan to close off a large body of water with a dike. To prevent floods in Amsterdam, he wanted to close off the Zuiderzee (now the IJsselmeer). Or, as he put it: "to drive out the violence and poison of the North Sea from the United Netherlands."
The idea was not yet feasible. However, with the growth of the economy and population, the desire to keep the sea at bay also increased. Two hundred years later, young engineer Cornelis Lely developed the first viable plans for the Afsluitdijk. He saw that maintaining hundreds of kilometers of dikes along the coast of the Zuiderzee would be easier and cheaper if a single dam could be constructed. Additionally, this would allow fertile clay lands to be drained for more food production.
Lely managed to get his plan onto the government’s agenda as Minister of Waterstaat, but before any action was taken, disaster struck. In 1916, a major flood occurred in the Zuiderzee area. Dikes broke at dozens of locations, and more than fifty people drowned. Only then did it become possible to gather enough funds and political will to proceed with the plans. Construction began in 1920, and in 1932, the last gap in the Afsluitdijk was closed.
Meanwhile, another man was concerned about the safety on the other side of the country. Engineer Johan van Veen, who had been working at Rijkswaterstaat since 1929, focused on the water management in southwestern Netherlands. He was a skilled researcher, developing and improving measuring instruments and working on new theories about tidal movements.
He soon discovered that the dikes in many areas of the southwestern river region were too low to withstand a severe storm. He warned of this in his reports to Rijkswaterstaat, but his superiors chose to ignore his concerns. Consequently, he wrote under the pseudonym 'Dr. Cassandra' in the professional journal De Ingenieur, named after the figure from Greek mythology cursed with prophetic visions that no one believed. Unfortunately, there always seemed to be other priorities for the political leadership.
In 1939, Van Veen’s concerns appeared to be finally taken seriously when a Storm Flood Commission was established, with him as one of the members. However, a year later, the Germans invaded the Netherlands, and there was no money for a major project to raise various dikes. Research continued, and the Storm Flood Commission continued to draw attention to the inadequate dikes, particularly along the Hollandsche IJssel. If these dikes broke, a large part of South Holland would be flooded. Consequently, the commission worked on a plan to connect several South Holland islands with dams. In 1942, Van Veen even presented a radical 'Land Reclamation Plan' to close the entire coastline from Zeeuws-Vlaanderen to Vlieland. This process was to occur naturally through sedimentation and would take up to two centuries.
But the government had other concerns. First the war, then the reconstruction of the Netherlands. Johan van Veen and the Storm Flood Commission persisted. Just two days before the Flood, their final report, De afsluitingsplannen der Tussenwateren, was published, advising the construction of dams from Voorne to Walcheren. Van Veen urgently concluded: "It is proposed to continue studies in the above-mentioned sense as soon as possible."
And then came the Flood.
"The Flood, which struck our country on February 1st, weighs heavily on all of us, you and me, and the entire nation,"
In the night of January 31 to February 1, 1953, 96 large and nearly 400 small breaches formed in the dikes, allowing seawater to flood the land. An area of 200,000 hectares was inundated, 1,836 people drowned along with 182,000 animals. 3,300 homes and farms were destroyed, and another 43,000 were damaged. An even larger flood that would have submerged South Holland was narrowly averted.
Just as with the Afsluitdijk, it seemed that a disaster was needed to set plans in motion. Delay was no longer an option, as the Flood had starkly exposed the deficiencies in the Dutch dikes. Within twenty days of that terrible February night, a Delta Committee was established to develop a plan to better protect the Netherlands against water. “The Flood, which struck our country on February 1, weighs heavily on all of us, you and me, and the entire nation,” said Minister of Transport and Water Management J. Algera at the appointment of the Delta Committee. “It fills us with deep sorrow. You will agree with me that we must, as far as possible, strive to prevent a recurrence of such a disaster.” In other words: never again.
The Delta Committee got to work under the leadership of the Director-General of Rijkswaterstaat, A.G. Maris, with Johan van Veen serving as secretary. Thanks to his years of research and the reports from the Storm Flood Committee, the Delta Committee was able to quickly come up with an initial plan: raise the Schouwse dike, which runs from Zierikzee to Brouwershaven, from 3 meters to 5 meters above sea level. Later, all dikes, dams, and dunes in the Netherlands would be raised to this 'Delta height'.
Soon after, the recommendation came to close off the Hollandse IJssel with a storm surge barrier between Krimpen and Capelle aan den IJssel. This barrier would protect one of the lowest-lying and most densely populated areas in the Netherlands. It was to be a movable barrier that would normally remain open for ships but could be closed in the event of a storm surge. Within a year of the Flood, the first shovel hit the ground.
Around the same time as the construction of the Hollandsche IJsselkering began, the Delta Committee issued a new and ambitious recommendation: “In summary, the committee believes that, for safety reasons alone, it is now desirable to proceed with the closure of the sea arms in the southwestern part of the country on as large a scale as possible.”
In other words: close off as many sea inlets as possible to keep the sea at bay. The Haringvliet, Brouwershavense Gat, Oosterschelde, and Veerse Gat would now become inland waters. This would shorten the coastline from a hundreds-of-kilometers-long, irregular line full of dikes to a more or less straight coastline of just 80 kilometers, with 25 kilometers of dams. According to the Delta Committee, this plan was cheaper and more effective than raising all the dikes, while also preventing the salinization of agricultural land and improving access to the Zeeland islands.
There was just one small problem: no country in the world had ever closed such wide and deep sea inlets before, and with a combination of fixed dams and unprecedentedly large movable storm surge barriers. In its fourth report, the Delta Committee added even more with the 'three-island plan', which proposed connecting Walcheren, Noord-Beveland, and Zuid-Beveland with dams. And whether it could all be completed ‘as soon as possible’. The Delta Committee estimated that the construction of the full Delta Works would take 25 years and cost 1.5 to 2 billion guilders, equivalent to 5.6 to 7.4 billion euros (adjusted for inflation).
"The storm surge barrier is closed. The Delta Works are completed. Zeeland is safe."
Five years after the Watersnoodramp, the government approved the plan under the Delta Act. Johan van Veen lived to see this victory just in time. On December 9, 1959, he died of a heart attack while traveling by train to yet another project: the Eemshaven in Groningen.
The real work, however, was still to begin. The Hollandsche IJsselkering was completed, and work commenced on the three-island plan. This involved closing off the Zandkreek and Veerse Gat and installing a sluice in the Zandkreekdam. Following this success came the Grevelingendam, Volkerakdam, Haringvlietdam, Brouwersdam, and the Oosterscheldekering. The latter is undoubtedly the most impressive—and expensive—piece of civil engineering in the Netherlands. The barrier was officially opened on October 4, 1986, by Queen Beatrix, who declared: “The storm surge barrier is closed. The Delta Works are complete. Zeeland is safe.”
However, this conclusion was short-lived. In 1988, it was decided to build an additional Delta Work. Due to rising sea levels, a movable dam was needed in the Nieuwe Waterweg to protect South Holland and keep the port of Rotterdam accessible. This storm surge barrier, the Maeslantkering, was completed along with the Hartelkering in 1997.
Ultimately, the Delta Works consist of five storm surge barriers, two sluice complexes, and six dams to protect the Netherlands from the North Sea. Sometimes these barriers and dams include multiple components with additional dams and sluices. When all these waterworks in Southwest Netherlands are counted separately, there are five storm surge barriers, ten sluice complexes, and seven dams.
But the significance of the Delta Works extends far beyond merely protecting the land from the dangerous sea. In the wake of the Delta Works, new agricultural landscapes, recreational beaches, nature reserves, islands, lakes, forests, and ports were created. Zeeland became more accessible, we can better manage water levels, and we have established a reserve of fresh water. It has become a remarkable environment where every detail of technology and landscape has been thoughtfully considered.
The Delta Works remain the central component of the flood protection system safeguarding the Netherlands. Yet, they are gradually aging and becoming more vulnerable, while climate change causes storm surges to intensify and sea levels to rise further. In 2018, all storm surge barriers had to be closed for the first time, and this was repeated in 2023.
At the same time, the potential impact of a flood is now even greater than in 1953. With a larger population, a flood would result in more casualties. Nearly 60 percent of our country could be inundated, including major cities and a large portion of the economic hub.
So, how do we keep the Netherlands safe in the future? What happens with 2, 3, or even 5 meters of sea level rise? The Delta Works (and the Afsluitdijk) were not designed for such extremes. Should we once again adapt to the water, as we did in the past, or should we strive to find a technological solution?
Many researchers and engineers are actively addressing these questions. They are contemplating how we can tackle the challenges posed by climate change and even improve our country in the process. This involves not just safety, but also technical possibilities, nature-inclusive solutions, the availability of fresh water, preventing salinization, accommodating shipping, and finding places to live and recreate.
Hopefully, we have learned from Cornelis Lely and Johan van Veen, and we will not need a flood to prompt timely action. Onward to Delta Works 2.0!
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