Barriers and dams: exporting Holland's sea defences

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The massive storm surge barrier on the mouth of Eastern Scheldt along the south-west coast of the Netherlands was officially opened 25 years ago. It is an awe-inspiring feat of modern engineering and construction: a dam some 9 kilometres in length with enormous sliding sluice gates which can be raised to make the dam watertight in the event of extremely high waters or a storm-induced surge in the North Sea. An example of Dutch sea defence know-how that has since become a major export product.

[media:image]The Eastern Scheldt storm surge barrier was built at a time when the threat of rising sea levels had yet to loom large as it does now. This particular barrier was the final part of the larger project known as the Delta Works, which the Dutch thought up and implemented to protect low-lying areas in the coastal provinces of Zeeland and South Holland following the massive and disastrous floods of 1953. Then, large parts of the country were inundated following high tides in combination with a severe storm over the North Sea in February of that year. More than 1,800 people lost their lives in the Netherlands. There was also severe flooding in England, though the death toll there was considerably smaller.

Originally, the Eastern Scheldt barrier was due to be a closed dam, closing off the sea completely. Protests by the environmental movement ultimately resulted in the inclusion of large sections which were left open to the sea but with enormous hydraulically driven gates to close them off when needed. The sliding gates have indeed been used to seal off the dam a total of 24 times in the last 25 years. Cities such as London and St Petersburg followed the Dutch example and have their own moveable barriers, while Venice is working on a similar system.

The knowledge and expertise the Dutch gained in building the Delta Works has turned out to become a successful export product – as illustrated by the Mekong Delta project in Vietnam.

Pier Vellinga, professor in climate change at Wageningen University, is an advisor on the sea defence project in Venice. The plans to build a barrier there met with a number of ecological objections at the end of the 20th century, but Professor Vellinga’s arguments regarding rising sea levels played a role in the Venetians’ eventual decision to put the plans into effect. Venice has opted for a variation on the Dutch Delta Works - its barrier has moveable gates underwater. A colossal structure like the Eastern Scheldt barrier would ‘pollute’ the horizon for this historic city.

There’s a need for similar moveable sea and water defences in various places around the world. This need exists because of the threat of rising ocean and sea levels and the threat to precious brackish-water environments. The question is can developing countries come up with the necessary billions that such projects cost? Professor Vellinga believes they will - ultimately:

“Of course, barriers like these are rather expensive, but safe harbours in coastal areas can do a lot of good for the economy. Moreover, the storm surge barrier system in the Netherlands also provides a highway that links the province of Zeeland with the port of Rotterdam. So barriers also have an economic spin-off.”

Exchange of know-how
The export of Dutch skills and experience is not entirely a matter of one-way traffic, however. There are also things which Dutch water engineers can learn from other countries. Siebe Schaap from the Netherlands Water Partnership (NWP) has, for instance, spent a considerable time working in the Indonesian capital, Jakarta: “There are some 20 million people there who needed to be protected against the water [threat]. The things learnt there are in turn applicable to the Netherlands and other places.”

The NWP is a joint project involving Dutch government agencies, researchers and the private, commercial sector, aimed at marketing Dutch know-how in the field of water management to the rest of the world. There’s also the I-Storm platform which serves as an exchange for knowledge and experience relating to sea defences.

Decide in haste, repent at leisure
Siebe Schaap says the Eastern Scheldt storm surge barrier is still one of the world’s most impressive water defence construction projects. Not only because of its sheer size, but also because the amount of research that was carried out for it. This meant that water systems, sand movements and the ecological impact were all measured and recorded in great detail. Siebe Schaap says:

“That’s the difference with, for example, the Three Gorges Dam in China. That construction was built quickly and without much forethought. That’s when you encounter major problems later on, by which time the thing has already been built. So, the skill of well-planned execution, that’s something you can learn from the Dutch.”