September, 2018

The Delta Works in Zeeland make for an interesting comparison with a large ecosystem engineering project which I saw at the beginning of my Netherlands trip – the Afsluitdijk.

Together these two projects have been declared one of the “Seven Wonders of the Modern World” by the American Society of Civil Engineers. While the purpose of both projects is to protect low-lying land from the storm surges of the North Sea, there are major differences both in ecological effects and in engineering complexity.

The Afsluitdijk – “closing off dike” – is a 32 kilometre causeway built between 1927 and 1932 across the opening of the salt-water Zuiderzee, which then turned into the fresh-water IJsselmeer.

The Afsluitdijk spans the 32 km between North Holland and Friesland.

From the beginning the Afsluitdijk has also been used as a transportation corridor. Although a planned railway line has not been built, today the causeway is the site of an expressway as well as a bike route, connecting the provinces of North Holland and Friesland.

Looking north along the Afsluitdijk. The bicycle road is in the middle, with expressway at right.

Although I had great anticipation of biking this route, it turned out to a bit of a letdown. The highest part of the dike is right along the North Sea coastline, while the bike path and highway are at a lower level on the IJsselmeer side. This means that while riding one cannot see the North Sea. I had envisioned pedaling along with the mighty waves nipping at my heels – but the reality was not so dramatic. On the other hand the prevailing south-west wind was strong, and right on my back the whole way across.

I did get off the bike a few times and to climb over the dike and down the well-protected embankment. I was very impressed by the huge amount of careful  but low-tech work that had gone into the construction of a wall that can resist and dissipate the force of North Sea storms.

The sloping west side of the dike is armoured against the North Sea with paving stones.

The Afsluitdijk has been an undoubted success in protecting a sizeable portion of the country from storm surges – but there have been major costs, too. In particular, many towns on the coast of the former Zuiderzee had been fishing ports for centuries. Once they were cut off from the sea, an entire way of life came to an end, and ecosystems are still working towards a new balance.

Both the benefits and the costs of the Afsluitdijk were close to mind when the Dutch constructed the Delta Works at the south end of the country.

February, 1953

The North Sea Flood of 1953 was caused by a high spring tide in combination with a severe wind storm, resulting in a storm surge as high as 5.6 meters above mean sea level. Over the night of January 31–February 1, the storm caused extensive damage in England, Scotland, Belgium and the Netherlands.

The province of Zeeland took the hardest hit. One area of the country was spared, however – the lands around the Zuiderzee/IJsselmeer. The conclusion was that all the construction costs of the Afsluitdijk had been paid for in one night in February 1953. And almost immediately serious planning began for a similar level of flood protection in Zeeland.

The Afsluitdijk had been a huge project and had been discussed for hundreds of years before a workable plan was outlined and construction began. Yet providing protection for Zeeland was even more challenging.

As a group of several islands in a salt-water estuary, Zeeland has a vast area of coastline.

This estuary is the mouth of one of Europe’s great river systems, the Rhine. Any dramatic changes to that estuary would therefore also lead to manifold long-term changes in a vast watershed ecosystem. Finally, two of Europe’s largest ports – Rotterdam and Antwerp – are located in this estuary, and closing these ports was not something planners wanted to contemplate.

An overall plan for the Delta Works was rapidly set in motion in the wake of the 1953 flood. Significant parts of Zeeland were in fact sealed off from sea water. But by the 1960s and 1970s, Dutch citizens had serious qualms about irrevocably altering the entire delta.

The solution that was implemented took several different forms. Rotterdam harbour is now protected by massive movable flood gates that allow ships – and salt-water tides – through in ordinary conditions, but which can be temporarily swung into place to stop storm surges when needed.

At the south end of Zeeland, the opening to the sea was left completely open so that the port of Antwerp also remains open, and that meant dikes had to be raised and fortified.

And in the middle, a string of artificial islands, dams and floodgates stretches from island to island.

I bicycled across several of these fortifications as I followed the coastal roads from Ouddorp to Renesse on one day, and from Renesse to Middelburg the next.

The 8 kilometre section spanning the Oosterschelde (see map of Zeeland above) made for an awesome ride, helped by a stiff tail wind and brilliant sunshine.

The 62 flood gates here are grouped in three groups, and each gate can be closed within about 1 hour. By Dutch law the whole assemblage can only be closed when there is a surge of at least 3 metres above normal sea level. Since the project was completed in 1986, the gates have been closed 27 times. (However each individual gate is closed once a month for testing.)

When the Delta Works project was completed the cost was pegged at a bit more than €11 billion, with a significant portion coming from the proceeds of the rich, but now dwindling, Groningen gas field. The planners stated they expected the storm surge barrier system to last for 200 years.

But a lot has changed in the past 30 years. In 2008 the Delta Commission warned that due to climate change, the country must plan for sea level rise of 1.3 meters by 2100, and 4 metres by 2200. To fortify flood protection components to cope with these new sea levels, the commission said, the country should expect to budget €100 billion over the next 80 years.

As I biked over the Oosterschelde barrier, I was struck by how massive the fortresses appear, and also by the force of the water streaming through. I wouldn’t want to bet against the Dutch, but I also wouldn’t want to bet against the sea. I’m glad I don’t have to put down any chips.