For some years now Royal Haskoning has been involved in protecting artificial islands for the coast of Dubai in the Middle East. These islands—‘Palm Island’ and ‘The World’ (an archipelago of around three hundred islands)—are being raised with sand and have to be protected against severe waves during storms. To achieve this, Royal Haskoning designed an artificial reef 25 km long. This reef is built of sand and rocks and most of it is underwater. It keeps out a great deal of the effect of the waves.
With the experience gained in Dubai, the engineers at Royal Haskoning are wondering if the concept of a reef might be a viable means of protecting the Dutch coast.
An underwater reef or reefs as used in Dubai, built at certain locations in the North Sea, could offer sufficient protection against the onslaught of the waves during the notorious westerly storms. These reefs have the effect of breaking up the heavy waves and reducing them to normal proportions, and they also prevent the coastal strip from getting ever narrower. The normal use of the coast—for recreation, living and working—can be maintained, while any coastal expansion can go ahead undisturbed.
Three alternatives
1.
Defend the coast between the Hoek van Holland and Den Helder with a reef one to two metres underwater a short distance out to sea. Think of the reefs as a string of pearls parallel to the coast with small and large to very large gaps between them. The line of sea reefs could, for instance, be installed relatively close to the coast, say a half to one kilometre out to sea, to transform the so-called weak links along the coast of North and South Holland into strong links.

2.
An underwater barrier at a distance of around five kilometres. This gives the opportunity to plan coastal development in the protected zone between the reefs and the coast on a modest local scale.

3.
A ribbon of reefs at around fifteen kilometres. This would have the effect of actually creating a large protected inland sea. There would still be tidal and wave effects in this area, but during storms the peaks would be flattened. This alternative would make the coast between the Hoek van Holland and Den Helder effectively maintenance free and offers tremendous opportunities for long term coastal development and possibly even island development in the protected coastal zone.
Building the reef out of natural materials such as sand and rock would create an ecologically sound sea-floor barrier. This barrier could easily be adapted to future developments.
Consideration could also be given to installing foundations for offshore wind turbines on the reefs. They would also provide excellent landmarks, identifying the locations of the reefs for shipping.

Before any decision could be made on large-scale implementation, there would have to be more detailed research into the risk of erosion of the coast to the North of the protected areas. The possible effect of the so-called silt river and inshore residual flow along the Dutch coast would also have to be investigated.

It is relatively simple to start a pilot project because of the flexibility and independence of the reef concept. In view of the current social discussion about the (future) safety of the coast, Royal Haskoning is urging a further study of the practical feasibility and cost aspects of installing North Sea reefs, all the more because safety and the opportunity for sustainable coastal development would unarguably benefit.

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Royal Haskoning is an international and multidisciplinary firm of consultants, architects and engineers. Our advisory services cover the broad spectrum that encompasses the sustainable interaction between people and their environment in regard to spatial development, infrastructure & transport, architecture & building, mechanical & electrical services, environment, water, coastal & rivers and maritime. We advise public and private sector organisations all over the world using our experience going back over almost 125 years and the skills of our 2700 consultants.

For more information please contact:
Maartje Verweij; +31 (0)24-3284972; m.verweij@royalhaskoning.com

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