'One way of tackling the problem would be to get waves to break at sea while they are still some distance from the coast.'

Royal Haskoning has been involved in protecting islands built using reclaimed material in locations such as Dubai in the Middle East. Complexes of dredged islands such as Palm Island and The World are being built with sand reclaimed by dredgers but need to be protected against severe waves during storms. To achieve this, Royal Haskoning has designed artificial reefs, some as much as 25km in length.

Reflecting on the experience it has gained in Dubai, Royal Haskoning pondered whether the concept of an offshore 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 westerly storms. These reefs have the effect of breaking up heavy waves and reducing them to normal proportions, and they also prevent the coastal zone 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.

Royal Haskoning's engineers have examined three alternatives:

. Defending the coast between the Hoek van Holland and Den Helder with a reef 1 to 2m under water a short distance out to sea. The line of reefs could be installed relatively close to the coast, say 0.5km to 1km out to sea, to transform the so-called 'weak links' along the northern and southern coasts of the Netherlands.

. The second option is for an underwater barrier at a distance of around 5km offshore. This gives the opportunity to plan coastal development in the protected zone between the reefs and the coast on a modest local scale.

. The third concept is for a ribbon of reefs at around 15km, which would have the effect of 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 offer tremendous opportunities for long term coastal development and, possibly, the development of islands in the protected coastal zone.

As Royal Haskoning noted, building the reef out of natural materials such as sand and rock would create an ecologically sound seafloor barrier which could easily be adapted to future developments.

Consideration could also be given to installing foundations for offshore wind turbines, which would also provide excellent landmarks, identifying the locations of the reefs for shipping, although the company noted that before any decision could be made on implementing such a plan, there would have to be more detailed research into the risk of erosion of the coast to the North of the protected areas and on other possible side effects.