The thousand-year storm
At the Belgian coast on 1 February 1953, the combination of a rising spring tide and a storm depression causing southwesterly winds that later turned northwesterly led to sea levels two metres higher than normal for the time of the year.
A super-storm could one day flood large areas of Flanders – unless something is done to hold back the sea
Nearly five kilometres of sea dyke collapsed, and seawater flooded 500 hectares of polder land. According to conflicting reports, between 14 and 22 people died, the loss of livestock was huge and the economic toll considerable.
However, Flanders got off relatively lightly. The February storm was not meteorologically the worst of the year, although the duration and the amount of water involved made it the most damaging. Just up the coast in the Netherlands, 1,800 people lost their lives, and 100,000 lost their homes and possessions. A storm such as that is expected to happen about every 250 years.
Right now, the Agency for Maritime and Coastal Services is preparing for a 1,000-year-storm. “It will come one day,” says Tina Mertens, an engineer employed by the agency. “It could be next winter. And our coastline has to be able to withstand it.”
The 1,000-year storm – the so-called super-storm – would feature five-metre-high waves and the raising of the sea level by seven metres. The agency calculates that the hinterland would flood as far as Bruges and Diksmuide.
In parts of the Flemish coast, the polders – where the land is lower than sea level – extend as far as 20 kilometres inland. The area also represents various interests – agricultural, recreational and environmental – which all have to be balanced when decisions are made on the use of the land. If the current circumstances were to continue, the superstorm would cause an estimated €3 billion in damage, with as many as 4,000 casualties.
What can we do?
The Integrated Coastal Safety Plan is a series of measures guarding against the danger of a super-storm to be taken between now and 2050. The plan has been compared to the Deltaworks constructed along the Dutch coast after 1953, including the Oosterschelde barrier closing off the eastern arm of the Scheldt between Noord Beveland and Schouwen-Duiveland.
The Flemish plan will not include anything as spectacular, however, and will cost upwards of €300 million. The Oosterschelde barrier cost €2.5 billion, but then Flanders only has 67 km of coastline to protect.
The plan is based on a study that split the coastline into 255 strips, each about 300 metres wide. For each strip, a comprehensive risk analysis was made: how would this stretch of coast stand up to a super-storm?
“A good third of our coast is inadequately protected against a really heavy storm,” Mertens says. At some points, where the dyke is built-up, there is a risk of massive waves sweeping away sand and reaching the dyke itself, bringing down apartment buildings in the worst case scenario. In other parts, by the harbours of Zeebrugge, Blankenberge, Nieuwpoort and Ostend, sea-walls are relatively low and higher water could easily rush over them. It’s already a regular occurrence in winter for the sea to reach the level of the wall and even to slip over.
The Zeedijk in Wenduine is reckoned to be the single weakest spot on the entire coastline because it juts out into the sea like the prow of a ship. Locals call it the Rotonde, and every year it’s reinforced with new sand, which washes away almost as fast as it can be deposited.
The Plan evaluates the problems in each of the 255 strips and offers possible remedies. Then it’s up to the Flemish government, in cooperation with the municipalities along the coast, to decide what can and must be done. Sometimes only one option is open; other times a number of options have to be weighed according to the different interests.
Sea-wall
The ideal solution would be to build a wall the length of the coast to keep the sea out. That’s not likely to happen, however, because it wouldn’t be cost-effective. The agency stresses that one-third of the coast is inadequately protected. There are parts of the coast where raised sea walls offer a solution, but the coast municipalities are opposed, since even a one-metre wall can be enough to ruin the outlook from a house or apartment whose main selling point is its sea view.
Closing harbours
Ostend will soon see the effects of new harbour developments, with the construction of two sea dams in the approach to the harbour – the East Dam and West Dam. Essentially two long sea walls, the dams will reduce the impact of waves in the harbour and provide an easier and faster passage for ships entering and leaving Ostend.
They will also slightly re-orient the harbour in a northerly direction, almost perpendicular to the coastline. In the event of a storm, the dams would absorb much of the impact of the sea at some distance offshore.
The centre of town, however, to the east of the harbour, remains a weak spot. The first measure to tackle that problem will be a reinforcement of the dyke at the Zeeheldenplein, a monumental square facing out to sea where the town meets the docks. That work will go ahead as soon as possible, without waiting for reactions to the integrated plan.
“The question of coastal safety is extremely important, but people still have to be able to live, work and enjoy themselves,” said mobility and public works minister Hilde Crevits when she visited Ostend in October last year. “I’m pleased to note that things are working well here: besides the work on safety, there is also attention being paid to the maintenance of the heritage value of the Zeeheldenplein, and the tourist-recreation possibilities of the site are being increased.”
Harbours are a particular weak point in coastal protection, with heightening of quay walls required in Nieuwpoort, Blankenberge, Zeebrugge and the rest of Ostend.
Shoring up the beach
One way to make the dykes and dunes less vulnerable to damage from the sea is to make the beach broader. That would be accomplished, Mertens explains, by bringing in sand and raising the level of the beach. The high-water mark is then pushed further from the dykes or dunes, and the beach itself takes more of the impact of normal waves and storms.
Every year the coast receives about 500,000 cubic metres of imported sand – about 200 Olympic-sized swimming pools of the stuff – for shoring up, tackling erosion and other emergency measures. To extend beaches would require at least three times as much again. The problem with such huge amounts of sand is the source: the kind of sand needed comes from protected areas, and supplies are not infinite.
The option of extending the beach is also not popular with the coastal communes because it would attract more tourists to the beach itself, and tourists largely don’t eat and drink at the restaurants and bars lining the seafront.
Extending the sea dyke
Bringing the dyke closer to the sea is an option the tourist industry is more likely to support, since a larger sea dyke allows more room for café terraces. But the question of sea view can also arise: some dykes, such as the one at Wenduine, are currently so low they virtually serve no purpose, and if they were to be reinforced they would also need to be raised.
Protecting the dunes
The nature protection agency Natuurpunt has called for the Coastal Plan to take more account of the needs of nature in coastal areas. One important factor here is sand dunes, which not only provide natural protection against the sea but also represent an important habitat for animals, birds and plants. At some points on the Belgian coast – Oostduinkerk, Knokke and Blankenberge, for example – grass barriers have been planted to help retain dune sand.
