December 14, 2011

By the zee

The Afsluitdijk

If you were born in Holland in the year 1200 and lived a really long time, you might have had the misfortune of witnessing two of the country’s greatest floods ever – the first in 1212, when nearly 50,000 people died in the Noord Holland flood, and then in 1287, when 60,000 or more people perished on December 14.

The numbers represent nearly ten percent of the entire population at the time; these were devastating events.

By then, the Dutch had given the arm of the North Sea that reached into the heart of the Low Countries its own name – it was the Zuiderzee (the Southern Sea), and most of the time it behaved like a shallow placid lake, albeit salty.

But when North Sea storms caused the Zuiderzee to flood, it both gave and took away.  People, first of all, then towns and then the land itself.  It took almost all of the island village of Griend in the 13th century, leaving only ten houses standing.  Today Griend is basically a sandbar used as a bird sanctuary.

At about the same time it gave a village on the Amstel a new oceanfront view and a harbor for Baltic traffic and the village grew to become Amsterdam.

Map by Scipius

Sometime at the end of the 19th century, the Dutch decided to master the Zuiderzee.  They planned a dam that would enclose about two thirds of it and drainage that would turn the saltwater menace into a real freshwater lake.

It would be expensive, of course, and it would take a long time and there were interest groups – like fishermen – that didnt want things to change, so the idea was kicked around for about twenty years without even getting to Parliament, until January of 1916 when another flood occurred.  It was business as usual for the Zuiderzee of course, but it turned out to be the last straw – Parliament passed a bill and they got started.

Officially called the Zuiderzeewerken, the American Society of Civil Engineers lists it as one of the Seven Wonders of the Modern World.  They went very slowly, first building a 2.5 kilometer practice dam at the narrowest point – that took four years and a lot of money.  But they learned a lot and when they got to the 32 kilometer (about 20 mi.) main course they knew what they were doing.

But if you’re thinking concrete and rebar, guess again – it turns out that the best way to keep out the North Sea is sand, clay, rocks and some willow. A material called till (boulder clay) was dredged from the bottom of the Zuiderzee itself and laid in two tracks from one side of the Zee to the other.

 Sand was then poured in between the two dikes and as it emerged above the surface was then covered by another layer of till. The nascent dike was then strengthened from land by basalt rocks and mats of willow switch at its base. The dike could then be finished off by raising it further with sand and finally clay for the surface of the dike, on which grass was planted.

It’s called the Afsluitdijk – the Enclosure Dam – and if you drive north across it, the Wadden Sea, what remains of the arm of the North Sea, is on your left and Lake IJssel  – what used to be the Zuiderzee – is on your right. The IJsselmeer is fresh water, fed by the river IJssel.  It took fifteen years (1918-1933) and in current dollars, cost about $1.5 billion.

The other wonders of the modern world, as chosen by the ASCE, btw, are the Panama Canal, the Empire State Building, the Golden Gate Bridge, the Canadian National Tower, the Itaipu Dam and the Channel Tunnel.



  1. Wowwyzoowy what man can do with sticks and stones. Great blog.


    Comment by avery — December 15, 2011 @ 7:13 am | Reply

  2. When will we stop trying to win a battle with Mother Nature?


    Comment by Carol — December 18, 2011 @ 7:28 pm | Reply

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