Afsluitdijk

The Afsluitdijk (in French: dam of closing ) is a Digue of big size of the Netherlands, built between 1927 and 1933, connecting Den Oever on Wieringen (province of septentrional Holland) to the village of Zurich (mun. Wûnseradiel) (province of Plank). The work has a length of 32 Kilomètre S, for a width of 90 Mètre S, with a 7,25 meters height to the top of the Sea level. It is the showpiece of the Travaux of Zuiderzee, which close the Zuiderzee, an old gulf of the the North Sea, from now on a fresh water extent called IJsselmeer.

Preceding experiments had shown that the Till (glacial Argile ), better than simply of the Sable or clay, was the best material for a structure of ground such as Afsluitdijk, with the additional advantage that this matter was abundant in the surroundings. It could be easily extracted by dredging simply sea-beds Zuiderzee. Work was started in four places: on each side of the coast, and starting from two artificial islands (Kornwerderzand and Breezand) in the alignment of the future dam.

Starting from these points of construction, the dam was set up gradually by the boats bringing the till in the sea in two lines parrallèles. Sand was consequently brought between these two dams, and was covered with another layer of till when the work started to emerge. It was then reinforced by blocks of Basalte and piles of Saule inserted at the base. The dam could consequently be finished by adding other layers of sand and of clay, to be finally covered with vegetation.

Construction progressed more quickly than envisaged. In three places, pits were present, with a current of tides stronger than elsewhere. They were regarded as a major difficulty, but it appeared that this one could be easily controlled. The May 28th 1932, two years earlier than envisaged, Zuiderzee ceased existing at the time when the last passage of tide of the Vlieter was blocked by a block of till. IJsselmeer had been born, even if it were still strongly salted at that time.

The dam itself was not finished yet, since it was to still be elevated with the required height, and the road connecting Frise and septentrional Holland (current highway A7/E22) was to still be built. It was only the September 25th 1933 which Afsluitdijk was officially inaugurated, by a monument indicating the place where the dam had been closed. One estimates at 23 million m ³ the total volume of sand and 13,5 million m ³ of till used, and an average from 4 to 5.000 workers employed permanently for this work, employment for them welcome in this time of the Grande depression.

Beside the dam itself, it was necessary to build lock S to allow the passage of boats, and Vanne S at each end of the dam. The Complexe of Den Oever includes the lock Stevin and three series of five valves to evacuate the water of IJsselmeer towards the Mer of Wadden. The other complexes located at Kornwerderzand includes/understands the lock Lorentz and two series of five valves, for a total of 25 dump valves. Periodically, it is necessary to discharge the lake from the surplus of water brought by the rivers (in particular the IJssel, which gives its name to the lake) and the Polder S which evacuate their water towards IJsselmeer.

See too

Plane Delta
Interliner

Nds-nl: Ofsluutdiek

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