Everything about Afsluitdijk totally explained
The
Afsluitdijk (
English: Closure Dike,
Frisian: Ofslútdyk) is a major
dike in the
Netherlands, constructed between
1927 and
1933 and running from
Den Oever on
Wieringen in
North Holland province, to the village of
Zurich (mun.
Wûnseradiel) in
Friesland province, over a length of 32
km (20
miles) and a width of 90
m, at an initial height of 7.25 m above
sea-level.
It is a fundamental part of the larger
Zuiderzee Works, damming off the
Zuiderzee, a salt water inlet of the
North Sea and turning it into the fresh water lake of the
IJsselmeer.
Previous experiences had demonstrated that
till (boulder clay), rather than just sand or clay, was the best primary material for a structure like the
Afsluitdijk, with the added benefit that till was in plentiful supply in the area; it could be retrieved in large quantities by simply
dredging it from the bottom of the Zuiderzee. Work started at four points: on both sides of the mainland and on two specially made construction-islands (
Kornwerderzand and Breezand) along the line of the future dike.
From these points the dike slowly grew by ships depositing till into the open sea in two parallel lines. Sand was then poured in between the two dams 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.
Construction progressed better than expected; at three points along the line of the dike there were deeper underwater trenches where the tidal current was much stronger than elsewhere. These had been considered to be major obstacles to completing the dike, but all of them proved to be relatively straightforward. On
May 28,
1932, two years earlier than initially thought, the Zuiderzee ceased to be, as the last tidal trench of the
Vlieter was closed by a final bucket of till. The IJsselmeer was born, even though it was still salty at the time.
The dike itself however wasn't finished yet as it still needed to be brought up to its required height and a road linking Friesland and North Holland (the current
A7/
E22 motorway) also remained to be built. It wouldn't be until
September 25,
1933, that the Afsluitdijk was officially opened, with a monument designed by architect
Dudok marking the spot where the dike had been closed. The amount of material used is estimated at 23 million m³ of sand and 13.5 million m³ of till and over the years an average of around four to five thousand workers were involved with the construction every day, relieving some of the unemployment following the
Great Depression.
Beside the dam itself there was also the necessary construction of two complexes of shipping
locks and discharge
sluices at both ends of the dike. The complex at Den Oever includes the
Stevin lock (named after
Hendric Stevin, a son of
mathematician and
engineer Simon Stevin) and three series of five sluices for discharging the IJsselmeer into the
Wadden Sea; the other complex at Kornwerderzand is composed of the
Lorentz locks (named after
Hendrik Lorentz, the famous
physicist, who personally did the calculations of the tides that were crucial to the construction of the afsluitdijk) and two series of five sluices, making a total of 25 discharge sluices. Periodically discharging the lake is necessary since it's continually fed by rivers and streams (most notably the
IJssel river that gives its name to the lake) and
polders draining their water into the IJsselmeer.
During the period 12-13 May 1940, it was the site of the
Battle at the Afsluitdijk.
Further Information
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