A Muralt wall is a low concrete wall on the crest or outer face of a sea dike, built from horizontal concrete slabs slotted between concrete posts. The walls stand roughly a metre high and were conceived as a cheap way of raising a dike without having to widen and rebuild the whole embankment.
The construction is named after Jonkheer ir. R. R. L. de Muralt, who between 1903 and 1913 headed the technical department of the Schouwen water board in the Dutch province of Zeeland. After the storm surge of 1906 he developed the system, and in 1910 he was granted a patent on it.
Why they were built
Raising a dike the conventional way means growing the whole profile: higher and at the same time wider, with a great deal of earthmoving and land acquisition. For the Zeeland water boards of the early twentieth century that was barely affordable.
De Muralt reversed the approach. A light concrete wall on the existing crest immediately gained about a metre of water-retaining height at a fraction of the cost. Between 1906 and the 1930s some 120 kilometres of these little walls were built — roughly a third of all the sea dikes in Zeeland at the time. Locally they were nicknamed “the Great Wall of Zeeland”.
Why they disappeared again
During the North Sea flood of 1953 the construction proved inadequate. A thin wall on the crest adds height, but not the mass and the broad profile a dike needs to withstand wave attack and overtopping. Where water came over, the landward face was scoured out and dike and wall failed together.
During the dike reinforcements after 1953 most Muralt walls were therefore removed. In a few places in Zeeland and on Schouwen-Duiveland remnants still stand, now protected and maintained as cultural heritage.
How to recognise one
- Concrete posts at regular spacing, with three or four horizontal concrete slabs slotted between them
- Early twentieth-century concrete, unreinforced or lightly reinforced, often showing honeycombing and carbonation damage
- Sometimes a cast-in date or the name of the water board
- The walls rarely sit on an active flood defence today, but stand in the landscape behind the present dike
Related terms
- Dike
- Crest
- Flood defence
- Wave overtopping
- Concrete
- Carbonation
- Listed building
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