What is a pile dike?
A pile dike is a dike whose seaward face is clad with a closely spaced wall of timber piles. That pile wall absorbed the wave impact and protected the earthen dike body behind it from scouring.
How it was built
The construction was simple in principle but labour-intensive:
- Heavy pine or oak piles were driven side by side into the toe of the outer slope.
- Behind them lay a packing of seaweed, reed or fascines, topped up with clay, acting as a filter and wave damper.
- Horizontal walings and cross-bracing held the piles in place.
- The heads stood above mean water level so the wave broke before reaching the dike.
Along the Zuiderzee, Wadden and Zeeland coasts this was the usual way to defend a dike for centuries. Timber was plentiful, and repairs after a storm could be made by local workmen.
The end: the shipworm
From 1730 onwards it emerged that the shipworm (Teredo navalis), a boring mollusc, had eaten the timber piles hollow from the inside. Piles that looked sound from outside were shells. The cladding of a large stretch of coast had to be replaced.
The answer was stone revetment: a slope covering of natural stone — later basalt columns — on a bed of fascines and rubble. More expensive to build, but immune to borers and far more durable. The shift from timber to stone is one of the great turning points in Dutch hydraulic engineering history.
What remains
Complete pile dikes no longer exist. Remains and reconstructions can be seen at a few points along the former Zuiderzee, and old rows of piles still turn up regularly during dike reinforcement works. The principle itself lives on in modern breakwaters and in timber sheet piling along canals.
Related terms
- Sheet piling
- Dike
- Driven pile
- Pile plague
- Fascine
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