The dikes, before the Delta works Dikes were used to build out of clay, on the seaside the main part of the slopes were covered with a stone layer; those stones were being transported to the dike by the transportation means available at the time of construction. Natural stone arrived from the Belgium region of Lesse, from the region of Doornik and from Vilvoorde. While years later, when basalt (from Germany) and granite was brought (even from Poland and Portugal). Shortly after the Second World War concrete blocks were introduced in dike construction methods. They rapidly became available in different forms and sizes. The parts of the slope above the water level in case of storm were covered with grass.

The Delta dikes

For the much bigger delta dikes there was not enough clay and basalt available. That’s why the current dikes are built out of a sandy core covered with a clay layer. The basalt blocks from the seaside-dikes that were still usable are now complemented with “more modern” materials to reinforce the dikes till greater heights. Directly after the disaster asphalt was placed on the revetments of the slopes of the new dikes so that the workers were able to work faster. This revetment is waterproof, so that the powerful waves can’t reach the sandy core of the dike anymore.

There is also a disadvantage. In case of extreme rapid decrease of outer water levels, the groundwater in the dikes can’t keep up with that speed; therefore the water may pile up inside the dikes creating overpressure. Shortly after building the ‘De Ruyter Boulevard’ of Vlissingen, A strong eastern wind hit the boulevard, this caused the water level to decrease extremely fast. The overpressure created there caused the asphalt to crack.

Constructing dikes, work of men

construction of the Dutch ‘Zoudelandse zeedijk’ in 1958 horses were used to do tamp the clay soil. On the tamped clay soil basalt rock (columnar rocks with multiple corners) had to be placed by hand, which was a tough and difficult job.

Concrete blocks

A significant part of the basalt was replaced or complemented by concrete blocks after the disaster. The fact that all of them were of the same size and height and that they were therefore much easier to handle combined with that fact that the construction process was mechanized made the whole construction process a lot faster. The use of concrete blocks only was not enough because they didn’t have the height needed for the construction of the dikes. A more modern material is the concrete “basalt block” designed to come in a standard package of columnar rocks. The package consists out of a fixed number of (equally high) concrete basalt blocks of different shapes made to fit together. The edge of one standard package also fits together perfectly with the edge of the next package. Placing the concrete basalt rocks is much easier, but even with all the available instruments it still had to be done by hand. Just recently this can also be done on large scale by machinery.

Shortly after the disaster large numbers of workers filled the screen. They went living close to their work or searched a boarding house in one of the village near the construction site. Another part of the workers even lived in barracks at the construction sites. Nowadays people sometimes travel on a daily base through the whole country to get to their work.

Construction of dikes, mechanization

As said, mechanization took part of the construction process of the dikes and replaced a large part of the workers. Draglines with booms were replaced by hydraulic cranes, the real mean machines! They dig out clay and sand, load the trucks, place clay layers, tamp them with their tracks and place the stone revetments in their place.