Haringvliet dam

Haringvlietdam (1956-1970)

The construction of the 4.5 kilometer long Haringvlietdam between Goeree-Overflakkee and Voorne-Putten starts in 1956. To close off the northern part of the Haringvliet, the same technique is used as for the construction of the Grevelingendam.

Large concrete blocks are dumped from the gondolas into the water by means of a cable car system, until a framework of concrete is established. This requires more than 100,000 concrete blocks of 2500 kilos each. For the southern section, rainbowing enough sand to create a dike is sufficient.

The Haringvlietdam has two main purposes. First of all, the dam must protect the land and water lying behind it from storm floods. Secondly, the dam must dispose of water from the rivers the Rhine and the Maas into the North Sea. That is why the dam is not completely solid, but with sluices built in.  A lock is built for the shipping industry.

Seventeen openings

The sluices have seventeen openings. If the water levels in the vicinity of Rotterdam threaten to become too high, the sluices can spew a lot of river water out into the sea. The sliders in the openings of the sluices are 56 meters long and 6 meters high each. Two of these sliders will be placed in each opening: one on the North Sea side and one on the Haringvliet side.

Before the Haringvliet is closed off, it is a large nature reserve. On the Scheelhoek – a small island in the Haringvliet – the largest breeding colony of avocets could be found for many years. In the reeds along the banks there are tens of thousands of wild geese in winter. Due to the construction of the Haringvlietdam, the Haringvliet becomes a lake.

Land that normally disappears under water during high tide is now permanently above water and is used by farmers as agricultural land. Many geese therefore lose their habitat and plants that depend on sea water also die. Crabs and shrimps do not survive the change from salt to brackish either. The European flounder and the European smelt disappear, perch and roach take their place.

Haringvlietdam
Haringvlietdam

Tunnels

In order to spare nature as much as possible, special tunnels are created in a number of openings of the sluices so that fish – even when all the gates are closed – can swim from the Haringvliet to the North Sea and vice versa. Because migratory fish such as salmon and trout, despite these measures, continue to struggle to reach their spawning areas, in 2011 the decision is made to open the sluices slightly.

The migratory fish will be able pass through the gaps and behind the sluices a natural transition will occur between salt sea water and fresh river water. This also means, however, that the western part of the Haringvliet will become saltier. The sluices will be openend in 2018, but later than planned due to an exceptionally dry summer.

Until then, the government has been working on ways to compensate for the potential loss of a source of fresh water. A fresh water route for both Voorne-Putten and Goeree-Overflakkee is created. In order to provide customers with good drinking water on Goeree-Overflakkee and Schouwen-Duiveland, Evides Water Board gets surface water from the Haringvliet and ensures that it is purified.