The Delta Works


Studies conducted in 1937 by Rijkswaterstaat (Department of Public Works), showed that safety in many parts of the Netherlands could not be guaranteed at times of storms and high sea levels. In the densely populated areas near the river mouths of the Rhine, the Meuse, and the Schelde, it proved very difficult to build new dikes or strengthen the original ones. The first solution was to close all the river mouths: the Western Schelde, the Eastern Schelde, the Haringvliet, and the Brouwershavense Gat. This proposal was christened 'the Deltaplan'. In 1950, the first river mouths of the Brieles' Gat and the Botlek were closed. The Brielse Maas became a freshwater basin. This not only made the area safer, but it also provided Voorne with a freshwater supply. The plan was to build the remaining dams in the following decades. Unfortunately though, the infamous flood of 1953 prevented this from happening. Nearly two thousand people died and more than 150,000 hectares of land were flooded. People soon became aware that something had to be done, and very, very quickly.

Twenty days after the flood of 1953, the Delta commission was inaugurated. The commission would give advice about the execution of the Deltaplan, that would, in the long run, increase the safety of the Delta area. Although safety was the number one priority, the seaways De Nieuwe Waterweg and the Western Schelde would have to stay open, because of the economic importance of the ports of Rotterdam and Antwerp. In order to be able to build dams in the rivers' mouths, some auxiliary dams would first have to be built in the Zandkreek, the Krammer, the Grevelingen, and the Volkerak. These dams were known as 'compartment dams', since they would divide the large area of water into multiple compartments. In 1959, the Delta Law was passed, in order to organise the construction of the dams. The building of the 'Delta Works' was such an enormous project, that it was sometimes referred to as the 'eighth wonder of the world' - and not without good reason.


The first works

Aerial view of the Stormsurgebarrier
By 1958 the first Deltawork was already operational. It was the storm barrier in the river Hollandse Ijssel. This barrier (not a dam) was of great importance because it protected the densely populated western part of the Netherlands (known as 'the Randstad') against future flooding. Three years later, in 1961, two more mouths were closed: the Veerse Gat and the Zandkreek. The water between these dams soon became fresh and is now known as the Veerse Meer (Lake of Veere).

Haringvliet sluices and Brouwers dam

An enormous array of sluices was built in the mouth of the Haringvliet in order to drain off excess water from the river Rhine. The sluices are able to be opened during very cold winters, to prevent the tide from freezeing. This could be

Overview of the southern part of the Haringvliet sluices
Haringvliet sluices
necessary to prevent the freezing of the large Dutch rivers. It was therefore, only in emergency situations, that salt water from the North Sea would be allowed to enter the freshwater Haringvliet. After the construction of the Haringvliet dam, the Haringvliet gradually became fresh. By 1971, the seventeen sixty-metres-wide sluices were fully operational. The Brouwers dam, south of the Haringvliet dam, was finished almost a year later.

The Eastern Schelde

Storm Surge Barrier in action!
According to the original plans, the Eastern Schelde would be closed, just like the other river mouths. The water enclosed behind the dam would therefore become fresh, exactly like the water in the Haringvliet and the Lake of Veere. There was some unexpected resistance against the construction of a closed dam, because people were concerned that the unique salt water environment of the Eastern Schelde would cease to exist. Specifically, not only the environment, but also the fishing industry would suffer from a dam. In 1976, the Dutch government agreed to an alternative plan: instead of building a closed dam, an open barrier would be built, containing a number of sluices that would only be closed during heavy storms and
Water flows back into the North-Sea
Storm Surge Barrier Oosterschelde
high water levels. The unique freshwater environment and the favourable fishery conditions would be maintained. Sixty-two openings, each forty metres wide, would be installed to allow as much salt water through as possible. It was supposed to maintain the tidal movement. The Eastern Schelde storm surge barrier turned out to be one of the biggest structures of the world. The costs of an 'open dam' were considerable higher than the costs of a ordinary closed dam: 2.5 billion euros were needed to complete the barrier. On October 4th, 1986, the Dutch Queen Beatrix officially opened the Eastern Schelde storm surge barrier.

Significance of the Delta Works

Stormsurge Barrier Oosterschelde, with the island Neeltje Jans.
Stormsurge Barrier Oosterschelde
Besides shortening the total length of the dikes by 700 kilometres, the Delta Works had many other advantages. Firstly, the agricultural freshwater supply was improved. Because the border between freshwater and saltwater was moved further west, less freshwater was required to balance the freshwater-saltwater division. The excess water could be transported to the north of the Netherlands, in the direction of the Ijsselmeer (Ijssel lake), where extra freshwater was welcomed to improve the water conditions.

Secondly, the complete water balance of the Delta area was improved. Thanks to the construction of the major and auxiliary dams, the streams in this area were able to be manipulated more easily. Different types of sluices made it possible to allow fresh water in, or polluted or excess water out.

Thirdly, the construction of the Delta Works encouraged traffic between the many islands and peninsulas. Large parts of the province of Zeeland had literally been isolated for centuries. The building of the Zeeland Bridge together with a tunnel under the Westerscheldetunnel (2003), also helped increase mobility.

Fourthly, the inland waterways shipping was supported by the Delta Works. In 1976, Belgium and the Netherlands signed a contract that would regulate the shipping between the ports of Antwerp and Rotterdam. Obviously, this agreement had to be taken into account when building the Delta Works.

Lastly, the Delta Works have influenced new developments in the areas of nature and recreation. Understandably, a number of nature reserves were irreparably damaged, but as compensation, new nature reserves have emerged at different sites. Nowadays, dry shores are sometimes used as recreational areas. Whether or not nature has benefited from the Delta Works will remain an unsolved debate. However, there is no doubt over the need for durable water management, in which safety, prosperity, and nature are taken into account.

Other developments

In addition to the construction of new dams and barriers, at several places, existing dams had to be heightened. This was especially the fact in the western parts of the islands (Walcheren, Schouwen, Goerree) and along the waterway of Rotterdam and the Western Schelde. The dikes needed reinforcement because they were not directly protected by the large works. It is a common misconception that the Delta Works were only built to

replace dikes. In most of the cases, building a deltawork was much quicker, and cheaper than reinforcing existing dikes. Since the building and strengthening of dikes are time consuming and expensive, another deltawork was built to the west of Maassluis at the end of the 20th century. The movable barrier, called the 'Maeslant Barrier', can close off the New Waterway when water levels are threatening the dikes in the environment. Due to the recent climate change and the rise in sea level, high water levels are more likely to occur near the coasts of Zeeland and Holland. The number of people that live in the polders, several metres below sea level, has actually increased since the flood of 1953. The general consensus among scientists is that the reinforcement of dikes and the construction of dams and barriers is in no way the final siege in the battle against the sea.