The Deltaworks have been largely built as a consequence of the disastrous floods of 1953. Over 1800 people lost their lives and 150.000 ha of land was flooded. The building of the Deltaworks had already started before these floods, but the disastrous events of 1953 really accelerated the execution of the plans.

The Deltaworks consist of very extensive sea defense measures. The most famous are the big dams closing the tidal inlets in Zeeland, the south-western part of The Netherlands, of which the Eastern Scheldt barrier is the best known. This barrier has movable components, which make sure the unique ecology of this estuary was not damaged by closing it from the sea. To be able to build these large dams a series of smaller auxiliary dams was build in the tidal inlets. These dams are known as compartment dams. The Deltaworks shortened the total length of the Dutch sea defenses by almost 800 kilometres.

Because of their economic importance for the ports of Rotterdam and Antwerp, two of the tidal inlets in Zeeland had to remain open, the New Waterway and the Western Schelde. In the New Waterway the Maeslant barrier was built, a storm surge barrier with movable components that can be closed in case of an emergency, but doesn’t hinder shipping under normal circumstances.

Besides building these new dams and storm surge barriers old dikes in this part of the Netherlands were being strengthened as part of the Deltaworks.

The significance of the Deltaworks

Besides shortening the total length of the dikes by almost 800 kilometres, the Deltaworks 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 Deltaworks 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 Westerschelde, also helped increase mobility.

Fourthly, the shipping on inland waterways as improved by the Deltaworks. 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 Deltaworks.

Lastly, the Deltaworks 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 Deltaworks 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.

The Deltaworks consist of:

• Hollandse IJssel storm barrier
• The Three Islands Plan
• The Oosterschelde storm surge barrier
• Brouwers Dam
• Volkerak Dam
• Haringvliet Dam
• Grevelingen Dam
• Compartment Dams
• Maeslant barrier
• Hartel barrier
• Related projects