The 20-mile-long (32-kilometer) Afsluitdijk (literally, “closing-off dike”), constructed from 1927 to 1932 between Wieringen (now Den Oever) and the west coast of Friesland, enabled the resourceful Dutch to turn the saltwater Zuider Zee (South Sea) into the freshwater IJsselmeer and eventually to create an entire new province, Flevoland. Like their successful responses to similar challenges before and since, it was an audacious and farsighted feat of planning, hydraulic engineering, and reclamation.
Throughout their history, the Netherlanders have fought a battle against the water. Much of their tiny country is well below average sea level, in places up to 22 feet (7 meters). The threat of inundation comes not only from the sea but also from the great river systems whose deltas dominate the geography of Holland. Over centuries, literally thousands of miles of dikes and levees have been built to win agricultural land back from the water, and having gained it, to protect it. From the seventeenth century Amsterdam merchants invested their profits in building the North Holland polders—Beemstermeer, the Purmer, the Wormer, the Wijde Wormer, and the Schermer—reclaimed through the ingenious use of the ubiquitous windmill.
In 1250 the 79-mile-long (126-kilometer) Omringdijk was built along Friesland’s west coast to protect the land from the sea, and as early as 1667 the hydraulic engineer Hendric Stevin bravely proposed to close off the North Sea and reclaim the land under the Zuider Zee. His scheme was then technologically impossible. The idea was revived in 1891 by the civil engineer and statesman Cornelis Lely. Based on research undertaken over five years, his plan was straightforward: a closing dike across the neck of the Zuider Zee would create a freshwater lake fed by the River IJssel and allow the reclamation of 555,000 acres (225,000 hectares) of polder land—in the event, 407,000 acres (165,000 hectares) were won. Despite Lely’s assurances about the feasibility of the plan, his parliamentary colleagues were unenthusiastic. But attitudes changed after the region around the Zuider Zee was disastrously flooded in 1916; moreover, World War I (in which Holland remained neutral) convinced the Dutch government that internal transportation links needed to be improved. The Zuiderzee Act was passed in 1918.
The Zuiderzeeproject commenced in 1920 with the construction of the Amsteldiepdijk, also known as the Short Afsluitdijk, between Van Ewijcksluis, North Holland, and the westernmost point of the island of Wieringen. There were some initial foundation problems and a financial calamity for the contractor, but the dike was completed in 1926. There followed the construction of the small test polder Andijk (1927) and the Wieringermeer (1927–1930).
The key element in the daring plan was the construction of the Afsluitdijk across the Waddenzee, an arm of the North Sea. The project was undertaken by a consortium of Holland’s largest dredging firms, known as N. V. Maatschappij tot Uitvoering van de Zuiderzeewerken. All the work, involving moving millions of tons of earth and rock, was carried out manually by armies of laborers working from each end of the structure. Built during the Great Depression, the Afsluitdijk was a welcome source of employment. It was completed on 28 May 1932. It was intended later to build a railroad over the broad dike, but as the volume of road traffic increased in Holland, priority was given to a four-lane motorway. The railroad was never built, although adequate space remains for it.
The closure of the Afsluitdijk enabled the eventual reclamation of three huge tracts of land formerly under the sea: the Noordoostpolder (1927–1942), East Flevoland (1950–1957), and South Flevoland (1959–1968). They were later combined to become a new province, Flevoland, with a total area of over 500 square miles (1,400 square kilometers). Its rich agricultural land supports two cities, Lelystad and Almere, although the latter is more properly a dormitory for Amsterdam. Flevoland is on average 16 feet (5 meters) below sea level. The great freshwater body south of the Afsluitdijk was renamed IJsselmeer. Its balance, carefully controlled through the use of sluices and pumps, is determined by inflow and outflow rates, rainfall and evaporation, and storage level changes. With a surface of nearly 500 square miles (131,000 hectares), it is the largest inland lake in the Netherlands. A proposal to reclaim a fifth polder, the 230-square-mile (60,300-hectare) Markerwaard, behind a 66-mile-long (106-kilometer) dike between Enkhuizen and Lelystad was not pursued, mainly because of ecological concerns.
In February 1998 the Dutch Ministry of Transport, Waterways, and Communication published the Waterkader report, setting out national water-management policies until 2006. Aiming to keep the Netherlands safe from flooding, it presents a case for reserving temporary water-storage areas—“controlled flooding”—against times of high river discharge or rainfall. The government, recognizing that raising the dikes and increasing pumping capacity cannot continue forever, has adopted the motto “Give water more space.” The document Long-Range Plan Infrastructure and Transport of October 1998 promised to invest 26 billion guilders (approximately U.S.$13 billion) in the nation’s infrastructure before 2006. Part of the money is earmarked for waterways, including links between Amsterdam and Friesland across the IJsselmeer.