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Zuiderzee Works

The Zuiderzee Works (Zuiderzeewerken in Dutch) are a massive hydraulic engineering project undertaken by the Netherlands in the 20th century. Its main purposes were to offer protection from the ravages of the sea and enabling the reclamation of land in extensive polders to be used primarily for farming at first and later also housing.

Table of contents
1 Prelude
2 Zuiderzee becomes IJsselmeer
3 New land
4 Noordoostpolder
5 The Flevolands
6 The fifth polder
7 External links


In 1916 the dikes at several places along the Zuiderzee (the current IJsselmeer) broke under the stress put on them by a winter storm, and the land behind them was flooded as had often happened in the previous centuries. This particular flooding, however, would provide the decisive impetus to existing plans to tame the Zuiderzee, this shallow inlet of the North Sea protruding into the low-lying lands of the Netherlands. The concept of making the Zuiderzee more docile had first originated in the 17th century, but the ambitious solutions sought then were not possible given the technology of the time.

The second half of the 19th century saw the emergence of the first feasible plans, with the primary objectives being improved protection from the open sea and the prospect of valuable new agricultural land. One of the most ardent proponents was Cornelis Lely, an engineer by profession and later government minister, whose 1891 plan would form the basis for what were to become the Zuiderzee Works: a large dam connecting the north of North Holland with the western coast of Friesland and the creation of inititally four polders in the northwest, the northeast, southeast (later split up into two) and southwest of what would be then renamed the IJsselmeer (IJssel-lake), with two major lanes of water spared for shipping and drainage. The initial body of water effected by the project would expand over 3500 km². Opposition came primarily from fishermen along the Zuiderzee who would lose their livelihood, but also from other people living in coastal areas along the more northerly Wadden Sea, fearing higher water levels as a result of the closure, as well as those who doubted whether it was financially possible in the first place.

However, when Lely became Minister of Transport and Public Works in 1913, the government started working on official plans to enclose the Zuiderzee. The 1916 flooding combined with a continuously threatening food shortage during the First World War strongly supported the arguments of the advocates of the project and they turned out to be the final straws needed; on June 14 1918 the Zuiderzee Act was passed and the mammoth undertaking was now under way. The following points were set out as the main goals of the Act:

After the Dienst der Zuiderzeewerken (Zuiderzee Works Department), the administration responsible for overseeing the construction and initial management, was set up in May 1919, work could commence in earnest. It was decided to not start building the main dam first, but rather to test the waters with a smaller dam, the Amsteldiepdijk across the Amsteldiep separating the island of Wieringen from the North Holland mainland. Despite its limited length of just 2.5 km the dike took 4 years to build, from 1920 to 1924. It had nevertheless turned out to be a valuable learning experience which was put to use in the later projects.

Map of the Zuiderzee Works

Zuiderzee becomes IJsselmeer

A new study, commissioned after doubts had arisen over the financial feasibility of the project, recommended that work should not only continue, but should be accelerated. It was therefore decided to start the next two major projects at the same time, in 1927. The most important of these would be the main dam, the Afsluitdijk (Closure-dike), running from Den Oever on Wieringen to the village of Zurich in Friesland over a length of 32 km and a width of 90 m, at an initial height of 7.25 m above sea-level and an incline of 25%.

Previous experiences had demonstrated that till (boulder clay), rather than just sand or clay, was the best primary material for a structure like the Afsluitdijk, with the added benefit that till was in plentiful supply in the area; it could be retrieved in large quantities by simply dredging it from the bottom of the Zuiderzee. Work started at four points: on both sides of the mainland and on two specially made construction-islands (Kornwerderzand and Breezand) along the line of the future dike.

From these points the dike slowly grew by ships depositing till into the open sea in two parallel lines. Sand was then poured in between the two dams and as this emerged above the surface it was covered by another layer of till. The nascent dike was then strengthened from land by basalt rocks and mats of willow switch at its base. The dike could then be finished off by raising it further with sand and finally clay for the surface of the dike, on which grass was planted.

Construction progressed better than expected; at three points along the line of the dike there were deeper underwater trenches where the tidal current was much stronger than elsewhere. These had been considered to be major obstacles to completing the dike, but all of them proved to be relatively straightforward. On May 28 1932, two years earlier than initially thought, the Zuiderzee ceased to be as the last tidal trench of the Vlieter was closed by a final bucket of till. The IJsselmeer was born, even though it was still salty at the time.

The dike itself however wasn't finished yet as it still needed to be brought up to its required height and a road linking Friesland and North Holland also remained to be built. It wouldn't be until September 25 1933 that the Afsluitdijk was officially opened, with a monument marking the spot where the dike had been closed. The amount of material used is estimated at 23 million m of sand and 13.5 million m of till and over the years an average of around 4 to 5000 workers were involved with the construction every day, relieving some of the unemployment following the Great Depression.

Beside the dam itself there was also the necessary construction of two complexes of shipping locks and discharge sluices at both ends of the dike. The complex at Den Oever includes the Stevin lock and three series of five sluices for discharging the IJsselmeer into the Wadden Sea; the other complex at Kornwerderzand is composed of the Lorentz locks and two series of five sluices, making a total of 25 discharge sluices. Periodically discharging the lake is necessary since it is continually fed by rivers and streams (most notably the IJssel river that gives its name to the lake) and polders draining their water into the IJsselmeer.

New land

The other major project started in 1927 was the construction of the first of the five projected polders, namely the northwestern one and at 200 km² also the smallest one. It would replace the body of water south of Wieringen known as the Wieringermeer which would also become the name of the new polder. It would be the only polder reclaimed from the Zuiderzee itself (the others were reclaimed after the Afsluitdijk was finished), but it wasn't entirely the first. A small test polder of some 40 hectares was constructed in 1926/1927 near Andijk in North Holland to research the effects drainage would have on the soil of the Zuiderzee and how best to configure the new polders.

Building the encircling dike for the Wieringermeer would be a little harder than it was for the later polders, since the Wieringermeer dikes had to built without the major advantage the as yet unfinished Afsluitdijk would have for reclamation: the absence of tidal currents. As a consequence they would have to be somewhat higher. Construction started on the 18 km long dike from Den Oever on Wieringen and the new construction-island of Oude Zeug and progressed very well; the Wieringermeer was closed off from the Zuiderzee in July 1929. The next step would now be to drain all the water from the future polder.

Drainage of a polder is performed by a pumping station or mill, called a gemaal in Dutch. Two were built for the Wieringermeer, the Leemans, a diesel powered station, near Den Oever and the Lely, an electrically powered one, near Medemblik. Different ways of powering the stations is used as a fail safe mechanism; should a calamity cause any one station to lose its source of power, the other one would then still be able to keep the polder dry. The pumping mechanism itself was based on the screw pump design by American inventor A. Baldwin Wood. The stations, completed in February 1930, managed to drain the polder after six months of continuous pumping. "Drained" in this context does not mean the land was wholly dry; extensive pools of shallow water still littered the muddy landscape. To make the soil usable it needed to be further drained by a network of drainage channels. Many small ditches were dug that led to larger watercourses who in turn transported their water to the main drainage canals, dredged when the polder was still filled with water, which conducted the surplus water to the pumping stations. The resulting dehydration would cause the former seabed to sink in (at places the sinkage could be well over a metre) and once the ground had set work could start on replacing the smaller ditches with underground drainage tubes which would be used for the normal drainage of the polder.

Zuiderzee Works Dates
Project Length Start Closure Drained
Amsteldiepdijk 2.5 km June 29 1920 July 31 1924 ---
Afsluitdijk 32 km January 1927 May 23 1932 ---
Wieringermeer 18 km 1927 July 27 1929 August 31 1930
Noordoostpolder 55 km 1936 December 13 1940 September 9 1942
Eastern Flevoland 90 km Early 1950 September 13 1956 June 29 1957
Southern Flevoland 70 km Early 1959 October 25 1967 May 29 1968
Houtribdijk 28 km 1963 September 4 1975 ---
With the hydrological infrastructure in place, a beginning could be made with developing the virgin land in preparation of its later cultivation. The first plant to establish itself, though more so in the later polders than in the Wieringermeer, would be reed, sown from the air by plane onto the muddy flats while the polder was still being drained. This sturdy plant helped to evaporate the water, bring air into the soil and thereby solidifying its structure and further preventing the emergence of unwanted weeds.

After the first infrastructure was put in place the reed was burnt and replaced by rapeseed, turning the newborn polder into a yellow sea of flowers in spring. These crops were succeeded by various species of grain; in the Wieringermeer the first would be rye, but the later polders followed the order of first wheat, then barley and finally oat. This process could take several years, but once finished farmers could plant the crops they wanted and with other infrastructure such as roads and housing also in place the polder was now ready for people to live and work in.

The Wieringermeer, as the first of the envisioned five polders, served as a major testbed for ideas and techniques for the following projects. It's closest to the original concept of the new land being primarily for use as agricultural land and it has retained a strong rural character. Four villages (Slootdorp (1931), Middenmeer (1933), Wieringerwerf (1936) and Kreileroord (1957)) eventually grew up in the polder. The local administration presented a new problem at first; the area was divided among the mainland municipalities according to the boundaries used when there was still water, a configuration that wasn't always practical on the ground and one that unnecessarily split up reponsibilities over several parties. A solution was at first found in a novel form of government called an openbaar lichaam or "public body"; a complicated arrangement which incorporated both the administration in charge of the actual development and an appointed committee responsible for public governance. As the polder became more populated the demand for proper representation increased until finally on July 1 1941 the municipality of Wieringermeer was established.

Most of the hard work of the 1930s in building the Wieringermeer would come to naught as the Second World War drew to a close. The Netherlands were occupied by Nazi Germany and on April 17 1945 a vengeful German command ordered the dike of the Wieringermeer to be blown up. No-one was killed as the polder slowly submerged again, but the high water and a subsequent storm destroyed most of the infrastructure built in the previous decade. Reconstruction followed quickly; by the end of 1945 the polder was declared drained again and rebuilding the roads and bridges, houses and farms, was greatly facilitated by the experience of building them the first time.


The original 1891 plan called for the largest, southeastern polder to be built after the Wieringermeer, but it was decided in 1932 to give precedence to the smaller, and therefore considered easier, northeastern one. This would be the Noordoostpolder, meaning simply "Northeast-polder". Initial financial difficulties meant that it wasn't until 1936 that construction began. Two dikes, totaling 55 km in length, steadily grew in the IJsselmeer, one starting from Lemmer in Friesland and from the island of Urk, the other from Vollenhove in Overijssel and again Urk. The outbreak of the Second World War led to the construction of this latter dike and the necessary pumping stations to be delayed; it wasn't until December 1940 that the encircling dikes were both closed, but the pumping stations would not be ready to start draining until early 1941. The Noordoostpolder was considered to be sufficiently drained in September 1942 and the developmental process was then put in motion on the 480 km² of new land.

The task of building the Noordoostpolder was eased by the earlier experience, the now placid waters of the IJsselmeer and the mechanisation of the construction process. Machines, sometimes made specifically for the Zuiderzee Works, would increasingly be used for this and the final polders. Land usage would be much the same as in the Wieringermeer, again focusing on farming and areas with less fertile soil designated as forest land. Land in the polders was state-owned during the entire developmental process, but when this was completed after several years the various plots could be distributed among private parties. Priority was at first given to the early pioneers who had been in the polder since the start, afterwards interested farmers from all over the Netherlands were eligible for the remainder and candidates would be put through a selection process before receiving their own piece of new land.

Contained within the polder are two former islands, the glacial moraine hill of Urk and the elongated strip of peatland known as Schokland. Urk was then and is still today a fishing community and it served as a natural construction-island for both dikes as well as a base of operations for the later exploitation of the polder. Urk ceased to be an island on October 3 1939 when the dike reaching from Lemmer was closed; Schokland, an island abandoned in the 19th century now lying within the polder, had to wait until the water surrounding it had been drained away. Both islands stand out in the new land, both physically and figuratively, as the community of Urk in particular has remained an entity somewhat distinct from the "mainland", e.g. it constitutes a separate municipality from the rest of the polder which would form the proper municipality of Noordoostpolder in 1962.

At the heart of the Noordoostpolder, where the three main drainage canals intersect, is the town of Emmeloord (1943). Planned from the outset to be the first and the only major town of the polder, it serves as the local governmental and services centre. Ten smaller villages, conceived more as agricultural communities, were planned in a wide circle around Emmeloord, with the distances between them determined so as to be easily reachable by bicycle. The first settlements were Ens, Marknesse and Kraggenburg (1949), followed by Bant (1951), then Creil and Rutten (1953), and finally Espel, Tollebeek and Nagele (1956). From Emmeloord three canals take their water to three pumping stations, the Buma near Lemmer, the Smeenge at Vollenhove and finally the Vissering in Urk. The first two are electrically powered (though connected to different power-plants), the latter one has diesel-engines doing the pumping. Like all pumping stations of the Zuiderzee Works they too were named after individuals who had at some point made a significant contribution to the project.

The Flevolands

The period immediately following World War II was spent on restoring the Wieringermeerpolder and catching up with work on the Noordoostpolder, but it wasn't long before attention turned towards the next project: Eastern Flevoland (Oostelijk Flevoland), at 540 km² the largest of the new polders. In 1950 work commenced on several construction-islands in the middle of the IJsselmeer, the largest of which would be Lelystad-Haven which would house a community of dike-builders. The experience of the Noordoostpolder had shown that ground water from the old mainland would seep into the new land, causing ground sinkage and soil dehydration in the old land. It was therefore decided to detach the next polders from the mainland by leaving a string of peripheral lakes in between the two, resulting in a much longer encircling dike of some 90 km needing to be built for the polder.

The plans for a single southeastern polder had by this time given way for two separate polders that would have a joint hydrological infrastructure, with a dividing dike in the middle, the Knardijk, that will keep one polder safe should the other be flooded. The two main drainage canals that traverse the dike can be closed by weirs in such an event. The eastern polder would be the first of the two and the encircling dike began to take form in 1951, progressing nicely until February 1953 when a major flood struck the southwestern Netherlands (the event that would result in the Delta Works) and consequently people and machinery were transferred there for reparations. Work on Eastern Flevoland resumed in 1954 and the dike was finally closed on September 13 1956. The pumping stations started draining the polder that same day and they completed their task in June 1957. Three were built: the Wortman (diesel powered) by Lelystad-Haven, the Lovink near Harderwijk and the Colijn (both electrically powered) along the northern dike beside the Ketelmeer, all three built to an overcapacity with the future southern polder in mind.

A new element in the design of this polder was the intention to establish a larger city to serve as a regional centre for all the polders and perhaps the capital of a potential new province. This city, located centrally in the area of all the reclaimed lands, would be Lelystad (1966), named after the man who had played a crucial role in the design and realisation of the Zuiderzee Works. Other, more conventional settlements were already in existence by then; Dronten, the local major town, was founded in 1962, followed by two smaller satellite villages, Swifterbant and Biddinghuizen in 1963. These latter three would be incorporated in the new municipality of Dronten on January 1 1972; Lelystad would be large enough to form its own municipality and did so on January 1 1980.

Though agriculture was initially again the main purpose of the polder, the post-war period was to see a shift in the design goals for the new polders. More farming communities, similar to the Noordoostpolder, had originally been planned, but changing agricultural needs and increased motorised mobility meant many weren't necessary and thus their number was eventually reduced to just two, even though for one non-existent village, Larsen, building had been about to start when it was cancelled. However, the amount of agricultural land did not increase, rather it diminished as a result of the building of Lelystad (a city envisioned to eventually house at least 100,000 inhabitants) and assigning more than just infertile soil for forests and nature reserves, a trend that would continue in the next polder.

Land Usage of the Polders
in % of total surface area
Polder Size Agriculture Housing Nature Infrastructure
Wieringermeer 200 km² 87 %  1 %  3 % 9 %
Noordoostpolder 480 km² 87 %  1 %  5 % 7 %
Eastern Flevoland 540 km² 75 %  8 % 11 % 6 %
Southern Flevoland 430 km² 50 % 25 % 18 % 7 %
Southern Flevoland (Zuidelijk Flevoland) is the name of the fourth polder of the Zuiderzee Works, built adjacent to its larger sibling, Eastern Flevoland. Since its northeastern dike, the aforementioned Knardijk, already existed only 70 km of dike remained to be built; starting in early 1959 this was finished in October 1967.

Only one pumping station, the diesel powered De Blocq van Kuffeler, needed to be built because of the hydrological union of the two Flevolands; once the polder was finished it would simply join the previous three in maintaining the water-level of both polders. Before it could do that however the newest gemaal had to first drain the 430 km² polder of its water all by itself, completing its job in May 1968.

Due to the geographically favourable location of the southern polder to the heavily urbanised centre of the Netherlands and in particular Amsterdam, the planners devised a design that would include a large new urban area, to be called Almere, in order to relieve the housing shortage and increasing overcrowding on the old land. It was to be divided into 3 major settlements initially; the first, Almere-Haven (1976) situated along the Gooimeer (one of the peripheral lakes), the second and largest was to fulfill the role of city centre as Almere-Stad (1980) and the third was Almere-Buiten (1984) to the northwest towards Lelystad.

In between Lelystad and Almere was an area designated for heavy industries, but since enough space was still available on the old land for those industries this part of the polder was left alone for the mean time. After only a couple of years this landscape of shallow pools, islets and swamps became a popular resting and foraging area for many species of waterfowl, to the extent that it rapidly turned into a nature reserve of national significance. The Oostvaardersplassen as they are known are by origin accidental, but by the 1970s they had become the definitive destination for this section of the polder.

The centre of the polder most closely resembles the pre-war polders in that it is almost exclusively agricultural. In contrast, the southeastern part is dominated by extensive forests. Here is also found the only other settlement of the polder, Zeewolde (1984), again a more conventional town acting as the local centre. Zeewolde became a municipality at the same time as Almere on January 1 1984, which in the case of Zeewolde meant that the municipality existed before the town itself, with only farms in the surrounding land to be governed until the town started to grow.

The fifth polder

The fifth polder does not exist. At least, not yet, though it is unknown whether or not it will ever be built. It had been the intention to start building the southwestern polder, known as the Markerwaard, at several points during the project, but other polders had taken precendence. Parts of it have in fact been built; in 1941 it had been decided to begin work on the first section of dike, but the German occupier stopped construction in that same year. This dike originated on Marken, the last of the IJsselmeer islands, and went north for some 2 km where it ends abruptly today. After World War II the eastern polder was chosen as the next project, but Marken was not wholly neglected; on October 17 1957 a 3.5 km long dike was closed, running south of the now former island to the Holland mainland.

When construction started in 1959 on a new dike it had not yet been decided whether this would be the northern dike of Southern Flevoland or the southern dike of the Markerwaard, but the choice eventually fell to the former and another chance for the Markerwaard had passed. A minor flood near Amsterdam in 1960 had demonstrated the danger a large IJsselmeer still presented. A further planned element of the Markerwaard was subsequently executed: a 28 km long dike between Lelystad and Enkhuizen, including two complexes of locks and discharge sluices at either end, was to hydrologically split the IJsselmeer in two, with the largest portion (1250 km²) continuing as the IJsselmeer and the smaller lake (700 km²) being named the Markermeer. Construction of this dike, known later as the Houtribdijk and also the Markerwaarddijk, progressed only slowly, lasting from 1963 to 1975, after which it also served as an important road connection between the north of North Holland and the eastern Netherlands. The Houtribdijk did not however result in the construction of the rest of the Markerwaard, as had been hoped by many advocates of the polder to be.

The debate on whether to build the Markerwaard would continue for many years. The need for new agricultural land had mostly disappeared by this time and extra space for housing wasn't necessary in this region. The existing ecological and recreational value of the Markermeer was considered by many to be equal or superior to any potential such value the Markerwaard would offer. Doubts began to surface about the overall cost-effectiveness of the polder. The original post-war designs had called for a polder of some 410 km² and many different proposals were later put forth in an effort to combine the benefits of both the Markerwaard and Markermeer, but to no avail. After several cabinets had previously intended in principle to proceed with the Markerwaard, it was decided to indefinitely postpone the project in September 1986, though the possibility of the fifth polder has so far not been completely ruled out.

The loss of the Markerwaard did not effect plans to create a new province out of the polders. The Wieringermeer, long since part of North Holland, would not become a part of it, but the municipalities of the other three and the islands of the Noordoostpolder would together form the 12th province of the Netherlands, Flevoland. The need for a new province was not immediately clear; Urk and the Noordoostpolder had been part of Overijssel up to that point and Dronten fell under Gelderland. After the new municipalities of Southern Flevoland were established in 1984, belonging to no province as was the case with Lelystad, the provincial issue required renewed attention. With only six municipalities and without the Markerwaard the area was considered by opponents to be too light for an entire province, but the polder municipalities were unanimous in their desire: on January 1 1986 the province of Flevoland was inaugurated.

The Zuiderzee Works had come to an end. The administration responsible for construction and development of the new land had changed names over the years, but it had now served its purposes; in 1996 it was reorganised to become an ordinary administration in charge of the maintenance of the sluices, locks, bridges and dikes in the region. The Zuiderzee Works had successfully transformed the once capricious heart of the Netherlands into a fertile agricultural land with many new communities combined with an extensive fresh water supply and, although not originally envisioned, a collection of valuable ecological and recreational areas.

External links