After the Deltaworks

Battle against the water
After the construction of the Deltaworks, the people of Zeeland should have been feeling a great sense of relief. The chances of a disaster like the Flood of 1953 are a lot smaller, but that doesn’t mean that the battle against the water is over. The southern regions of the Netherlands are not only threatened by high sea water levels, but also by those of the mayor rivers. Scientists expect that, as a consequence of climate change, it will rain more often and more heavily, causing those rivers bursting their banks more often.

The exceptionally wet summer of 2004 (314 millimetres of precipitation against an average of 202 millimeters) caused a lot of flooding in many places and the rivers had to handle a lot of excess water due to the rain.
Relatively wet summers like those will, according to experts, occur more often in the future, which means that sea levels will rise due to climate change. To keep Zeeland and the rest of The Netherlands safe, additional protection is needed to only that in the coastal regions.

Turning point
Even though safety is the foremost consideration in water management, nature conservation and recreation also play important roles. The choice for an open dam instead of a closed one in the Oosterschelde was a turning point in the ideas regarding water management. While safety was used as a starting point, the interests of nature and the environment as well as fishing industries, recreation, agriculture, shipping industries and industry in general were also taken into account.

Thanks to the decision for an open dam, the unique salt water environment of the Oosterschelde remained, but the execution of the Deltaplan still had large consequences for nature. The tidal flow in the Oosterschelde decreased with a quarter and in certain places where seawater at first streamed unhindered, the dams diminished this flow, causing the water there to turn into (nearly) fresh water. Areas that used to flood at high tide dried up and places that used to dry up at low tide are now permanently flooded. Trenches and creeks are closed up and sandbanks have crumbled away. Saltwater fish have disappeared and a number of bird species have left. Other species replaced them.

Haringvliet

Developing nature
Since 1985, experiments are being done with nature development projects. In Haringvliet, Hollandsch Diep and Biesbosch nature is left to roam free. In some places, dykes have been breached and in other places drifting sand is left to drift wherever it wants. On and around the old work island Neeltje Jans, beaches, dunes and bird islands have been installed. The concrete and steel of the Deltaworks has become a home for all kinds of algae and sea shells.

After the closure of the Haringvliet in 1971, the water is slowly turning fresh. To spare nature as much as possible, special tunnels have been made in a several openings of the Haringvliet locks so fish can swim from the Haringvliet to the North Sea and back, even when the locks are closed.

However, as migratory fish like salmon and trout appeared to have trouble reaching their spawning areas, in 2011 the decision was made to keep a tiny gap between the locks. The fish will are then able to pass through the locks and a more natural transition between salt seawater and sweet, fresh river water will form. This, however, also means that the western part of the Haringvliet will become more salty. The locks will not be opened until 2018.

Until then, the government works on compensating measures. A sweet water area will be made near Voorne-Putten as well as Goeree-Overflakkee. To provide clients on Goeree-Overflakkee and Schouwen-Duiveland with good drinking water, Evides Watercompany wins surface water from the Haringvliet and makes sure it gets purified.

Project sea defences
Whilst Zeeland has become a lot safer due to the dams and the storm surge barrier, the sea defences have also become stronger. The Wet op de Waterkering (Law on the Dam) (1990) dictates how strong a dyke and its stone cladding must be. For Zeeland, the norm is that the sea defences have to be able to resist a super storm surge, which occurs on average once every 4000 years.

According to a report from 2008, the Deltacommittee has to take into account a rise in sea levels of up to 1.3 metres in the year 2100. Furthermore, the committee predicts that more and more salt water will contaminate the land from the rivers and the groundwater. Fresh water supplies could possibly be in danger because of this.

Projectbureau Zeeweringen

Fresh water reservoir
The committee gives several recommendations for the period leading up to 2100. Elevating safety levels by adjusting sea defences is not the only important part, but also to stop hindering the discharge capacity of rivers. Rivers need more space. Krammer-Volkerak and Zoommeer should be used for temporary “storage” of water coming from the Rijn and the Maas. Another recommendation is the strengthening of the strategic function of the IJsselmeer as a fresh water reservoir for the north and west of The Netherlands.

An important weapon in the battle against the water is sand supplementation. By pumping sand along the whole coastline, the coast can “regrow”. The loss of marshlands will be restricted that way. Also, the Wadden area should “grow along” with the rising of the sea level by sand supplementation. Additionally, the lifetime of the storm surge barrier has to be increased.

Deltaprogramme
After the Deltacommittee presented the report to the government in 2008, the committee was abolished. The government accepted the advice, which resulted in the Delta law, a Deltaprogramme and the appointment of Wim Kuijken as Deltacommissioner. In several places in the Netherlands, the Delta law and Deltaprogramme are taken into account.

Farmer Beer Water
In Noord-Limburg, local authorities and the Water Board started the project Waterklaar. The goal of this project is to retain water and prevent superfluous water and flooding by detaching the rainwater from the sewerage systems. With the project Boer Bier Water (Farmer Beer Water), businesses (like the brewery Bavaria), local farmers and the government work together to protect fresh water sources against contamination. Bavaria no longer dumps waste water, but purifies it and distributes it amongst farmers and horticulturalists.

The provinces Gelderland and Utrecht, 28 local authorities and water authority Vallei en Veluwe (Valley and Veluwe) will be working together on a climate sustainable future based on the manifesto Ruimtelijke Adaptatie (Environmental Adaptation). The goal is to map out exactly how vulnerable Gelderland and Utrecht are when it comes to superfluous water, flooding, heat and drought. After that, plans will be made to make the area less vulnerable.

Underground irrigation
At the moment, experiments are being done with “subirrigation”, based on the manifesto. This is a form of underground irrigation in which water is spread underground through the means of a drainage system. This keeps roots damp and it causes less water loss through evaporation.

Other works
Over the past 50 years, many important hydraulic engineering projects have been carried out in the Delta area next to the Deltaworks. The Zeelandbrug (bridge) (1963 – 1965) and the Westerscheldetunnel (1998 – 2003) have made Zeeland more accessible.

Up until 1965, the ferry between Zierikzee (on the island of Schouwen-Duiveland) and Kats (on the island of Noord-Beveland) was the only way to cross the Oosterschelde. During those years, there were plans to build a dam between Schouwen-Duiveland and Noord-Beveland, which was to be completed in 1978 at the earliest. Eventually, it wasn’t a solid dam but a storm surge barrier, that wasn’t fully operable and useable until 1986.

North—south connection
The ferry could not handle the strongly increased traffic in the 60’s anymore and the need for a good north-south connection grew. That’s why, in 1963, the province of Zeeland finalises the order for the Zeeland bridge between Schouwen-Duiveland and Noord-Beveland to be built. With its 5 kilometres in length, the bridge – then still called the Oosterschelde bridge – becomes the longest in the Netherlands. The Zeeland bridge exists of 54 pillars with spans at intervals of 95 metres. There is also a passageway for ships by making part of the bridge, which is 40 metres wide, moveable.

The bridge is officially opened on 15 December 1965 by Queen Juliana. In April of 1967, the Oosterschelde bridge is renamed Zeeland bridge. Until 1993, users of the bridge had to pay toll, after then the bridge has been toll free. The opening of the Zeeland bridge makes Schouwen-Duiveland a lot more accessible. This leads to mass tourism to Schouwen-Duiveland. Especially the Westhoek with its dunes and 18 kilometres of beach profits from this.

Zeelandbrug Watersnoodmuseum

Drilled tunnel
Another important link in the north-south connection is the Westerscheldetunnel between Ellewoutsdijk on Zuid-Beveland and Terneuzen on Zeeuws-Vlaanderen. Road traffic can drive easily from Rotterdam to Belgium via the Westerscheldetunnel and Zeeland bridge.

The construction of the 6.6 kilometre long tunnel is technically speaking a unique project. The main advantage of a drilled tunnel is in this case the fact that ships can pass by unhindered. Most tunnels in Europe are drilled in relatively hard, rocklike materials. That seems harder than drilling in the relatively soft riverbed of the Westerschelde, but it is not. It is the first time in the history of West-Europe that such a long and deep tunnel is drilled through sand and clay.

To drill in such a weak underground, a tunnel boring machine is specially made in Germany for the Westerscheldetunnel. It works with hydrostatic pressure. The boring machine makes contact with the ground that has to be dug out at the front. A cutting wheel with six arms and in total 64 teeth dig the ground out layer by layer.

Cutting head
The boring machine is enveloped by a metal cutting head with a diameter of eleven metres that keeps the drilled hole intact and makes sure that no sand and water comes into the tunnel. Whenever the machine heads a bit further, a part of the definite tunnel wall is placed.

The deeper the machine gets, the higher the pressure becomes. At the deepest point – 60 metres below sea level – the pressure (7 bar) is seven times higher than the normal air pressure at the surface of the earth. During drilling, a normal air pressure is artificially maintained, because working there would otherwise be impossible.

The Westerscheldetunnel replaces the ferry services between Vlissingen and Breskens, and Kruiningen and Perkpolder. During bad weather, the services were often cancelled, which meant that someone who had to go from Middelburg on Walcheren to Oostburg in Zeeuws-Vlaanderen, had to wait for the ferry to start going again or take a detour via Noord-Brabant. The opening of the Westerscheldetunnel in 2003 changed that.

Earlier plans
The idea to build a tunnel under the Westerschelde is not a new one. As early as in the 1930’s , businessmen from Goes came up with a similar plan, but the feasibility of the plan causes disagreements amongst specialists. At the end of the 1960’s there are once again plans for a fixed connection between Zeeuws-Vlaanderen and Zuid-Beveland. The plan consists of a combination of a suspension bridge and a tunnel which is submerged at the bottom of the Westerschelde.

The plan is regarded as too expensive in the end. From 1986 onwards, the stream of ideas begins to flow again. First, the old plans are revitalised and reconsidered, but later the idea for a drilled tunnel forms. In 1996 – after years of discussion – the decision is made and the construction of the Westerscheldetunnel begins in 1998. Queen Beatrix officially opens the Westerscheldetunnel on March 14, 2003.

Westerscheldetunnel

Lauwersmeer (1969)
In addition to the Deltaworks in the southwest of the Netherlands, other measures were taken after the Flood of 1953 to protect the land and the people against the sea. In 1969 the Lauwers sea, an inlet of the Waddenzee on the border between the provinces of Groningen and Friesland in the north of The Netherlands is closed off, forming the Lauwersmeer (lake). The risk of flooding of the hinterland during a storm surge was, according to the governors at that time, too high.

There were various options at the time to defuse the threat posed by the Lauwerszee. Conservationists and fishermen pleaded for raising the surrounding dykes. The local people of Friesland and Groningen wanted a dam to close it off, because they felt it would be safer. Eventually, following public pressure, the latter option was chosen.

Work starts in 1961. A dam of 13 kilometres long has to be built, complete with several locks and sluices. The procedure used is very similar to that of the construction of the Deltaworks. To close the gap, caissons and open caissons are used. The open caissons are built on location, on the work island of Lauwersoog. On May 23rd 1969, the last caisson is sunk and the sea has become a lake.

National park
Closing off the Lauwers sea resulted in big changes to nature in the area. As the water slowly turned brackish, seals lose their beloved habitat. They are forced to leave for other parts of the Wadden Sea. During the first few years after the dam was completed, nature was left to its own devices in the area, without human intervention.

From 1980 onwards, nature conservation is actively encouraged and regulated. Herds of cattle and sheep are turned out to graze, initially only in summer, but later throughout the whole of the year. Fresh water fish migrate to the area, making it attractive to birds like great cormorants, spoonbills and diving ducks. Later, moles, roe deer, rabbits and foxes also move in. And so a unique new natural habitat evolves. The area was awarded the status of National Park in November 2003. Apart from being a unique national park, Lauwersmeer is also a busy recreational area. The former work island of Lauwersoog has been transformed into a harbour town with a ferry to Schiermonnikoog. In the neighbouring area – which is attractive to sailors, surfers and mud-flat walkers – bungalow parks, campsites and sailing schools have been built.

The Afsluitdijk (1920-1933)
Between Noord-Holland and Friesland, the Afsluitdijk (roughly translated: Closing Dyke) is built. The Zuiderzee is closed off by the 32 kilometre long dyke, which is part of the Zuiderzee works. It is an important step in the protection of The Netherlands against the water.

The idea of closing off the Zuiderzee had already been suggested by Hendrik Stevin in the seventeenth century. However, his plans for land reclamation were not feasible in those days. Steam-driven pumps, needed to remove the water once the dam was built, don’t yet exist. The plans are dismissed.

Around 1880, the discussion about the reclamation of the Zuiderzee flares up again. The planners realise that they will never be able to raise the funds for such a big project and therefore need the support of the government. In 1885 they set up the Zuiderzee foundation, and engineer Cornelis Lely is named advisor.

World War I
In 1891 Lely becomes minister of water management and finalises his plans for land reclamation in that same year. There are, however, too many doubts if the benefits will outweigh the costs and so the plans are put to rest, just like Stevin’s. In 1913, Queen Wilhelmina believes it is time to carry out the plans regardless. But in 1914 the First World War breaks out and Lely’s plans are shelved once again.

When The Netherlands is hit by the Zuiderzee flood in 1916, the plans of Cornelis Lely receive renewed attention. Lely wants to construct a dyke from Noord-Holland via the existing island Wieringen to Friesland. Once the dyke is there, the land underneath the Zuiderzee can be reclaimed.

The second, never executed, phase of Lely’s plans includes the construction of a dyke from Den Helder to Terschelling, and from there to Ameland, Schiermonnikoog and Rottum. That would have closed off most of the Waddenzee.
In 1918, the bill for the reclamation of the Zuiderzee is approved by Parliament and implementation starts in 1920.

Afsluitdijk Watersnoodmuseum
Afsluitdijk

Drainage sluices
Firstly, drainage sluices are being built. These are used to remove the excess water from the IJsselmeer (a lake) into the Waddenzee during ebb tide. In the Afsluitdijk, five sets of five drainage sluices are being used: three sets near Den Oever (Lorentz locks) and two on the Kornwederzand (Stevin locks). Because in certain areas the seabed isn’t suitable for building locks on, the line of the dyke is moved north slightly in 1923. This explains the slight bend in the Afsluitdijk.

The Afsluitdijk is 90 metres wide along the waterline. The locks are each 12 metres wide and 4 metres deep. During the construction of the Afsluitdijk, 27 million cubic metres of sand and 15 million cubic metres of boulder clay were used. Boulder clay is a mix of boulders, gravel, sand and clay. It is a hard and tough material that came from Scandinavia during the second last ice age. Thanks to the rocks, which are a several decimetres in size, the boulder clay stays in place, even when the flow speed is 4 metres per second.

The dyke is founded upon “mattresses” of woven willow branches, which were sunk by dumping rocks on top of them. Once it was discovered that the wood is inundated by naval shipworm (a species of salt water clam known for causing major damage to submerged wood structures), barite – a type of rock from Germany – is used to reinforce the dyke foundation.

In 1932, the last segment – De Vlieter – is closed off. A year later, the Afsluitdijk is opened for traffic. Across the Afsluitdijk a road connects Noord-Holland with Friesland.