User:Solitude/Delta Works

The Delta Works are an elaborate flood defense system in the Netherlands, involving dikes, locks, dams, sluices and canals. Construction started with the Storm Surge Barrier Hollandse IJssel in 1954 right after the flood disaster of 1953, and was finished with the completion of the Maeslantkering in 1997. The Works offer flooding protection to an estimated 300.000 people in the Dutch provinces Zeeland, Zuid-Holland and Noord-Brabant, the entire project cost an estimated &euro;5 billion, which comes down to &euro;16.000 per head of the affected population. The most notable Delta Works dam, The Oosterscheldedam is sometimes referred to as the eighth wonder of the world, and has been declared one of the modern Seven Wonders of the World by the American Society of Civil Engineers.

Flood Disaster 1953
On the night of 31 January, early morning 1 February 1953 the Netherlands was hit by a heavy northwestern storm, while at the same time a spring tide was active as well. The at the time inedequate dikes could not resist this combined force, several dikes burst, flooding large sections of land in the southern provinces of Zeeland, Zuid-Holland and Noord-Brabant. The flooding water killed more than 1,800 people and forced the evacuation of 70,000 more, also 10.000 animals drowned, and 4,500 buildings were destroyed.

Construction
The Delta Works were built over a period of almost fourty years. They are a system involving locks, sluices, channels, dams and other control methods to prevent flooding.


 * Storm Surge Barrier Hollandse IJssel (1958)
 * Zandkreekdam (1960) - in the Zandkreek strait (g)
 * Veerse Gatdam (1961) - closes the Veerse Meer (f)
 * Grevelingendam (1965) - in lake Grevelingen (n)
 * Volkerakdam (1969)
 * Haringvlietdam (1971)
 * Brouwersdam (1971) - in lake Grevelingen (n)
 * Markiezaatskade (1983)
 * Oosterscheldedam (1986)
 * Oesterdam (1987)
 * Philipsdam (1987)
 * Bathse spuisluis (1987)
 * Maeslantkering (1997)



Storm Surge Barrier Hollandse IJssel
The Storm Surge Barrier is located in the Hollandse IJssel, near Rotterdam and Krimpen aan de IJssel, total cost for this barrier was 18 million euros. The later construction of the Maeslantkering made the Storm Surge Barrier obsolete.

The Hollandse IJssel was, and still is, an important shipping trade route, and also serves as a fresh water supply for a large part of Zuid Holland. This is why the waterway was not closed off with a dam, but a specially designed flood barrier was used featuring two moveable sluices hanging between two concrete towers. In the default position the sluice gates are raised and ships can sail underneath, thereby passing the barrier. In the case of an emergency the gates are lowered, closing down the river entirely. The nearby lock can then be used by ships to pass the barrier.

Construction for the first part of the Delta Works was started merely a year after the disaster of 1953. In January 1954 dredging for the barrier initiated, and on 6 May 1958 the first floodgate was lowered for testing, later that year the Storm Surge Barrier was officially opened. The barrier was nicknamed Algerabrug, after former Chief of Traffic and Water management, J. Algera, who resigned shortly before completion of the barrier.



Zandkreekdam
The ‘three-island project’ proposed in 1953 called for two dams to link the island of Walcheren with Noord-Beveland and Zuid-Beveland. Construction on the shortest of these two dams, the Zandkreekdam, initiated soon after the completion of the Storm Surge Barrier in the Hollandse IJssel. The dam consists of two parts, the first part is a sluice, about 140m long and 20m wide. This sluice had to be completed first as the Zandkreekdam blocks an important shipping route, used by ships sailing to and from Vlissingen. The second part, the actual dam, is 690m long and was closed and completed using sinkable caissons in 1960. Completion of this dam was an historical event for the people of Noord Beveland, the Zandkreekdam was the first connection to the mainland, which broke their dependence on ferry transportation.



Veerse Gatdam
The Veerse Gatdam (gat = hole) closed the Veerse Gat, creating the Veerse Meer. The dam is 2.8 km in length, running from Walcheren to Noord-Beveland. As with the construction of the Zandkreekdam, sinkable caissons were used, quite inventive caissons in the case of the Veerse Gatdam. The caissons contained holes that allows the tide to flow freely through the caissons during construction, this allowed the dam to be built without the tide exuding a strong force during construction. The holes in the caissons were closed in the last phase of construction. Nowdays, the closed off Veerse Meer is a popular tourist attraction, especially for windsurfers.



Grevelingendam
The 6 km long Grevelingendam is a utility dam, it was not necessary for flood protection itself but was built to lessen the burden of the water on the construction of the Haringvlietdam, the Brouwersdam, and the Oosterschelde barrier by stopping the current. Construction of the dam connecting Schouwen-Duiveland and Goeree-Overvlakkee started in 1957, 4 years after the flood. The central sand bank in lake Grevelingen was raised with sand extracted from the bottom of the North sea, the southern gap was then closed using the familiar method of sinkable caissons.

The northern gap was closed using an inventive aerial_tramway, which could drop large rocks in the lake, creating the dam's structure. The railway spanned from the island Goeree-Overvlakkee to the central sand bank, supported by a concrete pillar positioned halfway. Ten cable cars were used, each having its own driver and engine, each carrying a large net which held the rocks. On average the cars travelled at 5 m/s and carried a load of 10.000 kg.

As with the Veerse Gatdam, the newly created lake turned into a attraction, popular with divers and kayakers.



Volkerakdam
The Volkerakdam closed off the Volkerak, a heavily travelled waterway between the North sea and the city of Antwerp in Belgium, part of the Schelde-Rijnkanaal. To allow ships to pass the damn even during construction, three locks were built first. In the next phase, a brige was built using 14 caissons, which can be lowered in case of an extreme storm tide. This bridge created a, nowadays well travelled, traffic route between Noord-Brabant and Rotterdam.



Haringvlietdam
The sixth large construction of the Delta Works, the Haringvlietdam closes of the Haringvliet, protecting Goeree-Overvlakkee, Voorne Putten and the Hoekse Waard agains flooding. The entire dam is 4.5 km long and has a lock to allow ships to pass and even a canal system to allow fish to swim in and out of the Haringvliet when all the sluices and locks are closed. Second only to the Oosterschelde barrier, this dam was the most timeconsuming project, construction started as early as 1957 and was finished in 1971. In the first phase more than 21.000 pilings were driven into the ground to support the entire structure.

The second phase started in 1961 with construction of the sluices. As the Haringvliet is the endpoint for the large rivers Rhine (originating in the Swiss Alps) and the Meuse (originating in France). It was therefore decided that the dam should not close of the Haringvliet and would have to be able to let through large volumes of water. A complex 1 km long construction with 17 sluices was built, capable of letting through 25.000 m&sup3; water per second. During severe storms, all the sluice gates can be closed, closing of the entire Haringvliet. For the third phase, the technique using the cable railway was employed, used before on the Grevelingendam, the Haringvlietdam was completed in 1971.



Brouwersdam
The Brouwersdam was built to defend Goeree-Overvlakkee and Schouwen-Duiveland from floods, this positions the dam in lake Grevelingen (a good 30 m deep at this location), west of the Grevelingendam. Construction for the 6 km long dam was started in 1964, soon after completion of the Grevelingendam. Two large sand banks, the Middelplaat and the Kabbelaarsplaat, were located in the center of the dam's path. The two banks were close and were therefore made into one bigger bank, leaving a north and a south section of dam to be built.

Closing the deep southern gully (the Brouwershavense Gat) required another cable railway to be built which could deliver 600.000 tons of stones and rocks in 10 weeks. Technology for the cable railway had progressed, the new trolleys were equipped with gas turbines instead of diesel engines, giving the trolleys a maximum speed of 7.5 m/s. The northern section of the dam would be built in less deep water (De Kous), so caissons could be used, which have the distinct advantage of allowing the tide to flow freely during construction.

In 1978 a lock, the Brouwerssluis, was added to the Brouwersdam to allow ships to pass.

Maeslantkering
The Maeslantkering is the storm surge barrier in the Nieuwe Waterweg waterway near Hoek van Holland, Netherlands. It closes automatically when needed.