Delta Works

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The Delta Works (Dutch : Deltawerken) is a series of construction projects in the southwest of the Netherlands to protect a large area of land around the Rhine-Meuse-Scheldt delta from the sea. The works consist of dams, sluices, locks, dykes, levees, and storm surge barriers located in the provinces of South Holland and Zeeland.


The aim of the dams, sluices, and storm surge barriers was to shorten the Dutch coastline, thus reducing the number of dikes that had to be raised. Along with the Zuiderzee Works, the Delta Works have been declared one of the Seven Wonders of the Modern World by the American Society of Civil Engineers.


The estuaries of the rivers Rhine, Meuse and Schelde have been subject to flooding over the centuries. After building the Afsluitdijk (1927 1932), the Dutch started studying the damming of the Rhine-Meuse Delta. Plans were developed to shorten the coastline and turn the delta into a group of freshwater coastal lakes. By shortening the coastline, fewer dikes would have to be reinforced.

Due to indecision and the Second World War, little action was taken. In 1950 two small estuary mouths, the Brielse Gat near Brielle and the Botlek near Vlaardingen were dammed. After the North Sea flood of 1953, a Delta Works Commission was installed to research the causes and develop measures to prevent such disasters in future. They revised some of the old plans and came up with the "Deltaplan".

Unlike the Zuiderzee Works, the Delta Plan's purpose is largely defensive and not for land reclamation. [1] The Delta Plan is a national programme and demands collaboration between the national government, provincial authorities, municipal authorities and the water boards. The plan consisted of blocking the estuary mouths of the Oosterschelde, the Haringvliet and the Grevelingen. This reduced the length of the dikes exposed to the sea by 700 kilometres (430 mi). The mouths of the Nieuwe Waterweg and the Westerschelde were to remain open because of the important shipping routes to the ports of Rotterdam and Antwerp. The dikes along these waterways were to be heightened and strengthened. The works would be combined with road and waterway infrastructure to stimulate the economy of the province of Zeeland and improve the connection between the ports of Rotterdam and Antwerp.

Delta law and conceptual framework

Zeeland Bridge Colijnsplaat - Zeelandbrucke.jpg
Zeeland Bridge
Oosterscheldekering OosterscheldeKering.jpg

An important part of this project was fundamental research to come up with long term solutions, protecting the Netherlands against future floods. Instead of analysing past floods and building protection sufficient to deal with those, the Delta Works commission pioneered a conceptual framework to use as norm for investment in flood defences.

The framework is called the 'Delta norm'; it includes the following principles:

The most important "dike ring area" is the South Holland coast region. It is home to four million people, most of whom live below normal sea level. The loss of human life in a catastrophic flood here can be very large because there is typically little warning time with North Sea storms. Comprehensive evacuation is not a realistic option for the Holland coastal region.

The commission initially set the acceptable risk for complete failure of every "dike ring" in the country at 1 in 125,000 years. But, it found that the cost of building to this level of protection could not be supported. It set "acceptable" risks by region as follows:

River flooding causes less damage than salt water flooding, which causes long-term damage to agricultural lands. Areas at risk from river flooding were assigned a higher acceptable risk. River flooding also has a longer warning time, producing a lower estimated death toll per event.

These acceptable risks were enshrined in the Delta Law (Dutch: Deltawet). This required the government to keep risks of catastrophic flooding within these limits and to upgrade defences should new insights into risks require this. The limits have also been incorporated into the new Water Law (Waterwet), effective from 22 December 2009.

The Delta Project (of which the Delta Works are a part) has been designed with these guidelines in mind. All other primary defences have been upgraded to meet the norm. New data elevating the risk assessment on expected sea level rise due to global warming has identified ten 'weak points.' These have been upgraded to meet future demands. The latest upgrades are made under the High Water Protection Program.

Alterations to the plan during the execution of the Works

Scale model of the Maeslantkering Schaalmodel Maeslantkering.jpg
Scale model of the Maeslantkering

During the execution of the works, changes were made in response to public pressure. In the Nieuwe Waterweg, the heightening and the associated widening of the dikes proved very difficult because of public opposition to the planned destruction of important historic buildings to achieve this. The plan was changed to the construction of a storm surge barrier (the Maeslantkering) and dikes were only partly built up.

The storm-surge barrier

The Delta Plan originally intended to create a large freshwater lake, the Zeeuwse Meer (Zeeland Lake). [1] This would have caused major environmental destruction in Oosterschelde, with the total loss of the saltwater ecosystem and, consequently, the harvesting of oysters. Environmentalists and fishermen combined their efforts to prevent the closure; they persuaded parliament to amend the original plan. Instead of completely damming the estuary, the government agreed to build a storm surge barrier. This essentially is a long collection of very large valves that can be closed against storm surges.

The storm surge barrier closes only when the sea-level is expected to rise 3 metres above mean sea level. Under normal conditions, the estuary's mouth is open, and salt water flows in and out with the tide. As a result of the change, the weak dikes along the Oosterschelde needed to be strengthened. Over 200 km of the dike needed new revetments. The connections between the Eastern Scheldt and the neighboring Haringvliet had to be dammed to limit the effect of the salt water. Extra dams and locks were needed at the east part of the Oosterschelde to create a shipping route between the ports of Rotterdam and Antwerp. Since operating the barrier has an effect on the environment, fisheries and the water management system, decisions made on opening or closing the gate are carefully considered. Also the safety of the surrounding dykes are affected by barrier operations.

Environmental policy implementations

In an attempt to restore and preserve the natural system surrounded by the dykes and storm-surge barrier, the concept 'building with nature' was introduced in revised Delta Program updates after 2008. The new integrated water management plan not only takes into account protection against flooding, but also covers water quality, leisure industry, economic activities, shipping, environment and nature. Whenever possible, existing engineering constructions would be replaced by more 'nature friendly' options in an attempt to restore natural estuary and tides, while still protecting against flooding. [2] In addition, building components of the reinforcements are designed in a way that they support formation of entire ecosystems. [3] As part of the revision, the Room for the River projects, enabled nature to occupy space by lowering or widening the river bed. [4] In order to establish this, agricultural flood plains are turned into natural parks, excavated farmland is used for wild vegetation and newly excavated lakes and bypasses create habitats for fish and birds. [5] Along the coast, natural sand is added each year to allow sand to blow freely through the dunes instead of having the dunes held in place by planted vegetation or revetments. [6] Although the new plan brought along additional cost, it was received favourably.[ citation needed ] The re-considerations of the Delta Project indicated the growing importance of integrate environmental impact assessments in policy-making.

Environmental effects

The Delta Project of which the Delta Works are part of was originally designed in a period of time in what environmental awareness and ecological effects of engineering projects were barely taken into consideration. [7] Although the level of awareness for the environment grew throughout the years, the Delta Project has caused numerous irreversible[ citation needed ] effects on the environment in the past. Blocking the estuary mouths did reduce the length of dykes that otherwise would have to be build to protect against floods, but it also led to major changes in the water systems. For example, the tides disappeared, which resulted in a less smooth transition from sea water into fresh water. Flora and fauna suffered from this noticeable change. [8] In addition, rivers got covered up by polluted sludge, since there was no longer an open passage to the sea.

Project costs

The projects of the Delta Plan are financed with the Delta Fund. In 1958, when the Delta law was accepted under the Delta Works Commission, the total costs were estimated on a 3.3 billion guilder. This was at that time equal to 20% of national GDP. This amount was spread out over the 25 years that it would take to complete the massive engineering project. The Delta works were mostly financed by the national budget, with a contribution of the Marshall Plan of 400 million guilder. In addition, the Dutch natural gas discovery contributed massively to the finance of the project. At completion in 1997, costs were set on 8.2 billion guilder. [9] Nevertheless, in 2012 the total costs were already set on[ clarification needed ] around $13 billion. [10]

Current status

The original plan was completed by the Europoortkering which required the construction of the Maeslantkering in the Nieuwe Waterweg between Maassluis and Hoek van Holland and the Hartelkering in the Hartel Canal near Spijkenisse. The works were declared finished after almost forty years in 1997. In reality, the works were finished on 24 August 2010 with the official opening of the last strengthened and raised retaining wall near the city of Harlingen, Netherlands.[ citation needed ]

Due to climate change and relative sea-level rise, the dikes will eventually have to be made higher and wider. This is a long term uphill battle against the sea. The needed level of flood protection and the resulting costs are a recurring subject of debate, and involve a complicated decision-making process. In 1995 it was agreed in the Delta Plan Large Rivers and Room for the River projects that about 500 kilometres of insufficient dyke revetments were reinforced and replaced along the Oosterschelde and Westerschelde between 1995 and 2015. After 2015, under the High Water Protection Program, additional upgrades are made. [11]

In September 2008, the Delta Commission presided by politician Cees Veerman advised in a report that the Netherlands would need a massive new building program to strengthen the country's water defenses against the anticipated effects of global warming for the next 190 years. The plans included drawing up worst-case scenarios for evacuations and included more than €100 billion, or $144 billion, in new spending through the year 2100 for measures, such as broadening coastal dunes and strengthening sea and river dikes. The commission said the country must plan for a rise in the North Sea of 1.3 meters by 2100 and 4 meters by 2200. [12]


Delta Works

The works that are part of the Delta Works are listed in chronological order with their year of completion:

Delta Works Data
Stormvloedkering Hollandse IJssel (Algerakering)19541958Flood barrier Hollandse IJssel (river) South Holland near Krimpen aan den IJssel
Zandkreekdam 19591960Dam Zandkreek, Veerse Gat (Oosterschelde)Between Noord-Beveland and Zuid-Beveland on the east
Veerse Gatdam 19601961Dam Veerse Gat (Oosterschelde)Between Noord-Beveland and Zuid-Beveland on the west
Grevelingendam 19581965Dam Grevelingenmeer Between Tholen and Schouwen-Duiveland
Volkerakdam 19571969Dam Volkerak, Hollands Diep Meuse and Oosterschelde Between South Holland and Zeeland
Haringvlietdam 19581971Dam and Flood barrier Haringvliet (Rhine and Meuse (river))Between Voorne-Putten and Goeree-Overflakkee
Brouwersdam 19641971Dam Grevelingenmeer Between Goeree-Overflakkee and Schouwen-Duiveland
Markiezaatskade 19801983Dam Scheldt–Rhine Canal, Markiezaatsmeer Between Zuid-Beveland and Molenplaat
Oosterscheldekering 19601986Flood barrier Oosterschelde Between Schouwen-Duiveland and Noord-Beveland
Oesterdam 19791987Dam Oosterschelde, Scheldt–Rhine Canal Between Tholen and Zuid-Beveland
Philipsdam 19761987Dam Oosterschelde Between Grevelingendam and Sint Philipsland
Bathse spuisluis 19801987 Lock Volkerak, Markiezaatsmeer, Oosterschelde Bath, Zeeland
Maeslantkering 19881997Flood barrier Nieuwe Waterweg (Rhine)Downstream Rotterdam South Holland
Hartelkering 19911997 storm surge barrier Hartelkanaal Near Spijkenisse, South Holland

See also

Related Research Articles

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Eastern Scheldt estuary in Zeeland, Netherlands

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Goeree-Overflakkee Island and Municipality in South Holland, Netherlands

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Haringvliet large inlet of the North Sea

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Scheldt–Rhine Canal

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Maeslantkering Dutch storm surge barrier

The Maeslantkering is a storm surge barrier on the Nieuwe Waterweg, in South Holland, Netherlands. Part of the Delta Works, the barriers are controlled by a supercomputer, and automatically close when Rotterdam is threatened by floods.

North Sea flood of 1953 Late January-early February 1953 North sea flood storm

The 1953 North Sea flood was a major flood caused by a heavy storm that occurred on the night of Saturday, 31 January 1953 and morning of Sunday, 1 February 1953. The floods struck the Netherlands, Belgium and the United Kingdom.

Biesbosch National Park National park in the Netherlands

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The Oosterscheldekering, between the islands Schouwen-Duiveland and Noord-Beveland, is the largest of the thirteen ambitious Delta Works series of dams and storm surge barriers, designed to protect the Netherlands from flooding from the North Sea. The construction of the Delta Works was a response to the widespread damage and loss of life in the North Sea flood of 1953.

Levee breach situation where a levee fails or is intentionally breached, causing the previously contained water to flood

A levee breach or levee failure is a situation where a levee fails or is intentionally breached, causing the previously contained water to flood the land behind the levee.

Flood barrier specific type of floodgate, designed to prevent a storm surge or spring tide from flooding the protected area behind the barrier

A flood barrier, surge barrier or storm surge barrier is a specific type of floodgate, designed to prevent a storm surge or spring tide from flooding the protected area behind the barrier. A surge barrier is almost always part of a larger flood protection system consisting of floodwalls, levees, and other constructions and natural geographical features.

Yerseke Village in Zeeland, Netherlands

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Flood control in the Netherlands

Flood control is an important issue for the Netherlands, as due to its low elevation, approximately two thirds of its area is vulnerable to flooding, while the country is densely populated. Natural sand dunes and constructed dikes, dams, and floodgates provide defense against storm surges from the sea. River dikes prevent flooding from water flowing into the country by the major rivers Rhine and Meuse, while a complicated system of drainage ditches, canals, and pumping stations keep the low-lying parts dry for habitation and agriculture. Water control boards are the independent local government bodies responsible for maintaining this system.

Merwede river in South Holland

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Rhine–Meuse–Scheldt delta river delta in the Netherlands and Belgium

The Rhine–Meuse–Scheldt delta or Helinium is a river delta in the Netherlands formed by the confluence of the Rhine, the Meuse and the Scheldt rivers. The result is a multitude of islands, branches and branch names that may at first sight look bewildering, especially as a waterway that appears to be one continuous stream may change names as many as seven times, e.g. Rhine → Bijlands Kanaal → Pannerdens Kanaal → Nederrijn → Lek → Nieuwe Maas → Het Scheur → Nieuwe Waterweg. Since the Rhine contributes most of the water, the shorter term Rhine Delta is commonly used. However, this name is also used for the delta where the Alpine Rhine flows into Lake Constance, so it is clearer to call the larger one Rhine–Meuse delta, or even Rhine–Meuse–Scheldt delta, as the Scheldt ends in the same delta. By some calculations, the delta covers 25,347 km2 (9,787 sq mi), making it the largest in Europe.

Flood control methods used to reduce or prevent the detrimental effects of flood waters

Flood control methods are used to reduce or prevent the detrimental effects of flood waters. Flood relief methods are used to reduce the effects of flood waters or high water levels.

Hartelkering storm surge barrier in Spijkenisse, Netherlands

The Hartelkering is a storm surge barrier in Spijkenisse, Netherlands. The barrier is part of the Europoortkering, itself part of the Delta Works project and is designed to close the Hartelkanaal in case of a storm surge.


The Europoortkering or barrier of the Europoort is a program of engineering works in addition to the Delta Plan, designed to protect the maritime access routes from the port of Rotterdam and thus, the entire South Holland against storms and tides.

Johan van Veen Dutch engineer (1893-1959)

Johan van Veen was a Dutch hydraulic engineer and is considered the father of the Delta Works.


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Coordinates: 51°39′N3°43′E / 51.65°N 3.72°E / 51.65; 3.72