The Delta Works () is a series of construction projects in the southwest of the

Netherlands , Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...

to protect a large area of land around the Rhine–Meuse–Scheldt delta from the sea. Constructed between 1954 and 1997, the works consist of

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aqua ...

s, sluices, locks, dykes,

levee A levee ( or ), dike (American English), dyke (British English; see American and British English spelling differences#Miscellaneous spelling differences, spelling differences), embankment, floodbank, or stop bank is an elevated ridge, natural ...

s, and storm surge barriers located in the

provinces A province is an administrative division within a country or state. The term derives from the ancient Roman , which was the major territorial and administrative unit of the Roman Empire's territorial possessions outside Italy. The term ''provi ...

South Holland South Holland ( ) is a province of the Netherlands with a population of over 3.8 million as of January 2023 and a population density of about , making it the country's most populous province and one of the world's most densely populated areas. ...

and

Zeeland Zeeland (; ), historically known in English by the Endonym and exonym, exonym Zealand, is the westernmost and least populous province of the Netherlands. The province, located in the southwest of the country, borders North Brabant to the east ...

. 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 Zuiderzee Works () is a system of dams and Levee, dikes, land reclamation and water drainage work, which was the largest hydraulic engineering project undertaken by the Netherlands during the twentieth century. The project involved the dammin ...

, the Delta Works have been declared one of the Seven Wonders of the Modern World by the

American Society of Civil Engineers The American Society of Civil Engineers (ASCE) is a tax-exempt professional body founded in 1852 to represent members of the civil engineering profession worldwide. Headquartered in Reston, Virginia, it is the oldest national engineering soci ...

History

Due to indecision and the

Second World War World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

, little action was taken. In 1950 two small estuary mouths, the Brielse Gat near

Brielle Brielle (), also called Den Briel in Dutch and Brill in English, is a town and historic seaport in the western Netherlands, in the province of South Holland, on the north side of the island of Voorne-Putten, at the mouth of the New Maas. The for ...

and the Botlek near

Vlaardingen Vlaardingen () is a large town and List of municipalities of the Netherlands, municipality in South Holland in the Netherlands. It is located on the north bank of the Nieuwe Maas river at the confluence with the Oude Maas. The municipality admin ...

were dammed. After the

North Sea flood of 1953 The 1953 North Sea flood () was a major flood caused by a heavy storm surge that struck the Netherlands, north-west Belgium, England and Scotland. Most sea defences facing the surge were overwhelmed, resulting in extensive flooding. The ...

, 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".

Delta law and conceptual framework

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: * Major areas to be protected from flooding are identified. These are called "dike ring areas" because they are protected by a ring of primary sea defences. * The cost of flooding is assessed using a statistical model involving damage to property, lost production, and a given amount per human life lost. * For the purpose of this model, a human life is valued at €2.2 million (2008 data). * The chances of a significant flood within the given area are calculated. This is done using data from a purpose-built flood simulation lab, as well as empirical statistical data regarding water wave properties and distribution. Storm behaviour and spring tide distribution are also taken into account. 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: * North and South Holland (excluding Wieringermeer): 1 per 10,000 years * Other areas at risk from sea flooding: 1 per 4,000 years * Transition areas between high land and low land: 1 per 2,000 years 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. * South Holland at risk from river flooding: 1 per 1,250 years * Other areas at risk from river flooding: 1 per 250 years. 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 The sea level has been rising from the end of the last ice age, which was around 20,000 years ago. Between 1901 and 2018, the average sea level rose by , with an increase of per year since the 1970s. This was faster than the sea level had e ...

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

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 ' (Zeeland Lake). 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 The leisure industry is the segment of business focused on recreation, entertainment, sports, and tourism (REST)-related products and services. The field has developed to the point of having university degrees and disciplines focused on it, such ...

, 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. In addition, building components of the reinforcements are designed in a way that they support formation of entire ecosystems. As part of the revision, the Room for the River projects, enabled nature to occupy space by lowering or widening the river bed. 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. 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. Although the new plan brought along additional cost, it was received favourably. 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 when environmental awareness and ecological effects of engineering projects were barely taken into consideration. Although the level of awareness for the environment grew throughout the years, the Delta Project has caused numerous irreversible effects on the environment in the past. Blocking the

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime enviro ...

mouths did reduce the length of dykes that otherwise would have to be built 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. In addition, rivers experienced an increase in sedimentation 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 at 3.3 billion

guilder Guilder is the English translation of the Dutch and German ''gulden'', originally shortened from Middle High German ''guldin pfenninc'' (" gold penny"). This was the term that became current in the southern and western parts of the Holy Rom ...

. 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 The Marshall Plan (officially the European Recovery Program, ERP) was an American initiative enacted in 1948 to provide foreign aid to Western Europe. The United States transferred $13.3 billion (equivalent to $ in ) in economic recovery pr ...

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. Nevertheless, in 2012 the total costs were already set on around $13 billion.

Current status

The original plan was completed by the Europoortkering which required the construction of the Maeslantkering in the

Nieuwe Waterweg The Nieuwe Waterweg ("New Waterway") is a ship canal in the Netherlands from Scheur, het Scheur (a branch of the Rhine-Meuse-Scheldt delta) west of the town of Maassluis to the North Sea at Hook of Holland: the #Maasmon, Maasmond, where the Nieu ...

between

Maassluis Maassluis () is a town in the western Netherlands, in the province of South Holland. The municipality had a population of in and covered of which was water. It received town rights in 1811. History Maassluis was founded circa 1340 as a se ...

and

Hook of Holland Hook of Holland (, ) is a coastal village in the southwestern corner of Holland, hence the name; ''hoek'' means "corner" and was in use before the word ''wikt:kaap#Dutch, kaap'' – "cape". The English translation using Hook is a false cognate of t ...

and the Hartelkering in the Hartel Canal near

Spijkenisse Spijkenisse () is a large town in the Provinces of the Netherlands, province of South Holland, Netherlands. Following an administrative reform in 2015, it is part of the List of municipalities of the Netherlands, municipality of Nissewaard, and ha ...

. The works were declared finished after almost forty years in 1997. 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. 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 A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, flat ...

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.

Projects

# # Timeline Delta Works # ImageSize = width:1200 height:120 PlotArea = left:25 bottom:20 width:1000 height:100 AlignBars = early DateFormat = yyyy Period = from:1950 till:2010 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:5 start:1950 Colors = id:grey value:gray(0.5) PlotData= bar:Leaders color:red width:25 align:left fontsize:S shift:(0,-40) from:1950 till:2010 shift:(-10,20) textcolor:blue at:1953 mark:(line,grey) text:1953 North Sea flood textcolor:black at:1965 mark:(line,grey) text:1965 Grevelingendam at:1983 mark:(line,grey) text:1983 Markiezaatskade at:1997 mark:(line,grey) text:1997 Maeslant Barrier shift:(-10,32) at:1950 mark:(line,grey) text:1950 afdamming Botlek at:1958 mark:(line,grey) text:1958 Hollandse IJssel Storm Barrier at:1986 mark:(line,grey) text:1986 Eastern Scheldt Barrier at:1997 mark:(line,grey) text:1997 Hartel Barrier shift:(-10,44) at:1950 mark:(line,grey) text:1950 Brielse Maasdam at:1960 mark:(line,grey) text:1960 Zandkreekdam at:1969 mark:(line,grey) text:1969 Volkerakdam at:1987 mark:(line,grey) text:1987 Oesterdam shift:(-10,56) at:1952 mark:(line,grey) text:1952 afdamming Braakman at:1961 mark:(line,grey) text:1961 Veerse Gatdam at:1971 mark:(line,grey) text:1971 Haringvliet sluices at:1987 mark:(line,grey) text:1987 Philipsdam shift:(-10,68) at:1971 mark:(line,grey) text:1971 Brouwersdam The works that are part of the Delta Works are listed in chronological order with their year of completion:

References

External links

Delta Works.Org / Deltawerken.Com official website for the Delta Works
{{Coord, 51.65, N, 3.72, E, region:NL_scale:500000, display=title * * * Flood control in the Netherlands Water resource management in the Netherlands Science and technology in the Netherlands 1954 establishments in the Netherlands 20th-century architecture in the Netherlands