Delta Works

 ( Flood Control In The Netherlands ) 

The Delta Works () 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. Constructed between 1954 and 1997, the works consist of , , locks, Levee, , and floodgate 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 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 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.

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.

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 and strengthening sea and river Levee. 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.

id:grey value:gray(0.5)
     

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:

• Flood control in the Netherlands
• Lauwersmeer
• Megaproject
• Thames Barrier
• Zuiderzee Works
• Johan van Veen
• Pieter Jacobus Wemelsfelder

• Delta Works.Org / Deltawerken.Com official website for the Delta Works