A polder () is a low-lying tract of land that forms an artificial hydrology entity, enclosed by embankments known as levee. The three types of polder are:
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Land reclamation from a body of water, such as a lake or the seabed
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Floodplain separated from the sea or river by a dike
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separated from the surrounding water by a dike and subsequently drained; these are also known as , especially in Germany
The ground level in drained marshes subsidence over time. All polders will eventually be below the surrounding water level some or all of the time. Water enters the low-lying polder through infiltration and water pressure of groundwater, or rainfall, or transport of water by rivers and canals. This usually means that the polder has an excess of water, which is pumped out or drained by opening at low tide. Care must be taken not to set the internal water level too low. Polder land made up of peat (former marshland) will sink in relation to its previous level, because of peat decomposing when exposed to oxygen from the air.
Polders are at risk of flooding at all times, and care must be taken to protect the surrounding dikes. Dikes are typically built with locally available materials, and each material has its own risks: sand is prone to collapse owing to saturation by water; dry peat is lighter than water and potentially unable to retain water in very dry seasons. Some animals dig tunnels in the barrier, allowing water to infiltrate the structure; the muskrat is known for this activity and hunted in certain European countries because of it. Polders are most commonly, though not exclusively, found in river deltas, former , and coastal areas.
Flooding of polders has also been used as a military tactic in the past. One example is the flooding of the polders along the Yser River during World War I. Opening the sluices at high tide and closing them at low tide turned the polders into an inaccessible swamp, which allowed the Allied armies to stop the German army.
The Netherlands has a large area of polders: as much as 20% of the land area has at some point in the past been reclaimed from the sea, thus contributing to the development of the country. IJsselmeer is the most famous polder project of the Netherlands. Some other countries which have polders are Bangladesh, Belgium, Canada and China. Some examples of Dutch polder projects are Beemster, Schermer, Flevopolder and Noordoostpolder.
Etymology
The
Dutch language word polder derives successively from
Middle Dutch polre, from
Old Dutch polra, and ultimately from
pol-, a piece of land elevated above its surroundings, with the
augmentative suffix
-er and
Epenthesis -d-
page 155
Netherlands
The
Netherlands is frequently associated with polders, as its engineers became noted for developing techniques to drain wetlands and make them usable for agriculture and other development. This is illustrated by the saying "God created the world, but the Dutch created the Netherlands".
[Cf. Forrest Clingerman, Brian Treanor, Martin Drenthen, David Utsler, Interpreting Nature: The Emerging Field of Environmental Hermeneutics, Fordham University Press, 1 sep. 2013. The sentence stems from a poem by Archibald Pitcairn (1652–1713): Tellurem fecere dei, sua littora Belgae. C.D. van Strien, British Travellers in Holland During the Stuart Period: Edward Browne and John Locke as Tourists in the United Provinces, Leiden 1993, 164.]
The Dutch people have a long history of reclamation of marshes and fenland, resulting in some 3,000 polders
As a result of flooding disasters, water boards called waterschap (when situated more inland) or hoogheemraadschap (near the sea, mainly used in the Holland region)[Reh, W., Steenbergen, C., Aten, D. 2007. Sea of Land, The polder as an experimental atlas of Dutch landscape architecture. 344 pp, Uitgeverij Architectura & Natura. ] were set up to maintain the integrity of the water defences around polders, maintain the waterways inside a polder, and control the various water levels inside and outside the polder. Water boards hold separate elections, levy taxes, and function independently from other government bodies. Their function is basically unchanged even today. As such, they are the oldest democratic institutions in the country. The necessary cooperation among all ranks to maintain polder integrity gave its name to the Dutch version of third-way politics—the Polder Model.
The 1953 flood disaster prompted a new approach to the design of dikes and other water-retaining structures, based on an acceptable probability of overflowing. Risk is defined as the product of probability and consequences. The potential damage in lives, property, and rebuilding costs is compared with the potential cost of water defences. From these calculations follows an acceptable flood risk from the sea at one in 4,000–10,000 years, while it is one in 100–2,500 years for a river flood. The particular established policy guides the Dutch government to improve flood defences as new data on threat levels become available.
Major Dutch polders and the years they were laid dry include Beemster (1609–1612), Schermer (1633–1635), and Haarlemmermeerpolder (1852). Polders created as part of the Zuiderzee Works include Wieringermeerpolder (1930), Noordoostpolder (1942) and Flevopolder (1956–1968)
Examples of polders
Brazil
Several cities on the Paraíba Valley region (in the state of São Paulo) have polders on land claimed from the floodplains around the Paraíba do Sul river.
Bangladesh
Bangladesh has 139 polders, of which 49 are sea-facing, while the rest are along the numerous
Distributary of the Ganges-Brahmaputra-Meghna River delta. These were constructed in the 1960s to protect the coast from tidal flooding and reduce salinity incursion.
[ "Bangladesh polders under threat", Irin News] They reduce long-term flooding and waterlogging following
from
. They are also cultivated for agriculture.
[ "Bangladeshi project to enhance polders amidst climate woes" , Unearth News]
Belgium
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De Moeren, near Veurne in West Flanders
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Polders along the Yser river between Nieuwpoort and Diksmuide
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Polders of Muisbroek and Ettenhoven, in Ekeren and Hoevenen
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Polder of Stabroek, in Stabroek
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Kabeljauwpolder, in Zandvliet
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Scheldepolders on the left bank of Scheldt
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Uitkerkse polders, near Blankenberge in West Flanders
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Prosperpolder, near Doel, Antwerp and Kieldrecht.
Canada
China
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The city of Kunshan has over 100 polders.
History
The
Jiangnan region, at the Yangtze River Delta, has a long history of constructing polders. Most of these projects were performed between the 10th and 13th centuries.
The Chinese government also assisted local communities in constructing dikes for swampland water drainage.
The Lijia (里甲) self-monitoring system of 110 households under a
lizhang (里长) headman was used for the purposes of service administration and tax collection in the polder, with a
liangzhang (粮长, grain chief) responsible for maintaining the water system and a
tangzhang (塘长, dike chief) for polder maintenance.
Denmark
Finland
France
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Marais Poitevin
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Les Moëres, adjacent to the Flemish polder De Moeren in Belgium.
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Polders de Couesnon near Mont-Saint Michel in Normandy
Germany
In Germany, land reclaimed by diking is called a
koog. The German
Deichgraf system was similar to the Dutch and is widely known from
Theodor Storm's novella
The Rider on the White Horse.
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Altes Land near Hamburg
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Blockland and Hollerland near Bremen
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Nordstrand, Germany
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Bormerkoog and Meggerkoog near Friedrichstadt
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36 koogs in the district of Nordfriesland
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12 koogs in the district of Dithmarschen
In southern Germany, the term polder is used for recreated by opening dikes during river floodplain restoration, a meaning somewhat opposite to that in coastal context.
Guyana
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Black Bush Polder, Corentyne, Berbice.
India
Ireland
Italy
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Delta of the river Po River, such as Bonifica Valle del Mezzano
Japan
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Around the Ariake Sea in Kyushu, mainly in Saga Prefecture but also in Fukuoka and Kumamoto Prefectures
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Lake Hachirōgata was reclaim in 1964
Lithuania
Netherlands
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Achtermeer, the oldest polder, from 1533
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Alblasserwaard, containing the windmills of Kinderdijk, a World Heritage Site
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Alkmaar
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Andijk
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Anna Paulownapolder
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Beemster, a World Heritage Site
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Bijlmermeer
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Flevopolder, the largest artificial island in the world, last part drained in 1968
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's-Gravesloot
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Haarlemmermeer, containing Schiphol airport
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Krimpenerwaard
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Lauwersmeer
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Mastenbroek, one of the oldest medieval polders, drained around 1363-1364.
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Noordoostpolder
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Purmer
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Schermer
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Watergraafsmeer
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Wieringermeer
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Wieringerwaard
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Wijdewormer
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Zestienhoven, home of the Rotterdam The Hague Airport (Overschie), in the city of Rotterdam.
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Zuidplaspolder, along with Lammefjord in Denmark the lowest point of the European Union
Poland
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Vistula delta near Elbląg and Nowy Dwór Gdański
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Warta delta near Kostrzyn nad Odrą
Romania
Singapore
Slovenia
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The Ankaran Polder (), Semedela Polder (Semedelska bonifika), and Škocjan Polder (Škocjanska bonifika) in reclaimed land around Koper.
South Korea
Spain
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Parts of Málaga were built on reclaimed land
United Kingdom
United States
See also
Further reading
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Derex, Jean-Michel, Franco Cazzola (eds.) 2004. 2nd ed. 2013. Eau et développement dans l'Europe moderne. Paris, Maison des Sciences De L'Homme
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Farjon, J.M.J., J. Dirkx, A. Koomen, J. Vervloet & W. Lammers. 2001. Neder-landschap Internationaal: bouwstenen voor een selectie van gebieden landschapsbehoud. Alterra, Wageningen. Rapport 358 .
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Stenak, Morten. 2005. De inddæmmede Landskaber – En historisk geografi. Landbohistorik Selskab.
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Polders of the World. Keynotes International Symposium. 1982. Lelystad, The Netherlands
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Ven, G.P. van de (ed.) 1993, 4th ed. 2004. Man-made Lowlands. History of Water Management and Land Reclamation in the Netherlands, Matrijs, Utrecht.
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Wagret, Paul. 1972. Polderlands. London: Methuen.
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