A polder (Dutch pronunciation: [ˈpɔldər] ( listen)) is a low-lying tract of land enclosed by dikes that forms an artificial hydrological entity, meaning it has no connection with outside water other than through manually operated devices. There are three types of polder:
Land reclaimed from a body of water, such as a lake or the sea bed
Flood plains separated from the sea or river by a dike
The ground level in drained marshes subsides 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 ground water, 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 sluices 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 from 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 fenlands and
Flooding of polders has also been used as a military tactic in the
past. One example is the flooding of the polders along the
1 Etymology 2 Polders and the Netherlands 3 Examples of polders
3.1 Bangladesh 3.2 Belgium 3.3 Canada 3.4 Finland 3.5 France 3.6 Germany 3.7 Guyana 3.8 India 3.9 Ireland 3.10 Italy 3.11 Lithuania 3.12 Netherlands 3.13 Poland 3.14 Slovenia 3.15 South Korea 3.16 United Kingdom 3.17 United States
4 See also 5 References 6 External links
Etymology From Dutch polder ("polder"), from Middle Dutch polre, from Old Dutch polra, ultimately from pol- "part of land, elevated above its surroundings"; with augmentative suffix -er and epenthetical -d-. Polders and the Netherlands
Pumping station in Zoetermeer, Netherlands. The polder lies lower than the surrounding water on the other side of the dike. The Archimedes' screws are clearly visible.
Examples of polders Bangladesh Bangladesh has 123 polders, of which 49 are sea-facing. These were constructed in the 1960s to protect the coast from tidal flooding and reduce salinity incursion. They reduce long-term flooding and waterlogging following storm surges from tropical cyclones. They are also cultivated for agriculture. Belgium
De Moeren, near
Söderfjärden Munsmo Two polders (totally 3 km2) near Vassor in Korsholm
Marais Poitevin Les Moëres, adjacent to the Flemish polder De Moeren in Belgium.
Germany Main article: Koog In Germany, land reclaimed by dyking 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.
Altes Land near Hamburg Blockland & Hollerland near Bremen Nordstrand, Germany Bormerkoog and Meggerkoog near Friedrichstadt 36 koogs in the district of Nordfriesland 12 koogs in the district of Dithmarschen
In southern Germany, the term polder is used for retention basins recreated by opening dikes during river floodplain restoration, a meaning somewhat opposite to that in coastal context. Guyana
Black Bush Polder, Corentyne, Berbice.
Lough Swilly, Co. Donegal. Near
Delta of the river Po, such as Bonifica Valle del Mezzano
Alblasserwaard, containing the windmills of Kinderdijk, a World
Beemster, a World Heritage Site
Parts of the coast of Ganghwa Island, adjacent to the river Han in
Delta of the river Nakdong in Busan
Sunk Island, on the north shore of the
Branston Island, by the
Parts of the coast of Essex
Some land along the
New Orleans Sacramento – San Joaquin River Delta
Flood control in the Netherlands Afsluitdijk Land reclamation IJsselmeer Zuiderzee Works Windpump
^ "Kijk naar de geschiedenis". Rijkswaterstaat. Retrieved
2008-01-21. [permanent dead link]
^ Ley, Willy (October 1961). "The Home-Made Land". For Your
Information. Galaxy Science Fiction. pp. 92–106.
^ "waterschap". Archived from the original on 2012-11-02.
^ "Bangladesh polders under threat", Irin News
^ "Bangladeshi project to enhance polders amidst climate woes"
Archived 2014-04-08 at the Wayback Machine., Unearth News
^ "Rain continues to throw a challenge in Kuttanad". The Hindu. The
Hindu Group. 2011. Retrieved 2011-06-10.
^ Thampatti, Manorama (March 1999). "Rice Bowl in Turmoil: The
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. Morten Stenak. 2005. De inddæmmede Landskaber - En historisk geografi. Landbohistorik Selskab. Ven, G.P. van de (red.) 1993. Leefbaar laagland: geschiedenis van waterbeheersing en landaanwinning in Nederland. Matrijs, Utrecht. Wagret, P. 1972. Polderlands. London: Methuen.
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