Polder

A polder is a piece of land that people have made by building walls called dikes around low-lying areas. These areas are often former lakes, seabeds, flood plains, or marshes that have been separated from water. Once the water is drained out, the land can be used for farming or building homes.

Because polders are lower than the surrounding water, they need special care to keep the water out. Water can seep into the polder from underground, rain, or rivers, so pumps and sluices are used to remove extra water. If the water level inside the polder is too low, it can cause problems, especially for land made of peat, which sinks when it dries out.

Polders are most common in places like river deltas and coastal areas. The Netherlands has many polders, with about 20% of its land reclaimed from the sea. Famous polders there include the IJsselmeer, Beemster, Schermer, Flevopolder, and Noordoostpolder. Other countries with polders include Bangladesh, Belgium, Canada, and China.

Etymology

The word polder comes from Dutch. It started with the old Dutch word polre, which came from an even older word polra. These words described a piece of land that was higher than the land around it. Over time, the word changed and spread to many other languages.

Netherlands

The Netherlands is well known for its polders. Dutch engineers are famous for their skills in turning wet areas into useful land for farming and building. A popular saying there is, "God made the world, but the Dutch made the Netherlands".

The Dutch have a long history of turning wet marshes and areas into dry land, creating about 3,000 polders across the country. By 1961, they had turned nearly half of the Netherlands, which is 18,000 square kilometres, into usable land from the sea. About half of all polders in northwest Europe are found in the Netherlands. The first dikes in Europe were built during Roman times, and the first polders were made in the 1100s. The oldest polder still around is Achtermeer, built in 1533.

Because of serious floods in the past, special groups called water boards were created to protect and care for the dikes around polders. These water boards have their own elections and taxes and work separately from other government groups. They are some of the oldest democratic groups in the country. Their job has stayed the same even today.

After a big flood in 1953, the Dutch changed how they design dikes and water barriers. They now decide how strong these barriers need to be based on how likely it is that they could break and how much damage might happen. This helps them make smart choices about protecting the land.

Some big Dutch polders and when they were made dry include Beemster (1609–1612), Schermer (1633–1635), and Haarlemmermeerpolder (1852). Polders made as part of the Zuiderzee Works include Wieringermeerpolder (1930), Noordoostpolder (1942) and Flevopolder (1956–1968).

Examples of polders

Brazil

Several cities in the Paraíba Valley region of São Paulo have polders on land claimed from the floodplains around the Paraíba do Sul river.

Bangladesh

Bangladesh has 139 polders, with 49 facing the sea and the rest along the distributaries of the Ganges-Brahmaputra-Meghna River delta. These were built in the 1960s to protect the coast from tidal flooding and reduce water from salt. They help prevent long-term flooding and waterlogging after big storms from tropical cyclones. The land is also used for farming.

Belgium

• De Moeren, near Veurne in West Flanders
• Polders along the Yser river between Nieuwpoort and Diksmuide
• Polders of Muisbroek and Ettenhoven, in Ekeren and Hoevenen
• Polder of Stabroek, in Stabroek
• Kabeljauwpolder, in Zandvliet
• Scheldepolders on the left bank of the Scheldt
• Uitkerkse polders, near Blankenberge in West Flanders
• Prosperpolder, near Doel, Antwerp and Kieldrecht.

Canada

• Tantramar Marshes
• Holland Marsh
• Pitt Polder Ecological Reserve
• Grand Pré, Nova Scotia
• Minas Basin

China

The city of Kunshan has over 100 polders.

History

The Jiangnan region, at the Yangtze River Delta, has a long history of building polders. Most of these projects were done between the 10th and 13th centuries. The Chinese government also helped local communities build dikes to drain swampland water. A system where 110 households were grouped under a headman was used for managing services and taxes in the polder, with special roles for keeping the water system and dikes maintained.

Denmark

• Filsø
• Kolindsund
• Lammefjorden

Finland

• Söderfjärden
• Munsmo
• Two polders near Vassor in Korsholm

France

• Marais Poitevin
• Les Moëres, next to the Flemish polder De Moeren in Belgium.
• Polders de Couesnon near Mont-Saint Michel in Normandy

Germany

Main article: Koog

In Germany, land reclaimed by building dikes is called a koog. The Deichgraf system was similar to the Dutch system and is well known from Theodor Storm's story The Rider on the White Horse.

• Altes Land near Hamburg
• Blockland and 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 word polder is used for retention basins made by opening dikes during river floodplain restoration, which is a bit different from its meaning near the coast.

Guyana

• Black Bush Polder, Corentyne, Berbice.

India

• Kuttanad Region, Kerala

Ireland

• Lough Swilly, County Donegal. Near Inch Island and Newtowncunningham.

Italy

• Delta of the river Po, such as Bonifica Valle del Mezzano

Japan

• Around the Ariake Sea in Kyushu, mainly in Saga but also in Fukuoka and Kumamoto Prefectures
• Lake Hachirōgata in Akita was reclaimed in 1964, creating the town of Ōgata

Lithuania

• Rusnė Island

Netherlands

• Achtermeer, the oldest polder, from 1533
• Alblasserwaard, containing the windmills of Kinderdijk, a World Heritage Site
• Alkmaar
• Andijk
• Anna Paulownapolder
• Beemster, a World Heritage Site
• Bijlmermeer
• Flevopolder, the largest artificial island in the world, last part drained in 1968
• 's-Gravesloot
• Haarlemmermeer, containing Schiphol airport
• Krimpenwaard
• Lauwersmeer
• Mastenbroek, one of the oldest medieval polders, drained around 1363-1364.
• Noordoostpolder
• Prins Alexanderpolder
• Purmer
• Schermer
• Watergraafsmeer
• Wieringermeer
• Wieringerwaard
• Wijdewormer
• Zestienhoven, home of the Rotterdam The Hague Airport (Overschie), in the city of Rotterdam.
• Zuidplaspolder, along with Lammefjord in Denmark the lowest point of the European Union

Poland

• Vistula delta near Elbląg and Nowy Dwór Gdański
• Warta delta near Kostrzyn nad Odrą

Romania

• Danube Delta

Singapore

• Parts of Pulau Tekong

Slovenia

• The Ankaran/Ancarano Polder (Slovene: Ankaranska bonifika), Semedela Polder (Semedelska bonifika), and Škocjan Polder (Škocjanska bonifika) in reclaimed land around Koper/Capodistria.

South Korea

• Parts of the coast of Ganghwa Island, next to the river Han in Incheon
• Delta of the river Nakdong in Busan
• Saemangeum in North Jeolla Province

Spain

• Parts of Málaga were built on reclaimed land

United Kingdom

• Traeth Mawr
• Sunk Island, on the north shore of the Humber east of Hull
• Caldicot and Wentloog Levels along the Severn Estuary in South Wales
• Parts of The Fens
  • Branston Island, by the River Witham outside the conventional area of the fens but connected to them.
• Parts of the coast of Essex
• Some land along the River Plym in Plymouth
• Some land around Meathop east of Grange-over-Sands, reclaimed as a side-effect of building a railway embankment
• The Somerset Levels and North Somerset Levels
• Romney Marsh
• Sealand, Flintshire
• Humberhead Levels

United States

• New Orleans
• Sacramento – San Joaquin River Delta