A polder (Dutch pronunciation: [ˈpɔldər] ( listen )) is a low-lying tract of land that forms an artificial hydrological entity, enclosed by embankments known as dikes. The three types of polder are:
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 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 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 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 Dutch 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 epenthetical -d-. The word has been adopted in thirty-six languages.
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".
The Dutch have a long history of reclamation of marshes and fenland, resulting in some 3,000 polders 18,000 square kilometres (6,800 sq mi), was reclaimed from the sea. About half the total surface area of polders in north-west Europe is in the Netherlands. The first embankments in Europe were constructed in Roman times. The first polders were constructed in the 11th century. The oldest extant polder is the Achtermeer polder, from 1533.nationwide. By 1961, about half of the country's land,
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)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)
Bangladesh has 123 polders, of which 49 are sea-facing, while the rest are along the numerous distributaries of the Ganges-Brahmaputra-Meghna River delta. 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.
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.
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 .
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.
Flevoland is the 12th and youngest province of the Netherlands, established in 1986, when the Southern and Eastern Flevopolders, together with the Noordoostpolder were merged into one provincial entity. It is in the centre of the country in the former Zuiderzee, which was turned into the freshwater IJsselmeer by the closure of the Afsluitdijk in 1932. Almost all of the land belonging to Flevoland was reclaimed in the 1950s and 1960s while splitting the Markermeer and Bordering lakes from the IJsselmeer. As to dry land, it is the smallest province of the Netherlands at 1,412 km2 (545 sq mi), but not gross land as that includes much of the waters of the fresh water lakes (meres) mentioned. The province has a population of 423,021 as of January 2020 and consists of six municipalities. Its capital is Lelystad and its most populous city is Almere.
The IJsselmeer, also known as Lake IJssel in English, is a closed off inland bay in the central Netherlands bordering the provinces of Flevoland, North Holland and Friesland. It covers an area of 1,100 km2 (420 sq mi) with an average depth of 5.5 m (18 ft). The river IJssel flows into the IJsselmeer.
The Zuiderzee or Zuider Zee was a shallow bay of the North Sea in the northwest of the Netherlands, extending about 100 km inland and at most 50 km wide, with an overall depth of about 4 to 5 metres (13–16 feet) and a coastline of about 300 km. It covered 5,000 km2 (1,900 sq mi). Its name is Dutch for "southern sea", indicating that the name originates in Friesland, to the north of the Zuiderzee. In the 20th century the majority of the Zuiderzee was closed off from the North Sea by the construction of the Afsluitdijk, leaving the mouth of the inlet to become part of the Wadden Sea. The salt water inlet changed into a fresh water lake now called the IJsselmeer after the river that drains into it, and by means of drainage and polders, an area of some 1,500 km2 (580 sq mi) was reclaimed as land. This land eventually became the province of Flevoland, with a population of nearly 400,000 (2011).
The geography of the European Netherlands is unusual in that much of its land has been reclaimed from the sea and is below sea level, protected by dikes. It is a small country with a total area of 41,545 km2 (16,041 sq mi) and ranked 131st. With a population of 17.4 million and density of 521/km2 (1,350/sq mi) makes it the second most densely populated member of the European Union after Malta, and the 12th most densely populated country in the world, behind only three countries with a population over 16 million. Consequently, the Netherlands is highly urbanized.
The Zuiderzee Works is a man-made system of dams and dikes, land reclamation and water drainage work, in total the largest hydraulic engineering project undertaken by the Netherlands during the twentieth century. The project involved the damming of the Zuiderzee, a large, shallow inlet of the North Sea, and the reclamation of land in the newly enclosed water using polders. Its main purposes are to improve flood protection and create additional land for agriculture.
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 dams, sluices, locks, dykes, levees, and storm surge barriers located in the provinces of South Holland and Zeeland.
Beemster[ˈbeːmstər](listen) is a municipality in the Netherlands, in the province of North Holland. The Beemster is the first so-called polder in the Netherlands that was reclaimed from a lake, the water being extracted from the lake by windmills. The Beemster Polder was dried during the period 1609 through 1612. It has preserved intact its well-ordered landscape of fields, roads, canals, dykes and settlements, laid out in accordance with classical and Renaissance planning principles. A grid of canals parallels the grid of roads in the Beemster. The grids are offset: the larger feeder canals are offset by approximately one kilometer from the larger roads.
The Afsluitdijk is a major dam and causeway in the Netherlands. It was constructed between 1927 and 1932 and runs from Den Oever in North Holland province to the village of Zurich in Friesland province, over a length of 32 kilometres (20 mi) and a width of 90 metres (300 ft), at an initial height of 7.25 metres (23.8 ft) above sea level.
Schokland is a former island in the Dutch Zuiderzee, in the municipality of Noordoostpolder. Schokland was an elongated strip of peat land which ceased to be an island when the Noordoostpolder was reclaimed from the sea in 1942. It is now just a slightly elevated part of the polder, with a still partly intact retaining wall of the waterfront of Middelbuurt. On 1 April 2014, it had 8 inhabitants, but according to Statistics Netherlands there are five people living on the former island.
A koog or groden is a type of polder found on the North Sea coast of Germany that is established by the construction of dykes enclosing the land which is then drained to form marshland. This type of land reclamation is also used along rivers. In general, a koog is protected by embankments known as dykes (Deiche).
Kinderdijk is a village in the municipality of Molenlanden, in the province of South Holland, Netherlands. It is located about 15 km east of Rotterdam.
Land reclamation, usually known as reclamation, and also known as land fill, is the process of creating new land from oceans, seas, riverbeds or lake beds. The land reclaimed is known as reclamation ground or land fill.
Jan Adriaanszoon Leeghwater was a Dutch architect, mill builder and hydraulic engineer.
Waterwolf, or Water-wolf is a Dutch word that comes from the Netherlands, which refers to the tendency of lakes in low lying peaty land, sometimes previously worn-down by men digging peat for fuel, to enlarge or expand by flooding, thus eroding the lake shores, and potentially causing harm to infrastructure, or death. The term waterwolf is an example of zoomorphism, in which a non-living thing is given traits or characteristics of an animal. The traits of a wolf most commonly given to lakes include “something to be feared”, “quick and relentless”,” an enemy of man”.
De Biesbosch National Park is one of the largest national parks of the Netherlands and one of the last extensive areas of freshwater tidal wetlands in Northwestern Europe. The Biesbosch consists of a large network of rivers and smaller and larger creeks with islands. The vegetation is mostly willow forests, although wet grasslands and fields of reed are common as well. The Biesbosch is an important wetland area for waterfowl and has a rich flora and fauna. It is especially important for migrating geese.
The St. Elizabeth's flood of 1421 was a flooding of the Grote Hollandse Waard, an area in what is now the Netherlands. It takes its name from the feast day of Saint Elisabeth of Hungary which was formerly November 19. It ranks 20th in the list of worst floods in history. During the night of November 18 to November 19, 1421, a heavy storm near the North Sea coast caused the dikes to break in a number of places and the lower lying polder land was flooded. A number of villages were swallowed by the flood and were lost, causing between 2,000 and 10,000 casualties. The dike breaks and floods caused widespread devastation in Zeeland and Holland.
A levee breach or levee failure is a situation where a levee fails or is intentionally breached, causing the previously contained water to flood the land behind the levee.
Flood control is an important issue for the Netherlands, as due to its low elevation, approximately two thirds of its area is vulnerable to flooding, while the country is densely populated. Natural sand dunes and constructed dikes, dams, and floodgates provide defense against storm surges from the sea. River dikes prevent flooding from water flowing into the country by the major rivers Rhine and Meuse, while a complicated system of drainage ditches, canals, and pumping stations keep the low-lying parts dry for habitation and agriculture. Water control boards are the independent local government bodies responsible for maintaining this system.
In the Netherlands, water boards or regional water authorities are regional government bodies charged with managing water barriers, waterways, water levels, water quality and sewage treatment in their respective regions. These regional water authorities are among the oldest forms of local government in the Netherlands, some of them having been founded in the 13th century.
Land reclamation in the Netherlands has a long history. As early as in the 14th century, the first reclaimed land had been settled. Much of the modern land reclamation has been done as a part of the Zuiderzee Works since 1918.
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