Polder
A polder isn't just a piece of land; it's a testament to human ingenuity—an artificially created world wrested from the water. These low-lying tracts, meticulously enclosed by embankments and continuously drained, represent humanity's enduring effort to expand habitable land. They are living laboratories of engineering, where communities literally live below sea level, a fascinating balancing act that defines entire regions and challenges our understanding of natural boundaries. Polders are artificial low-lying lands, constantly managed to prevent flooding from surrounding higher water levels. Their creation involves sophisticated engineering, primarily dike building and continuous water pumping, making them vulnerable to environmental and structural challenges. While famously associated with the Netherlands, polders are a global solution for land reclamation and flood protection, found in diverse regions worldwide.
AI Summary
A polder isn't just a piece of land; it's a testament to human ingenuity—an artificially created world wrested from the water. These low-lying tracts, meticulously enclosed by embankments and continuously drained, represent humanity's enduring effort to expand habitable land. They are living laboratories of engineering, where communities literally live below sea level, a fascinating balancing act that defines entire regions and challenges our understanding of natural boundaries.
- Polders are artificial low-lying lands, constantly managed to prevent flooding from surrounding higher water levels.
- Their creation involves sophisticated engineering, primarily dike building and continuous water pumping, making them vulnerable to environmental and structural challenges.
- While famously associated with the Netherlands, polders are a global solution for land reclamation and flood protection, found in diverse regions worldwide.
What is a Polder?
Imagine a world shaped not by mountains and rivers alone, but by human will—a landscape born from the purposeful control of water. This is the essence of a polder. It's a low-lying tract of land that forms an artificial hydrological entity, meaning it's been intentionally separated from surrounding bodies of water, usually by sturdy embankments known as dikes.
Three Ways to Make Land
Polders come in a few distinct varieties, each demonstrating a different aspect of this incredible land-making process. They can be land reclaimed directly from a body of water, like a lake or the seabed itself. Or they might be natural floodplains, carefully walled off from a threatening sea or river.
Then there are marshes, vast wetlands that are first enclosed by dikes and then thoroughly drained. These are sometimes called 'koogs,' especially in regions like Germany. Each type requires constant vigilance and engineering to keep the water at bay.
Living Below Sea Level
Here's the remarkable truth about polders: almost all of them eventually end up below the surrounding water level, at least some of the time. The very act of draining marshland causes the ground, especially peat soils, to subside or sink over time as the organic matter decomposes when exposed to oxygen. It's a constant, slow descent.
The Constant Battle Against Water
So, how do you keep a polder dry when it's literally lower than the water around it? Water constantly tries to enter through infiltration, groundwater pressure, rainfall, or even transport via rivers and canals. This means polders almost always have an excess of water.
To combat this, water must be continuously pumped out or drained through sluices, gates that can be opened at low tide. This delicate balance must be carefully maintained; setting the internal water level too low can actually accelerate the subsidence of peat-rich lands, creating an even greater challenge.
Perils and Protections
Polders are inherently at risk of flooding, making dike protection paramount. Dikes are typically constructed from locally available materials, each with its own vulnerabilities. Sand, for instance, can collapse if water-saturated, while dry peat is lighter than water and might fail to retain it during dry seasons.
Even wildlife poses a threat! Animals like the muskrat are notorious for digging tunnels within dikes, compromising their structural integrity and allowing water to seep through. In some European countries, these diligent burrowers are even hunted because of the damage they inflict on crucial water defenses.
Polders in Warfare
Remarkably, the unique vulnerability of polders has also been leveraged as a military tactic. During World War I, for example, polders along Belgium's Yser River were intentionally flooded. By strategically opening sluices at high tide and closing them at low tide, the land transformed into an impassable swamp, effectively halting the Imperial German army's advance.
A Dutch Word, A Global Concept
The very word 'polder' is Dutch in origin, stemming from the Middle Dutch 'polre' and ultimately from 'pol-,' meaning a piece of land elevated above its surroundings. Over centuries, this innovative concept and its name have been adopted into dozens of languages, reflecting its global significance.
The Polder Nation: The Netherlands
When we think of polders, our minds often turn to the Netherlands, and for good reason. Its engineers practically wrote the book on draining wetlands and reclaiming land, giving rise to the famous saying, 'God created the world, but the Dutch created the Netherlands.' It's a nation forged as much by human hands as by natural forces.
A History Forged in Water
The Dutch have been mastering land reclamation for centuries. Their long history of battling the sea and swamps has resulted in over 3,000 polders across the country. By the mid-20th century, a staggering 18,000 square kilometers—nearly half of the country's land area—had been reclaimed from the sea, showcasing an unparalleled dedication to creating new ground.
Governing the Water: Water Boards
The constant threat of flooding led to a unique form of governance in the Netherlands: the water boards. These highly specialized democratic institutions, some dating back to the 11th century, were established to maintain dikes, manage waterways, and control water levels. They operate independently, levying taxes and holding their own elections.
This deep-rooted tradition of cooperation to maintain polder integrity even inspired the term 'Polder Model' in Dutch politics—a consensus-based approach to decision-making that prioritizes collaboration across various societal groups for the greater good.
Modern Flood Defenses and Iconic Projects
A devastating flood disaster in 1953 spurred a new, highly scientific approach to dike design in the Netherlands, focusing on acceptable probability and risk assessment. Today, Dutch flood defenses are designed to withstand floods with probabilities as low as one in 4,000 to 10,000 years for sea floods.
Among the most impressive Dutch polders are the Beemster (drained 1609-1612), the Schermer (1633-1635), and the monumental Haarlemmermeerpolder (1852), which now hosts Schiphol Airport. The Zuiderzee Works also created vast new lands like the Noordoostpolder (1942) and the Flevopolder (1956–1968), the largest artificial island in the world.
Polders Around the World
While the Netherlands is its most famous proponent, polder technology is a global phenomenon, adapted to diverse environments and cultures. It's a testament to a universal human desire to protect and expand territory.
Asia's Polder Landscapes
In Bangladesh, a nation crisscrossed by river deltas, 139 polders were constructed in the 1960s to safeguard against tidal flooding and saltwater intrusion. They provide crucial protection from storm surges and enable vital agricultural cultivation.
China's Jiangnan region, within the Yangtze River Delta, boasts a long history of polder construction, with most projects flourishing between the 10th and 13th centuries. These systems were so vital that they had dedicated administrators, like the 'dike chief,' responsible for their upkeep.
Japan's Ariake Sea in Kyushu and the reclaimed Lake Hachirōgata also feature significant polder developments, while South Korea's massive Saemangeum project represents one of the largest reclamation efforts in modern history.
European and North American Adaptations
Germany refers to its diked lands as 'koogs,' with an administrative system similar to the Dutch 'Deichgraf.' Interestingly, in southern Germany, 'polder' can also refer to retention basins used for river flood control—a slightly different, but still water-managing, application.
Across the Atlantic, polders are found in various forms. Canada's Tantramar Marshes and the Holland Marsh are prime examples, while in the United States, parts of New Orleans and the Sacramento–San Joaquin River Delta rely on extensive polder systems to remain dry and habitable.
The United Kingdom's Fens, Romney Marsh, and parts of the Severn Estuary also feature polder-like landscapes. From the Po River Delta in Italy to the Kuttanad region in India and even small pockets in France, Denmark, and Ireland, the polder stands as a global symbol of human tenacity against the forces of water.
Article
Polder
Aerial view of Flevopolder, the Netherlands
Satellite image of Noordoostpolder, the Netherlands (595.41 km2)
A polder (Dutch pronunciation: [ˈpɔldər] ) 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:
• Land reclaimed from a body of water, such as a lake or the seabed • Flood plains separated from the sea or river by a dike • Marshes separated from the surrounding water by a dike and subsequently drained; these are also known as koogs, especially in Germany
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 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 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 Imperial 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. 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
Polder
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.
Netherlands
Polder
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.
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 nationwide. By 1961, about half of the country's land, 18,000 square kilometres (6,800 sq mi), was reclaimed from the sea. About half the total surface area of polders in northwest 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.
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).
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 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.
Belgium
The Yser river and West Flemish polders near Diksmuide
• 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 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
• Filsø • Kolindsund • Lammefjorden
Finland
• Söderfjärden • Munsmo • Two polders (three square kilometres or 1.2 square miles in total) near Vassor in Korsholm
France
• Marais Poitevin • Les Moëres, adjacent to the Flemish polder De Moeren in Belgium. • Polders de Couesnon near Mont-Saint Michel in Normandy
Germany
Friedrichskoog is a polder in Schleswig-Holstein
Wesselburenerkoog
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.
• 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 term polder is used for retention basins recreated by opening dikes during river floodplain restoration, a meaning somewhat opposite to that in coastal context.
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
Netherlands
The meandering Stingsloot separates the Vrouw Vennepolder (left) and the Rode Polder (right)
Wind farms in the Noordoostpolder
Areas of the Netherlands located below sea level (blue)
• 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 • Krimpenerwaard • 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
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, adjacent 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