The Marsdiep is a deep tide race between Den Helder and Texel in the Netherlands, and running southwards between sandbanks. That gap connects the North Sea and the Waddenzee .
25-572: Around 1000 AD and before, much of the modern Waddenzee and IJsselmeer was land and the Marsdiep was an ordinary brook. An early form of its name is Maresdeop, a name probably related to modern Dutch moerasdiep ("swamp deep"). During the All Saints' Flood of 1170 , the sea broke through the original dune barrier and created the channel. The Marsdiep was in the age of sail in English called
50-647: A dyke was built between Enkhuizen and Lelystad as the northern boundary of the Markerwaard , a planned but never realized polder in the IJsselmeer. This dyke, the Houtribdijk or Markerwaarddijk , split the IJsselmeer into two parts. The former southern part of the IJsselmeer is now the hydrologically separate Markermeer . The proposed polderisation of the Markerwaard was abandoned after many of
75-656: A major hydraulic engineering project that involved building dykes, draining parts of the Zuiderzee, and constructing the Afsluitdijk to keep tides and high water out. In 1932 the Zuiderzee was closed off by the Afsluitdijk, a 32-kilometre (20 mi) dyke connecting Friesland and North Holland on either side of the Zuiderzee. The Zuiderzee was no longer a sea inlet and was renamed IJsselmeer ( Lake IJssel ) after
100-421: 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
125-407: 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
150-608: 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) Several cities on
175-556: The IJssel river that flows into it, which is also the namesake of the province of Overijssel . The continuing flow of fresh river water soon flushed out the salt water. Part of the IJsselmeer was later closed off to form the Markermeer . From 1929 till 1967, over half the IJsselmeer was drained, creating 1,979 km (764 sq mi) of polders : Wieringermeerpolder , Noordoostpolder , East and South Flevoland . In 1975,
200-786: 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 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. The Jiangnan region, at
225-471: The Texel, in distinction from the island of Texel. This North Holland location article is a stub . You can help Misplaced Pages by expanding it . IJsselmeer The IJsselmeer ( Dutch: [ˌɛisəlˈmeːr] ; West Frisian : Iselmar , Dutch Low Saxon : Iesselmeer ), also known as Lake IJssel in English, is a closed-off freshwater lake in the central Netherlands bordering
250-486: 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
275-424: The provinces of Flevoland , North Holland and Friesland . It covers an area of 1,100 km (420 sq mi) with an average depth of 4.5 m (15 ft). The river IJssel , after which the lake was named, flows into the IJsselmeer. Two thousand years ago Pomponius Mela , a Roman geographer, mentioned a complex of lakes at the current location of the IJsselmeer. He called it Lacus Flevo . Over
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#1732773236852300-542: 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
325-558: The Dutch population did not want the loss of the traditional seaside (now lakeside) environment and vistas. In 1986 three polders in the IJsselmeer constituted the new province of Flevoland , the twelfth province of the Netherlands. The water of the IJsselmeer is now almost completely fresh, the saline having long since been purged. This altered environment has had an impact on the fish and plant ecosystems . The change has been beneficial for Dutch boats, many of which are steel, as
350-471: The English Channel, creating very high tides along the Dutch coast. During the 17th century, Zuiderzee dykes collapsed several times, and plans were drawn up to eliminate the threat by draining the bay. Later drainage plans focused on creating fertile farmland, but they never progressed beyond the planning stage. It was only after the flood of 1916 that the legislature approved the Zuiderzee Works ,
375-413: The IJsselmeer, the closed-off bay functions as a large freshwater reservoir, serving as a source for agriculture and drinking water. Outlet sluices in the Afsluitdijk regulate the water level of the IJsselmeer. The IJsselmeer is used for transport and fishing. It also offers a number of opportunities for recreational activity, both on the water and on its shores. Due to the shallowness of the IJsselmeer,
400-673: The Markermeer, and the bordering lakes , its cities and fishing villages remained mostly unspoilt and have many historic buildings. The IJsselmeer is home to the offshore segments of Windpark Noordoostpolder . In the future, Windpark Fryslan will also be built in this bay. Polder 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: The ground level in drained marshes subsides over time. All polders will eventually be below
425-428: 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
450-572: The centuries, the lake banks crumbled away due to flooding and wave action, and the lake, now called the Almere , grew considerably. During the 12th and 13th centuries, storm surges and rising sea levels flooded large areas of land between the lake and the North Sea, turning the lake into a bay of the North Sea, called the Zuiderzee . The Zuiderzee continued to be a threat to the Dutch, especially when northwesterly storms funnel North Sea waters towards
475-486: The freshwater significantly reduces rusting of the hulls, and there is far less build-up of marine growth (such as algae and barnacles below the barges ' waterlines). This has the knock-on benefit that barges and yachts in the IJsselmeer need far less antifouling , a coating which is inevitably somewhat toxic to wildlife. Due to considerable amounts of water from the Rhine flowing through its distributary IJssel into
500-551: 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 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 . In southern Germany, the term polder is used for retention basins recreated by opening dikes during river floodplain restoration ,
525-485: 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
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#1732773236852550-799: 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 . The Dutch word polder derives successively from Middle Dutch polre , from Old Dutch polra , and ultimately from pol- ,
575-569: 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
600-543: 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
625-594: 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
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