Flood control is an important issue for the Netherlands, as about two-thirds of its territory is vulnerable to flooding, while it is among the most densely populated on Earth. Natural dunes and built dykes, dams, and sluices provide defense against hurricanes from the ocean. The river dikes prevent flooding from water flowing into the country by the Rhine and Meuse major rivers, while the complicated system of drainage canals, canals, and pumping stations (historically: the windmill) keeps the dry lowland areas for shelter and agriculture. The water control board is an independent local government body responsible for maintaining this system.
In modern times, flood disasters coupled with technological developments have led to major construction work to reduce the influence of the ocean and prevent future floods.
Video Flood control in the Netherlands
Histori
Greek geographer, Pytheas, notes about the Low Country, when he passes them on the way to Heligoland around c. 325 BC, that "more people die in the struggle against water than in the struggle against men". The first-century Roman writer Pliny wrote something similar in his Natural History :
There, twice in every twenty-four hours, widespread ocean waves sweep floods over vast expanses of land and conceal the eternal controversy over whether this land belongs to land or sea. There these unfortunate people occupy a high ground, or a man-made platform built on the highest tide levels they experience; they live in huts built at the chosen location and like sailors on a ship when the water covers the surrounding land, but when the waves recede they are like a sunken victim. Around the hut they catch the fish as they try to escape with the ups and downs. It does not fall on their fate to raise cattle and live from milk, like neighboring tribes, or even to fight with wild animals, since shrubs have been pushed far back.
The area under threat of flooding in the Netherlands is essentially an alluvial plain, built from sediments abandoned by thousands of years flooded by rivers and seas. About 2,000 years ago most of the Dutch territory was covered by extensive peat swamps. Coastal consists of rows of coastal sand dunes and natural embankments that make the swamps do not leak but also carried by the sea. The only areas suitable for residence are in the higher elevations in the east and south and in the dunes and natural embankments along the coast and rivers. In some places, the sea has penetrated this natural defense and created a vast floodplain in the north. The first permanent inhabitants in this area may be attracted by a much more fertile soil clay deposited than deeper peat and sand lands inland. To protect themselves from floods, they build their homes in artificial hills called terpen or wierden (known as Warften or Halligen in Germany). Between 500 BC and AD 700 there may be periods of abode and neglect as the sea level periodically rises and falls. The first dike is a low embankment just one meter or higher around the field to protect the plant from occasional floods. Around the 9th century the sea was in the face again and many terps had to be raised to keep them safe. Many single terpes at this time grow together as a village. It's now connected to the first embankment.
After 1000 AD the population grows, which means there is greater demand for fertile land but there is also greater manpower available and the embankment construction is taken more seriously. The main contributors to the dike construction are the monasteries. As the largest land owners they have the organization, resources and manpower to undertake major construction. In 1250 most of the dikes were connected to sustainable sea defense.
The next step is to move more sea dikes. Each high and low tide cycle leaves a small layer of sediment. Over the years, these layers have reached such heights that rarely flood. It was considered safe to build new dikes around this area. The old dike is often kept as a secondary defense, called the sleeping embankment.
Embankment can not always be moved to the sea. Especially in the delta of the southwestern river, it is often the case that major sea dikes are damaged by tidal channels. Secondary dikes are then constructed, called inlaagdijk . With inland embankment, when the embankment toward the sea collapsed the secondary land dikes into the main one. Although redundancy provides security, the ground from the first embankment to the second is lost; over the years, losses can be significant.
Taking the soil from the flood cycle by putting a dike around it prevents it from being lifted by the mud left behind after the flood. At the same time the drained soil is consolidating and peat decomposes towards land subsidence. In this way the difference between the water level on one side and the level of land on the other side of the dike increases. While floods become more rare, if the embankment is overflowed or penetrated, the destruction is much greater.
The method of embankment construction has changed over the centuries. Popular in the Middle Ages was wierdijken , embankment ground with a seaweed protective coating. The clay dike is vertically cut on the side facing the sea. The seaweed is then stacked on this edge, held with a pole. The process of compression and decay results in a solid residue that proves to be very effective against wave action and they require very little maintenance. In places where seaweed is not available other materials such as reeds or rattan mats are used.
Another system that is used a lot and for a long time is a wooden vertical screen that is supported by the earth bank. Technically this vertical construction is less successful because the vibrations of the falling waves and leaching of the embankment foundation weaken the embankment.
Much of the damage occurring to this wooden construction with the advent of hookworm ( Teredo navalis ), the minds of bivalves had been brought to the Netherlands by the VOC merchant ship, which took its course through the Dutch sea defense in about 1730. The changes were made of wood to use stones for reinforcement. This is a major financial setback because there is no natural stone in the Netherlands and everything should be imported from abroad.
The dike is currently made with a sand core, covered by a thick layer of clay to produce waterproof and resistant to erosion. Levee without cape has a layer of rock that is destroyed beneath the surface of the water to slow the wave action. Up to high water levels, the embankment is often covered with carefully laid basalt or asphalt layers. The rest is covered with grass and kept by sheep grazing. Sheep keep the grass solid and solid the soil, unlike cattle.
Maps Flood control in the Netherlands
Develop a peat swamp
At about the same time as the embankment construction, the first swamp was made suitable for agriculture by the colonists. By digging a parallel drainage ditch system dried from the ground to grow grain. However, peat is more than any other soil type when it is dried and soil degradation causes the developing area to become wet again. Cultivated land that was originally used to grow grains became too wet and switched to dairy farms. A new area behind the existing fields is then cultivated, heading deeper into the wild. This cycle repeats several times until different developments meet each other and no more undeveloped land is available. All the land is then used for cattle grazing.
Due to the continuous depletion of the soil, it is increasingly difficult to remove excess water. The mouths of rivers and streams are dammed to prevent high water levels from flowing back upstream and overflowing cultivated land. This dam has a wooden culvert equipped with a valve, which allows drainage but prevents water from flowing upstream. This dam, however, blocked the delivery and economic activity caused by the need to move goods causing the village to grow near the dam, some notable examples being Amsterdam (dam on the Amstel river) and Rotterdam (dam in Rotte). Only in the later centuries was built the key to allowing the ship to pass.
Further drainage can only be done after the development of windmills polder in the 15th century. The wind-driven water pump has become one of the tourist attractions of the Dutch trademark. The first drainage plant using spoon wheel can increase water at most 1.5 m. By combining the plant, the height of pumping can be improved. Then the factory is equipped with Archimedes screws that can increase the water much higher. Polders, now often below sea level, remain dry with mills pumping water from pit ditches and canals to boezem ("chest"), canals and lakes systems connecting different polders and acts as storage to water can be released into the river or sea, either by a sluice at low tide or using a pump further. The system is still in use today, although the drainage plant has been replaced by the first steam and then the diesel and electric pump stations.
The growth of cities and industry in the Middle Ages resulted in an increase in the demand for dry peat as a fuel. First, all the peat to the ground water table was dug. In the 16th century, a method was developed to dig underwater peat, using dredging nets on long poles. Large scale peat dredging is taken by the company, supported by investors from the cities. These efforts often destroy the landscape when the agricultural land is dug and the remaining back, used to drain peat, collapses under the action of the waves. Small lakes are created that quickly grow in the area, any increase in surface water causes more wind influence in the water to attack more land. Even caused the villages lost to the man-made lake waves. The development of a polder factory gives the option to dry the lake. In the 16th century, this work began in shallow, small lakes, continuing with larger and deeper lakes, though it was not until the nineteenth century that the most dangerous lake, the Haarlemmermeer near Amsterdam, was dried by steam power.. Dried lakes and new polders can often be easily distinguished on topographic maps by their different regular pattern of distribution compared to their older neighborhoods. Millwright and hydraulic engineer Jan Leeghwater have become famous for his involvement in these works.
River flood control
The three great rivers of Europe, the Rhine, the Meuse, and Scheldt flow through the Netherlands, where the Rhine and Meuse cross the country from east to west.
The first major construction work on the river was done by the Romans. Nero Claudius Drusus was responsible for building a dam on the Rhine to divert water from the branch of the Waal river to Nederrijn and possibly to connect the river IJssel, formerly only a small river, to the Rhine. Whether this is intended as a flood control measure or only for military defense and transportation purposes is unclear.
The first river dikes emerged near the mouth of the river in the 11th century, where attacks from the sea increased the danger of water levels in the river. Local authorities block the river branches to prevent flooding in their lands (Graaf van Holland, ca. 1160, Kromme Rijn; Floris V, 1285, Hollandse IJssel), only cause problems for others living upriver further. Large-scale deforestation in the upstream causes river levels to become more extreme while fertile land demand causes more land to be protected by embankments, giving less room to the river basin and causing higher water levels. Local dikes to protect villages are linked to make a banning embankment to accommodate the river at all times. These developments mean that while the usual floods for the first inhabitants of the river valleys are just a nuisance, on the contrary the occasional floods occur when the dikes burst far more destructively.
The 17th-18th century was a period of the famous river flood that caused many fatalities. They are often caused by ice dams that block the river. The work of land reclamation, large willow plantations and buildings in the winter base of the river deteriorated the problem. In addition to clear cleaning of winter beds, overlays ( overlaten ) were created. This is a deliberately low dike where excess water can be diverted downstream. Land in such diversionary channels is guarded from buildings and obstructions. Since this so-called green river is therefore basically only used for livestock grazing, the following centuries are seen as wasteful land use. Most of the overflow has now been removed, focusing on stronger dikes and more control over water distribution across branches. To reach this channel like Pannerdens Kanaal and Nieuwe Merwede excavated.
A committee reported in 1977 about the weakness of the river dike, but there was too much resistance from the local population against the houses that destroyed and straightened and strengthened the tortuous old dikes. It took flood threats in 1993 and again in 1995, when more than 200,000 people had to be evacuated and the newly held embankment, to implement the plan. Now the risk of river flooding has been reduced from once every 100 years to once every 1,250 years. Further work in the Room for the River project is being done to give the river more room to flood and in this way reduce the height of the flood.
Water control board
The first dikes and water control structures are built and maintained by those who directly benefit from them, mostly farmers. Due to the wider structure and complex councils formed from people with similar interests in controlling water levels in their soil, the first water council began to emerge. These are often controlled only in small areas, polders or single embankments. Then they join or the whole organization is formed when different water boards have conflicting interests. Original water boards are very different from each other in the organization, power, and area they manage. The differences are often regional and dictated by different circumstances, whether they should maintain a sea dike against storm surges or keep the water level within the polder within limits. In the mid-20th century there were about 2,700 water control boards. After many mergers, there are currently 27 water boards remaining. Water councils hold separate elections, levy taxes, and function independently from other government agencies.
The dikes are managed by individuals who benefit from their existence, each farmer has been designated as part of the dike to be maintained, with a three-year observation by the water board director. The old rule of "Water who is sick, he water stops" ( Wie het water deert, die het water keert ) means that those living on the embankment must pay and take care of it. This leads to haphazard maintenance and it is believed that many floods will not occur or will not become severe if the dikes are in better condition. Those who live in rural areas more often refuse to pay or assist in the maintenance of the dikes even if they are also affected by floods, while those living on the embankment themselves can go bankrupt by having to repair damaged levees.
Rijkswaterstaat (Directorate General of Public Works and Water Management) was established in 1798 under French rule to place water controls in the Netherlands under the central government. However, local waterboards are too tied to their autonomy and for most of the time Rijkswaterstaat works beside the local waterboards. Rijkswaterstaat has been responsible for many major water control structures and then and still is involved in building railroads and highways.
The water board can try new experiments like sand machines off the North Holland coast.
Famous flood
Over the years there have been many storm surges and floods in the Netherlands. Some people deserve special mention because they have changed the contours of the Netherlands.
A series of devastating storm surges, beginning with the First All Saints ( Allerheiligenvloed) in 1170 which swept through a large area of ​​peat swamps, enlarging the Wadden Sea and connecting the former Almere Lakes. in the middle of the country to the North Sea, thus creating Zuiderzee. That alone would cause many problems until Afsluitdijk's development in 1933.
Several storms began in 1219 creating Dollart from the mouth of the river Ems. By 1520, Dollart had reached its largest area. Reiderland, which contains several towns and villages, is missing. Much of this land was later reclaimed.
In 1421, the flood of St. Elizabeth led to the loss of De Grote Waard in the southwest of the country. Particularly the excavation of peat near the embankment for salt production and neglect due to the civil war caused the failed levee, which created Biesbosch, now a precious preserve.
The more recent floods of 1916 and 1953 gave rise to the construction of Afsluitdijk and Deltaworks respectively.
Flood as a military defense
By deliberately flooding certain areas, military defense lines can be created. In the case of an advanced enemy army, the area was flooded with about 30 cm (1 ft) of water, too shallow for the vessel but deep enough to make walking legs difficult, hide obstacles underwater like canals, trenches, and built with purpose. trap. The embankment that crosses flood areas and other strategic points is protected by a stronghold. The system proved successful in the Hollandic Water Line in the 1672 rampjaar during the Third Dutch-British War but was overcome in 1795 due to severe frozen weather. It was also used with Stelling van Amsterdam, the Grebbe line and the IJssel Line. The appearance of heavier artillery and especially airplanes makes this strategy very obsolete.
Modern developments
The development of technology in the 20th century meant that larger projects could be undertaken to further improve the security of floods and to reclaim large areas of land. The most important is the Zuiderzee Works and Delta Works. By the end of the twentieth century all the seawalls had been sealed off the sea by dams and barriers. Only Westerschelde need to stay open for access to ports of Antwerp. Plans to reclaim parts of the Sea of ​​Wadden and Markermeer were eventually canceled due to the ecological and recreational values ​​of these waters.
Zuiderzee Works
The Zuiderzee Works (Zuiderzeewerken) is a system of dams, land reclamation, and water drainage. The basis of this project is the demolition of Zuiderzee, a large shallow inlet of the North Sea. This dam, called Afsluitdijk, was built in 1932-33, separating Zuiderzee from the North Sea. As a result, Zuider sea becomes IJsselmeer - IJssel lake.
Following the dam, most of the land is reclaimed in the body of a freshwater lake by using polders. These works were carried out in several steps from 1920 to 1975. Engineer Cornelis Lely played a major part in his design and as a statesman in authorizing his development.
Delta Works
A study conducted by Rijkswaterstaat in 1937 showed that sea defense in the southwest river delta was inadequate to withstand a major storm surge. The proposed solution is to stem all river mouths and inlets that shorten the shore. However, because of the scale of this project and the intervention of the Second World War the construction was delayed and the first work was only completed in 1950. The 1953 North Sea flood provided a major boost to accelerate the project. In subsequent years a number of dams were built to close estuarine estuaries. In 1976, under pressure from environmental groups and the fishing industry, it was decided not to close the estuary of Oosterschelde with a dense dam but instead to build Oosterscheldekering, a storm-wave barrier that was only closed during a storm. This is the most famous (and most expensive) project dam. The second major hurdle for the job is in the Rijnmond area. A storm surge through Nieuwe Waterweg will threaten about 1.5 million people around Rotterdam. However, closing the mouth of this river will be very detrimental to the Dutch economy, because the Port of Rotterdam - one of the largest sea ports in the world - uses the mouth of this river. Finally, Maeslantkering was built in 1997, taking into account the economical factor: Maeslantkering is a collection of two swinging doors that can cover the mouth of the river when needed, but usually open. The Maeslantkering is expected to be closed about once per decade. Until January 2012, it has been closed only once, in 2007. The project was completed with the construction of Maeslantkering in 1997.
The current situation and the future
The current sea defenses are stronger than ever, but experts warn that self-satisfaction will be a mistake. The new calculation method reveals many weak points. Sea level rise can increase the average sea level by one to two meters by the end of this century, with many more following. This, the decline of the land, and the increase in storms make further improvements to the flood control and water management infrastructure required.
Marine defense continues to be strengthened and raised to meet the safety norms of the possibility of flood once every 10,000 years to the west, which is the heart of the economy and the most populous parts of the Netherlands, and once every 4000 years for a less populated population. area. Primary flood defenses are tested against this norm every five years. In 2010 about 800 km of total 3,500 km failed to meet the norm. This does not mean there is a risk of direct flooding; it is the result of the norm becoming more stringent than the results of scientific research on, for example, wave action and sea level rise.
The amount of coastal erosion compared to the so-called "baseline shoreline" ( BasisKustLijn ), the average coastline in 1990. The sand filling is used when the coast has retreated too far. Approximately 12 million m 3 sand is stored annually on the beach and below the water line in front of the beach.
Stormvloedwaarschuwingsdienst (SVSD: Storm Surge Warning Service) makes estimates of water levels in case of storm surges and warns responsible parties in the affected coastal areas. These can then take appropriate measures depending on expected water levels, such as evacuating areas outside the embankment, closing obstacles and in extreme cases patrolling the embankment during a storm.
The second Delta Committee, or the Veerman Committee, officially Staatscommissie voor Duurzame Kustontwikkeling (State Committee for Longshore Coastal Development) advises in 2008. It is estimated that sea level rise is 65-130 cm by 2100. Among his suggestions are:
- to increase the tenfold security norm and strengthen the appropriate embankment,
- to use sand filling to expand the North Sea coast and allow it to grow naturally,
- using lakes in the southwest river delta as river basins,
- to raise the water level in IJsselmeer to provide clean water.
These measures will cost around 1 billion Euro/year.
Space for the River
Global warming in the 21st century could lead to an increase in sea level that could weigh on the actions taken by the Netherlands to control floods. The Room for the River project allows for periodic flooding in unsustainable land. In such areas the population has been moved to higher ground, some of which have been raised above the anticipated flood levels.
References
- Vergemissen, H (1998). "Het woelige water; Watermanagment in Nederland", Teleac/NOT, ISBN 90-6533-467-X
- Ten Brinke, W (2007). "Land in Zee; De watergeschiedenis van Nederland", Veen Magazine, ISBN 978-90-8571-073-8
- Stol, T (1993). "Wassend water, dalend land; Geschiedenis van Nederland en het water", Kosmos, ISBN 90-215-2183-0
External links
- DeltaWorks.org - the 1953 flooding website and the construction of Delta Works
- Water Management in the Netherlands - the 2009 publication by the Dutch Ministry of Infrastructure and Environment: Rijkswaterstaat
- FloodControl2015.com - Research program 2008-2012 for flood control in the Netherlands
Source of the article : Wikipedia
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