Land reclamation

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Land reclamation near Hedwigenkoog , Dithmarschen
Land reclamation on Eiderstedt
Land reclamation on Eiderstedt
Land reclamation on Eiderstedt
Polder stairs on a former dike of the Jadebusen : The areas on the left diked in 1593/94 are lower than the Alte Wapeler Groden diked in 1733 on the right.

Land reclamation or new land reclamation comprises various measures for the development of new land, especially from the sea and water. In the German Bight , the term traditionally stands primarily for the artificial acceleration of the silting process at suitable points on coasts in the Wadden Sea . The word is also used for the backfilling of large areas in coastal areas, e.g. B. by means of suction dredgers, the drainage of areas by embankment (and subsequent, possibly permanent, pumping out) and generally used for the reclamation of previously unused areas.

Land reclamation by tipping

In the North Sea region, a system of groynes and parapets is often created for land reclamation in order to calm the water and to delay the run -off of the suspended particles carried along in the water at low tide . In calm water, these settle on the sea ​​floor as sediments or silt .

The flood transports sand, silt, clay, organic matter and other things as suspended matter . During the rest phase of the water during the tide change, this material settles as silt between the groynes and fences as well as in the basins that are surrounded by them, the seabed gradually rises. Pioneer plants such as the salt-tolerant samphire or beach grass can settle and bind sediments.

When the sea floor reaches the tide level, trenches are dug and the silt that is dug out is spread over the land to increase it further. New sediments can now be deposited in the trenches. The land gained in this way is mostly in front of the protective dike and is therefore referred to as the foreland . As such, it also serves to protect the dike by braking the tidal waves approaching the dike.

If the foreland is large enough and is to be used permanently, it is protected from storm surges with dykes . The diked land is called Koog ( Schleswig-Holstein ), Groden ( Oldenburg ) or Polder ( Netherlands , East Frisia ) , depending on the region . Only the dike enables complete desalination of the soil in the long term. This happens through precipitation, which flushes out the salt present in the soil. As a rule, this rainwater is collected in weather and drained off through sewers , which at the same time prevent the re-penetration of salt water . Usually, the foreland was considered ripe for embankment when the white clover blooms there, as this species tolerates a salt content similar to that of agricultural crops.

As dikes have been increasingly prepared by means of depositing measures, polder stairs have been created in some marsh countries. There, the areas that were later diked are higher than those that were diked earlier.

In Germany around 180 kegs or polders have been won so far. In some dike projects such as the Hauke-Haien-Koog , the Koogland was not used for agriculture, but as a bird sanctuary .

Land reclamation through damming

In the Netherlands - in connection with coastal protection - after the damming of the IJsselmeer, another form of land reclamation was practiced by first building the dikes in the area dammed by the sea and then the newly delimited polders, first with wind pumps , and later with them pumped empty using steam or motorized pumps. The classic, time-consuming and costly new land reclamation by sedimentation was not used here, so the soil is still consistently below sea level (= depression). The disadvantage of this approach is that the precipitation has to be pumped out permanently. In some cases, the procedure was also used elsewhere (e.g. when building the storage area in the Meldorfer Bucht ) when land reclamation through sedimentation had not progressed as far as desired.

Land reclamation by backfill

In individual cases, however, land is also gained through massive embankment of sand or stones, e.g. B. for coastal protection or to gain building ground. In Singapore , 135 square kilometers , in Tokyo even 249 square kilometers of land were heaped up and secured, and in Japan they are known as Umetate chi . In Germany, for example, 360  hectares of land were removed for the construction of the JadeWeserPort near Wilhelmshaven . A similar approach is also being pursued in the Maldives , also in order to resist the rise of the seas. The airport island of Hulhulé and the neighboring island of Hulhumalé were enlarged through land reclamation. Such major earthwork projects have only been technically possible for a few years.

Social discussion

The benefits of land reclamation are controversial. On the one hand, it should serve to protect the coast by placing kegs in front of populated areas, on the other hand, land reclamation will destroy valuable ecosystems such as the mudflats and salt marshes .

In Germany, the Neufelder Koog was last established in 1923/24 for purely commercial reasons (financed from private sources). Newer kings like the Hauke-Haien-Koog from 1958 to 1960 deliberately include large bird sanctuaries. The last major dike in Germany was the construction of the Beltringharder Kooges (dike closure 1987) with an area of ​​3350 ha, which today represents the largest nature reserve on the Schleswig-Holstein mainland.

Variation in meaning: Reclamation of previously unused areas

The reclamation of new land is also used to describe the reclamation of arable land , i.e. the reclamation of agriculturally unused wilderness. The Neuland campaigns (Russian: zelina ) in the former Soviet Union in black earth areas of southern Siberia , Kazakhstan , Uzbekistan and Turkmenistan in the 1920s , 1930s and 1950s are well known  . This large-scale reclamation of land was mostly associated with the creation of protective forest strips against wind erosion and in some cases with the creation of large irrigation systems. The hoped-for increase in the yield of agricultural products ( wheat , cotton ) mostly did not materialize in the long run, and massive ecological problems arose, for example on the Aral Sea .

But also the reclamation of land in the Ukraine , southern Russia , the Midwest of the USA , Argentina , parts of Africa or Australia between the 18th and 20th centuries followed similar principles.

Web links

Commons : Land Reclamation  - Collection of images, videos and audio files
Wiktionary: Land reclamation  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ^ Karl-Ernst Behre : History of the landscape around the Jade Bay . Wilhelmshaven 2012, ISBN 978-3-941929-02-9 , pp. 136-148.
  2. ( Memento from September 28, 2007 in the Internet Archive ) JadeWeserPort Realisierungs-Beteiligungsgesellschaft mbH