History of the dyke system in Bremen

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Wümmedeich, Niederblockland

The dyke system in Bremen includes the dykes on the Weser and its tributaries. Large parts of Bremen (approx. 85% of the urban area) are below the mean tidal high water level and are therefore at risk of flooding and storm tides . The embankment and maintenance, which began in the Middle Ages , is now the responsibility of the Bremischer Deichverband on the right bank of the Weser and the Bremischer Deichverband on the left bank of the Weser .

history

The beginnings

The Eisenradsdeich in 1781

In the 11th century the construction of Weser dykes began in the marshes around Bremen, but a planned dike was probably not carried out until the second half of the 12th century. Until then, the only protection of houses and settlements against floods was their construction on Wurten ( terps ) - heaped up mounds of earth - which, however, retained their importance and were constantly increased because the dykes did not offer sufficient protection during extreme floods and the winter flooding of the Arable land was even desired because of the fertilizing effect.

Dikes were built on the Weser as well as on its tributaries Ochtum , Lesum and Wümme . Their construction and maintenance could only be carried out in the community of villages and dike associations, who were subject to rules that were set by themselves or by the authorities: " If you don't want to think, have courage " ('If you don't want to dike, you have to give way'). There are also reports of harsh customs in enforcing this demand: Those who could not afford the money to repair the dike had to leave their home and yard. The dikemaster stuck a spade into the dike. The farmer who pulled it out took over the expropriated property at the same time as the duty to repair the dike.

The first construction of a dike mentioned in a document in Bremen dates from the year 1374, it was called "The old dike" until the 19th century.

Organizing in associations

Bremen around 1648 with dikes on the Weser, Ochtum and Lesum. (North right below)

In 1433 the important dike association of the four countries was established . He was responsible for the Lehester Deich, the Wümmedeiche downstream to Burg , the Eisenradsdeich (later part of the Osterdeich ) and other dykes above the city. There were other dike associations in the Gohen Vieland , Werder - and Hollerland , as well as in the Upper and Lower Blockland .

The cathedral chapter as well as the mayor and the Bremen council issued the right to die in the Bremischen veer Goden in 1449 , a contract on regulations and procedures for dike harbors and juries. A dyke count from the council, who was elected by the country folk, was at the head of a dyke association.

In 1473 a general dike order was laid down, which among other things said:

“Every owner of a piece of land behind the dyke is obliged to work and has to work on the dykes through manual and span services as well as monetary contributions. Everyone who works on the dyke has to make an honest change. No one is allowed to curse or make blasphemous speeches while the dike is being worked on. Nobody can evade the dyke obligations. "

Until 1598 the Gohgräfe des Vieland was also Deichgräfe, after that there were two Gohe, the Upper and Lower Vieland, each with a Goh- and Deichgräfen. The individual dyke sections were assigned to the peasant communities, with each farmer being assigned a stretch of dyke that he had to maintain; he was responsible for closing dike breaches with house and yard. In the event of major damage, the dike association stepped in.

Modern times

Weser dyke from the city moat to Oslebshausen 1805

On February 8, 1850, with the enactment of the new dyke regulations - the first dyke law in the modern sense - a dyke association was formed for the left and right sides of the Weser. Each was led by a senator and a building inspector, the dike jury and eight men were delegated from the individual villages. In addition to the two large dike associations, there were also smaller ones, such as the Lehester dyke association .

In 1876/78 the two dike associations were divided into two associations each, for which communion dykes were ordered. The four associations thus created were:

  • The dike association on the right bank of the Weser (responsible for the suburbs and rural areas protected by Weser, Lesum and Wümmedeiche dikes)
  • The dike association for Werderland (responsible for the area from the Oslebshauser dunes to Burg )
  • The dike association for the Niedervieland (responsible for the area from Woltmershausen to Hasenbüren )

Each of these dyke associations had a dike captain , a dike inspector, a dike rent master (accounting officer) and dyke sworn delegates who were delegated by the individual villages. Warf-Butendiek formed its own dike association with a dyke port.

20th century

In 1937, 27 independent associations formed the Bremische Deichverband on the right bank of the Weser . He was joined in 2004 by the Warf-Butendiek and Verenmoor associations.

In 1947 the Bremische Deichverband was founded on the left bank of the Weser . The dike associations of Neustadt, Obervielands, Niedervielands and Huchtings , which had been independent until then, merged into it, as well as another 23 dam and water associations.

In the 1990s, further dyke and flood protection tasks, which had previously been carried out by the Bremen Water Management Office , were transferred to the dyke associations.

Flood hazard

Gottfried Menken : Dike breach on Eisenradsdeich 1827

Even when the Bremen area was settled, people were aware of the danger of flooding, so they founded the city on the 26 km long dune that connected the two geest areas near Lesum in the north-west and Achim in the south-east. Where the city center is today, it led close to the banks of the Weser, so that it must have been possible to cross by ferry or ford .

The Bremen Cathedral , which was built at the highest point of the dune, and the old town surrounding it were spared from flooding . Frequent floods occurred in the Martini Church , built on the bellows island in 1229 , which could not be prevented even by building a defensive wall in 1371 and raising the floor in the church several times. This is also reflected in an old rhyme: “ Sunt Marten - wo de wind doer far; wo't Water döer geiht ”(Saint Martin - where the wind blows through; where the water goes through). The Johanniskirche in Schnoor shared the same fate when in 1823 the floor in the church was raised by three meters.

The catastrophic flood of 1881 once again proved how dangerous the winding course of the Weser and the sandbanks hindered the drainage of the water, and supported the plan of Bremen's chief construction director Ludwig Franzius to straighten the Lower Weser between the ports in Bremen and Bremerhaven , in order to create a higher one To achieve flow velocity. The correction had become necessary because the ports of Bremen had become inaccessible to large seagoing vessels due to the increasing siltation of the Weser.

A hundred years later, in March 1981, the breakthrough of the Weser near habenhausen caused one of the most severe floods of modern times in the state of Bremen. Melting snow in the low mountain ranges and rainfalls lasting for days in the Hameln area , combined with a defective weir in the Bremen Weser weir, led to rising water levels, which ultimately caused the dike to break.

Challenges of the future

In the brochure Flood Protection in the State of Bremen , the Senate reports in cooperation with the dike associations “on the flood protection situation in the State of Bremen and conclusions on the occasion of the flood disaster on the Elbe in August 2002”. It says: “The 'guidelines for future-oriented flood protection' from 1995 should then be technically reviewed and, if necessary, adjusted, taking into account the experiences of the summer floods in 2002. Based on the river basin, flood protection action plans are to be drawn up by the end of 2003, which contain binding measures for flood prevention and protection. ”Individual area-related flood protection plans and a general plan for coastal protection Lower Saxony / Bremen (2007) were then submitted.

This article or the following section is not adequately provided with supporting documents ( e.g. individual evidence ). Information without sufficient evidence could be removed soon. Please help Wikipedia by researching the information and including good evidence.

According to the latest study by the Intergovernmental Panel on Climate Change ( IPCC ), sea levels will rise faster than previously assumed over the next 100 years. Instead of the dyke heightening of 25 cm, which was previously considered necessary for Bremen, the dike association is now aiming for the one meter mark, according to its dike captain, with the provision for possible further increases. In addition to the financial outlay - the funds are to be raised by the federal government and the state - there are the technical challenges of raising the dike in the urban area. The historic 400-year-old sandstone wall on the Schlachte reaches 7.20 m above sea ​​level , eight meters are required here, and special precautions are also required in the area of ​​the Neustädter Hafen , where the dike offers the broad side of the river.

Due to the decades of expansion of the Weser, a tidal wave in the channel to Bremen takes two hours. The planned additional deepening of the Outer Weser could shorten this time. During a strong storm surge, the flood wave flows into the Weser at 40 to 45 km / h and could shorten the time to take precautions and close the flood gates to 90 minutes.

Individual evidence

  1. ↑ The Senator for Building and Environment: Flood Protection in the State of Bremen , p. 21.
  2. ^ General plan for coastal protection Lower Saxony / Bremen-Mainland. In: Coastal Protection Volume 1

literature

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