History of coastal protection on the North Sea coast

The history of coastal protection on the North Sea coast goes through various epochal phases. It begins with the construction of the first dikes in the Middle Ages and has continued to develop up to the present day. So that a uniform protection could be guaranteed in the long term, the dyke law was created from independent associations of the affected regions, in which standards and specifications for construction and maintenance are given and which still exists in a modified form today. The German North Sea coast is very susceptible to storm surges due to its morphological nature . Over the past centuries, people have developed coastal protection techniques, including building dikes in particular . As a result, artificial coastlines could be established anthropogenic and, which was particularly relevant on the North Sea coast, new territory could be gained. The development of the technical as well as the social and legal aspects of dyke construction can be traced from the Middle Ages to the present day using writings and the coastal landscape itself.

Dyke construction has always been a topical issue in the various periods of time, but with a changing character. Depending on the social characteristics of the time, the technology of dyke construction changed, as did the law on dykes and related goals. So the reclamation of new land has now moved into the background, in favor of ecological and sustainable goals.

Due to the onset of climate change , which brings about a rise in sea levels or an increase in extreme events, coastal protection is currently becoming extremely relevant. Without the dyke construction, an area of ​​more than 3,400 square kilometers on the German North Sea coast could be flooded.

The history of dyke construction on the German North Sea coast

The development of dyke construction is shown here based on the Middle Ages , the early modern period and since the 20th century. Influencing factors such as the law on dikes and storm surges are used and progress in construction and coastal protection is explained.

Historical background

The coast on the North Sea is naturally very flat, which is why the mainland was often flooded before the dyke began to be built. In addition, there were a large number of Halligen and islands in today's mainland. But as early as the Middle Ages, people tried to protect themselves from floods and devastating storm surges - the Julian and Marcellus floods , for example, killed several thousand people. At the same time, the land should be made arable . Within the scope of the possibilities at that time, the settlements mostly took place on hills and elevations. In the further course also on artificially constructed hills, the so-called terps . These terps only protected individual farms or village settlements and not the surrounding pastures and arable land, which threatened agricultural yields. Nevertheless, they remained the only effective flood protection until the dyke was built at the end of the first millennium ; because until the beginning of the Middle Ages, the coastal inhabitants of the North Sea did not know the form of dyke construction.

Dike construction in the Middle Ages

The aim of the dyke construction at that time was basically to secure the arable land and, above all, the harvest yields from storm surges, as the settlements were already protected by the terps or mounds.

Information about the exact start of the dike construction can only be guessed at from written records and archaeological excavations. The Frisians, who colonized large parts of the south-west coast between the 8th and 11th centuries, were largely responsible for building the dyke. In the oldest Frisian law, the so-called "Lex Frisionum" (from the years 802/803), dyke construction was not yet mentioned. According to archaeological excavations, the construction of the dyke began as early as the 8th and 9th centuries. The beginning of the dike construction on the North Sea coast is dated to the 11th and 12th centuries. From the 11th century onwards, dyke construction was favored by the sinking sea level and the rarer flooding. The march was also able to build up due to the prolonged dry season in the mudflats. Because the sea level was rising again, the construction of a dike had become indispensable for the population if the fertile marshland was to be used for grazing and cultivation in the future.

Systems and profiles in dyke construction

A ring dike system near Wartha

The first dykes built were so-called ring dikes . These inland summer dykes were low earth walls, not particularly wide, characterized by steep embankments and mostly only between 1.20 meters and a maximum of 2.80 meters high. They surrounded both agricultural land and settlement areas and were intended to protect the soil from flooding and salinisation, especially in summer, which enabled the cultivation of grain, especially oats and horse beans, as well as cattle breeding. The dikes, which were also intended for storm surges in the summer months, functioned in a similar way.

In the past, a wide foreland was a prerequisite for the long-term existence of the dykes. The course and the width of the dike were determined by so-called 'sticks'. These are wooden stakes that were driven into the ground and were intended to delimit the area. Often, in the first years of construction, summer dykes were built, which could not withstand the floods in winter and consequently the marshes were also flooded. If one wanted to protect the landscape all year round, new dikes were necessary. It was not until the late Middle Ages that winter dykes , which also resisted high storm surges, were built as additional protective functions , mostly parallel to the coast .

Initially, the dike line on the North Sea coast was irregular. It was based on the bays, the nature of the material that was necessary for the construction of the dyke, and the dike breaches, so that the dyke line often had to be moved back. Overall, more land was lost than could be gained through diked polders . The cultivation of the Sietland , which was drained and diked, followed only in small steps . The settlements were gradually connected with each other by means of connecting dikes, whose three to four meter wide dike crests also served as traffic routes. Gradually, by connecting the dykes, a continuous dyke line was created directly on the Frisian North Sea coast. Historical sources show that this was largely closed as early as the 12th century. The so-called Golden Ring was completed by the end of the 13th century, which closed the dike line and thus established the separation between the sea and the East Frisian land. This dyke system should henceforth enable the settlement and cultivation of deep-lying and moored Sietländer in the hinterland of the marshland to the Geestrand and at the same time protect the coastal inhabitants and their lands from floods and storm surges throughout the year. However, due to their nature, they could not withstand all storm surges and dike breaches often occurred, which had fatal consequences for the residents behind the dike.

Dike work and building materials

Representation of the dike construction in earlier times

For the construction of the dikes and the necessary earthworks, the population at that time only had human labor available. In connection with spades, shovels and (horse) carts, an enormous effort was necessary to build dikes without mechanical help. Thus, the extraction of suitable dyke soil determined the location of a new dike to be built, as long transport without adequate vehicles was unthinkable at the time. The dyke soil differed in their composition. A distinction was made between marine, more sandy, fluvial or more clayey sediments. The building material consisted of various clay and fine sand fractions and was as Klei referred. In order to make the dyke body resistant to storm tides, it was covered with a layer of grass, so-called turf.

The clay must not contain too much clay, otherwise it will shrink when it dries out and cracks appear through which water can penetrate. If the clay has too much sand, it is also permeable to water. Clay which was mixed in with sand turned out to be the most suitable.

First of all, the material for the required dyke floor was dug up near the foot of the dyke, creating a depression that minimized the stability of the dyke and destabilized it. This is why the distance to the dike foot has been increased over time. The building material was preferably removed from outside the dike in order not to lose any land for agricultural use.

In order to prevent the foreland from being washed out, rules had to be followed. The excavation of the dyke soil required that no channel-like gullies were created. After the completion of the outer slope, the dyke body was covered with turf and then compacted by pounding people or horses.

The height of the dike has been determined by the highest known storm surge to date. However, the dyke heights did not take into account the rise in the water level, which led to several subsequent storm surge disasters. There was also no uniform conception of the cross-sectional design of the dikes until the 18th century. There were many dykes whose outer slope was too steep. In addition, there was simply a lack of knowledge about robust dike profiles, as well as building instructions or dyke builders. Also at that time there were no building regulations or service instructions, so that dyke construction could only be established in the 16th century. Until the 18th century, when there were dike builders, nothing changed in the profile design of the dikes.

Protection of the dike foot and embankment

If the foot of the dyke was directly adjacent to the tidal flats due to the surf or currents, measures are required to protect the so-called Schardeich from storm tides.

Example of a stack dike in North Friesland

The dyke was "embroidered" with straw, which meant that precipitation could run off better and the dyke was protected from water movements during the tides. The method of sticking straw goes back to the 14th century and is considered to be very expensive. As an alternative to straw, thatch was also used. If there was a lack of thatch and straw, a very durable protective layer was used, which was covered with so-called 'hurdles'. These in turn consisted of willow and hazel branches that were intertwined.

An alternative was the construction of stack dikes . These are vertical pile walls that form the base of the dyke and are anchored in the actual dyke body. This approach is unsuitable from a hydraulic point of view, as it leads to the construction being undermined and the safety of the dike at risk.

Changes and consequences of the dike construction

The construction of the dyke changed the economic and social structure on the coast at that time. The extensive pasture management was replaced by intensive agriculture and cattle farming. In the previously not yet diked march, woolen sheep were kept, which were the basis for the Frisian cloth production.

The first dikes were built around the fields to protect crops. The cultivation of grain was favored by the young deposits from the North Sea on sandy marches. The river marshes are more difficult to cultivate due to their high proportion of clay and were therefore used for livestock farming.

A prerequisite for agricultural use was a deeper drainage than in the previous pasture land, which resulted in a subsidence in the marsh. In addition to arable farming, peat was mined in diked areas, on the one hand for salt peat extraction and on the other hand for burning purposes. Despite falling water levels in the North Sea, the land use resulted in parts of the land lying below the mean high tide. This made it particularly susceptible to storm surges, which could reach far inland, causing the people in the Middle Ages to record massive land losses.

By closing the dyke line in the 13th century, the marshland was secured against storm surges. As a result, the storm tides built up correspondingly higher in front of the dikes and the dike often broke. The artificial drainage associated with the construction of the dyke led to the subsidence of the Sietland areas. If the water masses penetrated deeper areas, they often stayed there and formed a bay. If the ingress was not closed in a timely manner, subsequent storm surges could enlarge the bay by removing slightly eroded peat . Since the formation of the Golden Ring in the 13th century, the Dollart , the Leybucht , the North Frisian Wadden Sea and the Jade Bay have emerged . The first ingression was probably caused by the First Marcellus Flood in 1219. The Second Marcellus Flood of 1362 also had significant consequences in addition to the loss of huge marshland areas. At the political level, the Frisian district of Rüstringen was initially divided into two parts and then completely smashed. The loss of land in the following 300 years is entirely due to human activity.

Dyke law in the Middle Ages

Drawing of the dike construction from the Sachsenspiegel

In Friesland, thanks to the Frisian Freedom, the Frisians were not subject to any state aristocracy and lived autonomously. However, due to the necessity of building the dike, an overarching planning was necessary. From then on, the Frisians joined together as a cooperative in autonomous municipalities in order to take care of the dike in Friesland and to contain the dangers of the sea. This cooperative task was mandatory for everyone, regardless of gender, age or status.

After Denmark's defeat in the Battle of Hemmingstedt in the 15th century, the so-called Dithmarschen peasant republic consolidated its unofficial independence, so that self-government developed in the Dithmarschen region . Compared to the autonomous Frisians, Dithmarschen was a Saxon area. The Saxon gender associations were responsible for planning the construction of the dike.

Basically, all the march farmers were united in the farming cooperatives. They were responsible for the construction and maintenance of the dikes. According to the motto “If you don't want to dike, you have to give way”, participation in the construction of the dyke was mandatory, the so-called dyke service obligation . Since each coastal region was subject to a different administration, there were differences from region to region and no uniformly valid laws. Generally applicable dike rights were first recorded by the various regional municipalities at the time of supra-regional dyke construction, so that further examples of medieval-early modern regulations can be cited.

Instructions regarding the law on dikes can be found in both the Rüstringen legal manuscript (approx. 1300) and the Sachsenspiegel (1336). The Rüstringen legal handwriting speaks, for example, "of the maintenance of the Frisian golden relief - a picturesque paraphrase of the sea dike."

In the Sachsenspiegel, villages on the water are obliged to protect themselves against the floods and to build dams. Failure to participate in the construction of the dike would result in the loss of his land. As a result, according to the law of spaten , someone lost his property and relinquished the associated duties. For this purpose, a spade was stuck into the property as a sign of abandonment or as a sign of expropriation. Whoever pulled out this spade took over ownership and duties at the same time. This Spadelandsrecht (1424) regulated the law of dikes in the various marsh regions for almost 300 years until it was last applied around 1700.

Likewise, areas could only be acquired or inherited in combination with the dyke section. “No dike without a land, no land without a dike.” Until the introduction of land rights in the 15th century, parishes or the upper class of large farmers were responsible, among other things, for jurisdiction and dyke construction.

Dyke construction in the early modern period

Dike construction in earlier times, drawing by Gustav Schönleber around 1875

Contemporary depiction of the Burchardi flood

The expansion and improvement of the dikes proceeded very slowly in the early modern period . There was still the belief that God wanted to punish people with the floods and that there could not be a dike that could protect against God's wrath. Only over time did people realize that the broken dykes should be built higher and stronger when building new ones.

Storm surges

In modern times there have been some devastating storm surges in the area of ​​the North Sea coast. For example, two large storm surges in the 16th century, the so-called All Saints' Day floods in 1532 and 1570 , in which a total of more than 10,000 people lost their lives. More than 8,000 people were killed in the Burchardi flood in October 1634 and the island of Alt-Nordstrand was torn into several parts during the flood. The Christmas flood in 1717 killed around 11,500 people on the entire North Sea coast as a result of the floods, while the New Year flood from December 31, 1720 to January 1, 1721 broke the island of Helgoland in two.

Dike types

Depending on the width of the foreland and the slope of the outer slope , the dikes were reinforced differently. If the slope was 1: 3, the dyke was additionally reinforced with turf as a cover, whereas the dyke at the foot end was covered with straw.

In the event of a higher risk and need, the dyke body was additionally secured by wooden posts with adjacent planks. Furthermore, so-called "Bermedeiche", which had a slope of 1: 7, were covered with straw. In order to counteract strong waves, stone ceilings were partly laid, which, however, represented a high cost factor and was therefore implemented less often. More often it happened that created inner embankments had a slope of 1: 1 and these were insufficient with stronger currents.

Wooden groyne (breakwater) on the North Sea

Additional protective devices

Groynes are dams protruding from the beach into the sea. These can be oriented at right angles, upstream or downstream. This reduces the speed of the currents running parallel to the coastline. Among other things, this led to the erosion of the respective coastal sand being weakened and the accumulation of the sand in the floods being increased. Depending on the material used, they were given different names: wood (name: Höft), shrub and weak posts (stack) fascines with stone cover (Schlenge).

After Frederick the Great became Prince of East Frisia, he ordered that from now on, planks should be made of stone and no longer of wood for new buildings . The decision is based on the susceptibility and the associated maintenance costs of the old wooden planks.

Dike law

Due to the historical development of Germany and the associated self-administration of the individual landscapes, the dyke law has developed differently depending on the region. The overriding objective that the people living on the march had to contribute to the protection of the dike without being given specific guidelines was now considered to be generally applicable. For example in the East Frisian Land Law of 1515 or the Spadeland Law of 1557.

In the middle of the 16th century, the influence of the state and sovereign rulers on dike associations increased. In addition to their claim to the dike foreland, the sovereigns were interested in protecting and administering this land, which was expressed by influencing the dike administration. This was favored by grievances that prevailed within the dike cooperatives. The motives were the " paternal care, the desire for profit, the lack of grain, the longing for security and the urge to settle . "

The public-law structures of the dike associations, which were pronounced in the Middle Ages, led in the early modern period to the fact that the state sovereigns treated these associations like state institutions. Although they officially retained the rights as a separate body, they were subject to the supervisory and police powers of the authorities. As a result, they lost their independence during this phase. This process did not take place equally in all parts of the North Sea, but it affected most of the landscapes. Exceptions were still free areas of Germany, in which the different dike associations then merged or cooperated. When the great storm surges caused emergencies, it was the rulers of other areas who asked for support and help from the free associations.

The fact that the municipal corporations were able to manage themselves again was due to the Prussian Dyke Act of 1848. The democratic progress was continued or introduced with the dike and sluice regulation for East Friesland (DSOfO) of June 12, 1853 and the dyke regulation for the Duchy of Oldenburg (ODO) of June 8, 1855. They were laws that were discussed on a parliamentary basis. This new philosophy of state supervision and self-administration was justified. a. with the uprisings of the Revolution of 1848 , which, although it failed to achieve its primary goal, nevertheless encouraged people to have a say. The Bremen dyke regulation of July 29, 1743 is a counterexample , as " it prevented further organic development of the dyke conditions ".

Dike construction since the 20th century

At the beginning of the 20th century, the storm surges that occurred were less destructive for the coastal residents than in the previous centuries. This was mainly due to the significant improvements in the warning systems as well as the research facilities , which were able to make comprehensive forecasts through newly established facilities such as the wind jam and storm tide warning service. For example, changes in water level in the North Sea coastal areas were measured by numerous gauges. In addition, a new research center for island and coastal protection was founded in the mid-1930s, based on the island of Norderney.

New opportunities

Asphalted dike

When building the dykes, new possibilities also emerged, for example through the use of carts or field railways, which replaced manual labor and made projects that could not be implemented up until then possible. New materials also proved useful, such as asphalt and various types of stone that were made usable by large mixing plants. The paved dike foot protection, which was customary up to that point, could be made more stable with asphalt and protect the sward behind from the wave energy with a rough surface made of a combination of asphalt and stone. A subsequent rough strip formed the transition to the asphalt surface and for the first time consisted of further gravel and stone casting masses.

Drainage system

Not only did the construction of the dyke experience innovations in the course of the 20th century, but also the drainage of the inland areas behind the dyke could function larger and more efficiently. The existing sewers, which justified their necessity mainly in agriculture, were able to work independently of the tide by pumps and to compensate for large fluctuations. Especially due to the morphological change of the coastline, which increased significantly due to the coastal protection measures, but also due to less sensitive arable land, low tidal water levels were not uncommon. Additional flooding of the agricultural areas that occurred in the winter months justified the immense need for improvements in drainage performance.

Land reclamation

Land reclamation near Westerhever, Eiderstedt

Another aspect that pervades coastal protection from the beginning of the 20th century to the present day is land reclamation . From 1900, under Prussian administration, the Wadden Sea was silted up over a large area. Due to the accumulation of sediments, grasses could settle and over time the newly reclaimed soil could be made usable for agriculture. A result of the land reclamation are today's crags or polders . From the 1950s, the point of view of coastal protection came to the fore as the driving force behind land reclamation and, with it, the ecological aspects of siltation.

Severe storm surges in the 20th century

Netherlands 1953

Delta Works

A storm surge occurred in the Netherlands in February 1953 , which prompted people in Germany to think about the previous coastal protection. Because a 23-hour hurricane destroyed 500 km of dykes and dunes and killed 1835 people, tens of thousands lost their homes. It was only with luck that the dike on the Hollands IJssel would not have broken, otherwise the residential area would have been flooded by 1.5 million people. After the severe storm surge in the Netherlands, extensive changes were made in Holland, such as the construction of the Delta Works . This created better protection against further storm surges and new infrastructures.

In Germany, the Dutch disaster led to the previous coastal protection program being reconsidered and modified. For example, the “decisive storm surge water level” was adapted to the level from February 1953 and included in the model of the frequency method, which is common in Schleswig-Holstein. Frequency methods are to be defined as follows: The "decisive storm surge water level" may occur / be exceeded a maximum of once per centennium and consists of the sum of the pre-calculated spring tide high water and the highest recorded wind congestion.

Germany 1962

Hamburg storm surge 1962

Although the need for safer coastal protection was recognized, the storm surge in February 1962 created great dangers for people in all parts of the German North Sea coast. Although only a few kays were flooded, Hamburg in particular suffered severe damage. 315 people died there, a total of 340. This is due to the fact that the “decisive storm surge water levels” were not reached on the coast, but were exceeded significantly in the estuary of the Elbe. The securing of the dykes, which was ordered in 1955, was not yet completely finished and so 60 dykes broke in Hamburg alone. In addition, the dyke construction was inadequate, as the inner slope of the dyke was too steep and the wave heights were higher than forecast.

Germany 1976

This storm surge hit water levels that were previously higher than any recorded value (Elbmarschen: 38 centimeters higher than 1962). Nevertheless, the damage turned out to be minor, as the planned dike heights or redesigns were well advanced. The extent of the forces only became clear in areas that were not repaired.

Dikes or other protective functions

Eider Barrage

Storm surge barriers

The construction of storm surge barriers from the 1960s onwards made it possible to shorten the line of the dike considerably, so that further elevation and repair measures could be saved. One example is the Eidersperrwerk which was completed in 1973 and has brought some benefits: the saving of 62 km of dike length, protective leave the Eider from storm surges, shipping possible on the Eider and the receiving water for the large catchment area of the Eider compared to before improve.

Dyke construction

Sand has proven to be a useful material for the construction of dykes when used in connection with a washout. Because in sand dykes, a coat of clay is piled up, which works effectively against erosion. The top layer of the dykes is a dense sward, which primarily protects against washouts. If cement flooring is not available, concrete can also be used as a building material, for example in Hamburg-Neuenfelde .

Current situation on the North Sea coast and outlook

The west coast of Schleswig-Holstein , with its total size of 3400 km², a coastline of 533 km and a share of 364 km of land protection dikes, is the central issue with regard to coastal protection in the state. Nowadays one tries to bring the hazard potential of the North Sea and the different demands of society better in harmony with those of the natural environment. For this reason, there is a new orientation of the coastal protection, which in the past mainly focused on the maintenance of the dikes. The protection of the islands, Halligen and the Elbe estuary with their mud flats, tides and sediment transport represents an enormous organizational and financial expense (approx. 50–55 million euros annually) that the responsible authorities have to manage.

Hazard analyzes

Hazard analyzes calculate the potential for damage in the event of a flood and include a risk assessment. They mostly happen without considering the geologically and historically known landscape development. These calculations result in the highest damage potential, especially for urban settlement areas, marshland areas on the Elbe and the North Frisian Islands that are not bounded by central dikes (especially in relation to the densely populated Sylt).

Modern forms of coastal protection

Tetrapods

Tetrapods as coastal protection (Hörnum / Sylt)

Tetrapods act to secure solid structures, as they are positioned in front of the foot of the building and protect against erosion there. They consist of a ball from which 4 truncated cones emerge. Tetrapods are used, for example, at the southern end of the island of Sylt , where they take on the function of breakwaters and reduce the energy of the waves that hit them.

Due to their high weight, the tetrapods tended to sink into the sandy soil in the past. To counteract this process, a sand bed is first prepared, which is then covered with geotextiles. Since the costs for a new production and for the transport of the tetrapods are over 1000 € each, it is cheaper to dig up sunken tetrapods and erect them at a new location. But not only sunken tetrapods pose a problem - the goal of reducing sand erosion often cannot be achieved either. The tetrapods on Hörnumer Strand were washed away and there was increased sand erosion at the southern end of the structure. Tetrapods currently only protect the beach section in front of Hörnum, the rest of Hörnum Odde is exposed to the tides. This is mainly due to its status as a nature reserve . Nonetheless, local residents sometimes criticize the lack of coastal protection measures.

Sand washes

Sand flushing off Sylt

Sand was first carried out on the island of Sylt in 1972. Since 1984 there has been regular sand flushing along the entire west coast of Sylt, so that around 48 million cubic meters of sand had been washed up by 2016. The sand is removed from an area around eight kilometers off the coast with a flushing ship. The excavator sucks a sand-water mixture from a depth of 15 to 30 meters to the surface, where the water drains off. The sand remains in the hold of the ship. The ship then moves up to about 1.2 kilometers from the coast and picks up the floating end of the flushing line. The sand is pumped through this line to the beach and distributed there with bulldozers. These measures made it possible to restore the beach on Sylt's west coast. In addition, fore dunes can be built, which prevent the retreat of dunes, the demolition of cliffs and the destruction of coastal protection measures.

But sand flushes are also criticized because they are very costly. Sand washings on the island of Sylt cost a total of around 9.3 million euros in 2017. If the sea level continues to rise, the amount of sand to be washed up will also increase accordingly. For this reason, costs can be expected to continue to rise in the future. By removing and washing up the sand, this form of coastal protection also interferes with the natural dynamics of ecosystems.

outlook

The rise in sea levels associated with climate change will also have an impact on the German North Sea coast. A rise in the North Sea of ​​around 50 centimeters is assumed for the next 100 years. So that people can live near the North Sea in the long term, new coastal protection measures must be tested.

Climate dike

In Schleswig-Holstein there are already the first climatic dikes in Büsum and Nordstrand, and another is to be built in Dagebüll. Climate dykes differ from conventional dykes in that they take future developments into account and allow for further sea level rise. The existing dike, which will be reinforced and raised somewhat, serves as the starting point. In addition, it is flatter than before on the side facing the sea, so that the swell can run out flat on the outer slope of the dike. Furthermore, the crown of the existing dike will be widened from two and a half to about five meters. This will benefit future generations, who can strengthen and raise the dike even further without the dike foot having to be widened. In this way, the dike can be adapted to a sea level rise of one to one and a half meters. Climate dikes are considered the future of dyke construction in Schleswig-Holstein, so that all future dike reinforcements should be based on the principle of the climate dike.

But this coastal protection measure is also cost-intensive. The construction of the climate dike in Nordstrand alone cost 32 million euros. In addition, stones could endanger the stability of the dike. The stones can loosen at high tide, so that the water would remove even more soil from the holes. For this reason, special machines in Nordstrand had to remove the stones from the top layer of the dike to a depth of around 30 centimeters.

literature

• Johann Kramer: No dike. No country. No life. History of coastal protection on the North Sea. Rautenberg, Leer 1989, ISBN 3-7921-0414-8 .
• Johann Kramer, Hans Rohde: Historical coastal protection. Dyke construction, island protection and inland drainage on the North and Baltic Seas. Stuttgart 1992, ISBN 3-87919-163-8 .
• Hansjörg Küster: History of the landscape in Central Europe. From the ice age to the present. CH Beck, Munich 1999, ISBN 3-406-45357-0 .
• Rolf Meurer: Hydraulic engineering and water management in Germany. Past and present . Vieweg + Teubner, Wiesbaden 2000, ISBN 3-322-80214-0 .

Individual evidence

1. ↑ Sabine Mertsch: Risk management as a concept for risk minimization using the example of the coastal areas of Schleswig-Holstein at risk of flooding . Bonn 2004, p. 16.
2. ^ Rolf Meurer: Hydraulic engineering and water management in Germany. Past and present . Vieweg + Teubner Verlag, Wiesbaden 2000, ISBN 978-3-322-80214-9 , p. 16 .
3. ^ ^{A b c} Rolf Meurer: Hydraulic engineering and water management in Germany. Past and present . Vieweg + Teubner Verlag, Wiesbaden 2000, ISBN 978-3-322-80214-9 , p. 17 .
4. ↑ Herre Halbertsma: Terpen tusschen Vlie en Eems . JB Wolters, Groningen 1963.
5. ↑ Georg Kossack, Karl-Ernst Behre, Peter Schmidt: Archaeological and scientific research on rural and early urban settlements in the German coastal area from the 5th century BC. Chr. To the 11th century AD. Chr . Ed .: Acta Humaniora. tape 1 . Weinheim 1984.
6. ↑ ^{a b c d e f g} Johann Kramer: No dike, no land, no life. History of coastal protection on the North Sea . G. Rautenberg, Leer 1989, ISBN 3-7921-0414-8 ( worldcat.org [accessed January 4, 2018]).
7. ↑ Hansjörg Küster: History of the landscape in Central Europe. From the ice age to the present . CH Beck, Munich 1999, ISBN 3-406-45357-0 , p. 222.
8. ↑ Hansjörg Küster: History of the landscape in Central Europe. From the ice age to the present . CH Beck, Munich 1999, ISBN 3-406-45357-0 , p. 224.
9. ↑ ^{a b} Sabine Mertsch: Risk management as a concept for risk minimization using the example of the coastal areas of Schleswig-Holstein at risk of flooding . Bonn 2004, p. 22.
10. ↑ Andreas Busch: An old land surface and traces of culture in the Nordstrander Watt . In: The coast . tape 8 , 1960 ( handle.net [accessed January 4, 2018]).
11. ↑ Daan P. Hallewas: Medieval sea dikes in the Dutch coastal area . tape 15 . ROB, Hildesheim 1984.
12. ^ Karl Lüders, G. Luck: Small coastal dictionary . Hildesheim 1976.
13. ↑ T. Huitema: Dijken langs Zee, Rivieren en Kanalen- Kaden on polder, Droogmakerijen Enz . In: Kosmos . NV Uitgevers-Maatschippij Kosmos, Amsterdam-Antwerp 1947.
14. ↑ Albert Bantelmann: The agricultural development in the North Frisian coastal area, a functional chronicle through five millennia . In: The coast . No. 14 . Board of Trustees for Research in Coastal Engineering (KFKI), Hamburg 1966.
15. ^ Karl-Ernst Behre: Landscape history of Northern Germany. Environment and settlement from the Stone Age to the present . Wachholtz, Neumünster 2008, ISBN 978-3-529-02499-3 .
16. ^ ^{A b} Karl-Ernst Behre: Landscape history of Northern Germany. Environment and settlement from the Stone Age to the present. Wachholtz Verlag, Neumünster., ISBN 978-3-529-02499-3 , pp. 92 .
17. ↑ NDR: How Dithmarsch farmers defeated the king. Retrieved January 22, 2018 . 
18. ^ Peter Henning Feindt: Environmental and technology conflicts . 1st edition. VS Verlag für Sozialwiss, Wiesbaden 2010, ISBN 978-3-531-17497-6 , p. 299 .
19. ↑ ^{a b c} Dirk Meier: The North Sea Coast. Story of a landscape . Boyens, Heide 2006, ISBN 3-8042-1182-8 , p. 108.
20. ↑ ^{a b} Dirk Meier: The North Sea Coast. Story of a landscape . Boyens, Heide 2006, ISBN 3-8042-1182-8 , p. 109.
21. ↑ ^{a b c} Trilateral considerations on coastal protection in the Wadden Sea taking into account the planned EU flood protection directive .: Trilateral considerations on coastal protection in the Wadden Sea taking into account the planned EU flood protection directive. (PDF) Retrieved January 28, 2018 . 
22. ^ ^{A b c d} Rolf Meurer: Hydraulic engineering and water management in Germany. Past and present . Vieweg + Teubner Verlag, Wiesbaden 2000, ISBN 978-3-322-80213-2 , p. 39 .
23. ^ ^{A b} Hansjörg Küster: North Sea: History of a landscape . Wachholtz, Kiel 2015, ISBN 978-3-529-07604-6 , pp. 72 .
24. ^ Michael hut: Ecology and hydraulic engineering. Ecological principles of water management and the use of hydropower . 1st edition. Vieweg + Teubner Verlag, Berlin 2000, ISBN 978-3-528-02583-0 , p. 133 .
25. ↑ ^{a b} Rolf Meurer: Hydraulic engineering and water management in Germany: past and present . Vieweg + Teubner Verlag, Wiesbaden 2000, ISBN 978-3-322-80214-9 , p. 40 .
26. ^ Johann Kramer, Hans Rohde, German Association for Water Management and Cultural Building: Historical Coastal Protection. Dyke construction, island protection and inland drainage on the North and Baltic Seas . K. Wittwer, Stuttgart 1992, ISBN 3-87919-163-8 , pp. 189 .
27. ^ Johann Kramer, Hans Rohde, German Association for Water Management and Cultural Building: Historical Coastal Protection. Dyke construction, island protection and inland drainage on the North and Baltic Seas . K. Wittwer, Stuttgart 1992, ISBN 3-87919-163-8 , pp. 191 .
28. ^ Johann Kramer, Hans Rohde, German Association for Water Management and Cultural Building: Historical Coastal Protection. Dyke construction, island protection and inland drainage on the North and Baltic Seas . K. Wittwer, Stuttgart 1992, ISBN 3-87919-163-8 , pp. 190-191 .
29. ^ Johann Kramer, Hans Rohde, German Association for Water Management and Cultural Building: Historical Coastal Protection. Dyke construction, island protection and inland drainage on the North and Baltic Seas . K. Wittwer, Stuttgart 1992, ISBN 3-87919-163-8 , pp. 192 .
30. ^ Warnke, Ingo: Paths to cultural language. The polyfunctionalization of German in legal discourse (1200-1800) . De Gruyter, Berlin 1999, ISBN 3-11-016429-9 , pp. 403 .
31. ^ Johann Kramer, Hans Rohde, German Association for Water Management and Cultural Building: Historical Coastal Protection. Dyke construction, island protection and inland drainage on the North and Baltic Seas . K. Wittwer, Stuttgart 1992, ISBN 3-87919-163-8 , pp. 193 .
32. ^ Johann Kramer, Hans Rohde, German Association for Water Management and Cultural Building: Historical Coastal Protection. Dyke construction, island protection and inland drainage on the North and Baltic Seas . K. Wittwer, Stuttgart 1992, ISBN 3-87919-163-8 , pp. 194 .
33. ↑ ^{a b c d e f g h i j} Rolf Meurer: Hydraulic engineering and water management in Germany. Past and present . Vieweg + Teubner Verlag, Wiesbaden 2000, ISBN 3-322-80214-0 .
34. ^ ^{A b} Dietmar Wienholdt: Planning and measures of the state Schleswig-Holstein for coastal protection. Coastal protection today and tomorrow. Lecture event on November 3rd, 2008 in Niebüll . In: Hans Otto Meier (Ed.): Nordfriesland in conversation . No. 6 , 2008.
35. ↑ ^{a b} Dirk Meier: Schleswig-Holstein's coasts in transition. From the ice age to global warming . Heath 2007.
36. ^ Rolf Meurer: Hydraulic engineering and water management in Germany. Past and present . Vieweg + Teubner Verlag, Wiesbaden 2000, ISBN 3-322-80214-0 .
37. ↑ ^{a b} Technical plan for coastal protection Sylt. (PDF) 2015, accessed on January 17, 2018 . 
38. ↑ ^{a b} Melanie Steur-Fiener: Tetrapods on Sylt: The four-armed colossi are moving. Retrieved January 17, 2018 . 
39. ^ Kieler Nachrichten, Kiel, Schleswig-Holstein, Germany: How Sylt fights for its coast. Retrieved January 17, 2018 . 
40. ↑ ^{a b c d} Coastal protection on Sylt. Sand flushing 2017. (PDF) State Office for Coastal Protection, National Park and Marine Protection Schleswig-Holstein (LKN.SH), accessed on January 17, 2018 . 
41. ↑ ^{a b c d e} n-tv news television: Germany has the first climate dike . In: n-tv.de . ( n-tv.de [accessed on January 28, 2018]).
42. ↑ ^{a b} NDR: New super dyke is not so great. Retrieved January 28, 2018 .