Workshop: Dike Building, Storm Surges and Land Losses at the North-Sea coast of Schleswig-Holstein, Germany

Workshop: Dike Building, Storm Surges and Land Losses at the North-Sea coast of Schleswig-Holstein, Germany

The paper gives a short overview about the landscape development and settlement history along the North-Sea coast of Schleswig-Holstein, Germany. Geoarchaeological investigations have been undertaken by the Coastal Archaeology by the Research- and Technology Centre of the University of Kiel under the project management by the referent in Dithmarschen and Eiderstedt and in North-Frisia by the University of Kiel as well as the State Archaeological Service (Archäologisches Landesamt).

The landscape development of the coastal landscape of the North-Sea coast of Schleswig-Holstein was formed by the increase of the Geomorphology, the raise of the sea level as well as dike building and drainage by the humans. The salt marshes of Dithmarschen between the estuaries of the Elbe and the Eider were first inhabited since the birth of Christ during a period of a lower sea level. Most of these settlements were founded on high silted up banks. The inhabitants of these settlements protected themselves by the constructing their houses on artificial mounds, called Wurten. The salt marshes of Dithmarschen, which extended westward the old moraines and beach ridges were settled during the 1st century AD. Here, the earliest settlement in the salt marshes are located in long-south orientated lines. Larger excavations between 1998 and 2002 in Süderbusenwurth have pointed out the existence of Wurten with stable houses on a higher tidal channel bank around 50 AD which were raised further on since 150 AD. At the end of the 3rd century AD the Wurt settlement was abandoned. In the northern salt marshes of Dithmarschen small settlements are arranged two lines to the west of the Pleistocene hinterland. Larger Wurten existed along the estuary of the river Eider. The best known example is Tofting near Tönning, which was founded in the 1st century AD and abandoned during the 6th century AD. Northward of Eiderstedt the today North-Frisian Wadden-Sea formed a peat landscape eastward a barrier coast of beach ridges and old morains. Therefore settlements of Roman period are only known from the morains isles.
                      The economy of these Wurt-settlements based on husbandry, esp. on cattle grazing in the salt marshes which formed the environment of the settlements. Small-scale arable farming of plants like horse bean (Vicia faba), barley (Hordeum vulgare), oats (Avena sativa), Emmer (Triticum dicoccon) and flax (Linum usitatissimum) were only possible on higher banks during the summer months. The end of the first phase of the habitation of the clay district ended in the most areas lately in the 5/6th century AD. This might be not the result of more storm surges but also the consequence of the Migration period. There is no doubt that groups of Angles and Saxons migrated to England, but the question is how large these groups were. Too little is known about the settlement pattern between the time of 400–600 AD in North-West Germany, in other clay districts, like in Westergo in Frisia, the habitation still going on during the Migration period.
Favourable natural conditions and a low sea level permitted the renewed colonization of the salt marshes in the North-West German clay district starting in the 6/7th century AD. During this time, new salt marshes had developed. The resettlement of the old salt marshes of Dithmarschen between the Elbe and the Eider by rural farmers started at the end of the 7th century AD. At this time, this area belonged to three North Elbian Saxonian tribes, which are described by Adam von Bremen in the history of the church of Hamburg (II, 17) with the words: Transalbianorum Saxonum populi sunt tres. Primi ad occenaneum sunt Tedmarsgoi, et eorum ecclesia mater in Melindorp [Meldorf]. Charlemagne conquered these Saxonian tribes in AD 798. During this time the salt marshes of Dithmarschen are one of the regions with the heighest population of clay districts in Schleswig-Holstein. In southern Dithmarschen the settlements of this period occur in the same area as the settlements of Roman times. In the northern part the early Medieval Wurten were established west of the region of the old Roman settlements, because bogs had spread over the inner part of the salt marshes after AD 400. The best example of a Wurt of the early Medieval time with many habitation layers is Wellinghusen near Wöhrden. Here, a ground settlement was established at the end of the 7th century AD. Since the beginning of the 9th century the new stable houses were erected on single Wurten. Later on a large village mound developed and was raised several times until the 14th century AD. The 10th century saw the beginning of an increase in colonization and resulted in the establishment of new Wurten.
The colonization of the salt marshes north of the river Eider, which occurred during the 8th century AD, is connected with a Frisian immigration. On the higher river banks large mounds were built in Elisenhof near Tönning and Welt. Botanical investigations show that extremely halophytic conditions existed around these settlements. In Elisenhof a group of stable houses, surrounded by fences, were built as ground level settlements and later on raised with dung and clay. As during the Roman period, livestock was the economic basis of these settlements. The beach ridges of Eiderstedt were populated at that time, too.
Unfavourable environmental conditions due to the extensive peat bogs and swampy areas along the many parts of the North-Frisian coast prevented colonization before AD 1000. Only the Pleistocene areas and flooded salt marshes in the western part of the tidal flats around the present island of Pellworm and Hallig Hooge were inhabited. These findings indicate that in early Medieval times salt marshes, located inland of the sand ridges, existed in the western part of the present North-Frisian Tidal flats. Excavations during the “Norderhever-Project” have discovered a ground level settlement of the 9/10th century AD, which was flooded in the late Middle Ages. By then, the sea level had risen so much that people could no longer live in houses built on top of the marsh land in North-Frisia. Beach ridges in the West had been eroded and destroyed by waves and currents and, consequently, salt marshes were flooded too often during storm surges. Thus, mounds (Wurten) had to be built to protect against the rising waters. A number of settlements and burial mounds are also recorded on the Pleistocene deposits of the islands of Amrum,
Föhr and Sylt.
Since the high Medieval Age, the entire area of the sea and river marshes were intensively cultivated and more densely populated than ever before. In the 11th and 12th century the building of dikes and drainage of land began. Initially, the dikes were not high enough to protect low-lying land against higher storm surges. More salt marshes – such as those in the northern part of Eiderstedt in Schleswig-Holstein – were colonized, and the landward swampy areas were drained. The local people generally took the initiative for the construction of dikes. The wealth of the leading families was based on the systematic drainage and colonization of the inland marshes and bogs. This started the transition from a natural landscape to the present cultivated landscape.
The earliest dikes were built around the arable fields and meadows to keep out the occasional spring and summer floods. In the 13th century, these ring dikes were connected and raised. The sea dikes along the Dithmarschen between the Elbe and the Eider were built by cooperatives which had been organised in parishes. These cooperatives – in Dithmarschen called Geschlechter – decided about the location, design, construction and maintenance of dikes, drainage systems and sluices. In the newly drained areas the farms of the cooperative settlements, built on little single Wurten to protect against flooding form inland waters, were arranged in the landscape like beads on a string. Their narrow strips of fields penetrated farther and farther into the peat marsh. Moreover, in the salt marshes of Dithmarschen new village Wurten were established and mounds mostly constructed with clay.                                                                      On the low marshes of northern Eiderstedt numerous tidal channels separated island-like patches with mounds of clay. Even today these mounds still determine the appearance of the landscape in Westerhever, and around Osterhever and Poppenbüll. Because salt water often inundated the low marshes, many of the mounds were suddenly raised in one construction effort. The cooperatives, which settled on these Warften also built dikes around their cultivated land and within single house Warften were constructed.
A consequence of diking was the water level increase during storm surges due to the reduction of the flood plains. Especially storms from the North-West forced water into the German Bight and the estuaries, and breaches of the dikes were common. Therefore, the dikes were built higher after the 13/14th century. Since the late Medieval time, heavy storm surges eroded and destroyed the higher banks near the coast. Salt water penetrated the low lying swampy areas and covered the peat with sediments. Due to extensive draining and subsequent compaction of the soil the surface had sunk. Several catastrophic storm floods eroded vast areas and created new large bays.
According to numerous archaeological investigations, the outer salt marsh of North- Frisia were not colonized until the early Middle Ages. Several archaeological sites around Hallig Hooge, as well as the island of Pellworm delimit an area of earliest Frisian habitation in the 8th and 9th century. As well as in the north-part of Eiderstedt the oldest `Warft´en traced back until the 12th century. After building of dikes also the low-lying marshes were colonized between the 12th and 14th century.
Since the late Middle Ages North-Frisia (Uthlande) suffered great losses of land. During the catastrophic storm surges of 1362 and 1634, a large part of the Uthlande between Eiderstedt in the South and the island of Sylt in the North was completely lost. The so-called Edomsharde with the famous port of Rungholt was totally destroyed. The salt marsh areas below Mean High Water (MHW), which had been occupied and cultivated by man since the 9th and 12th century, became a permanent part of the tidal flats. Cultural remains of the 12th until the 14th century AD had been unearthed around the younger Hallig Südfall. The reasons for these catastrophes are due to the geological development as well as to the activity of the people by water drainage and salt cutting. In particular, the exploitation of the coastal area by its inhabitants has to be blamed for the disaster.
However, the coastal population could not know that the geological subsidence of the land, which depended on the relief of the glacial surface and the type and thickness of the overlying marine deposits, had not yet come to an end. Large tidal channels and gullies such as the Norderhever cut into the salt marsh area. These tidal creeks followed old glacial smelt water valleys of the pre-Holocene landscape.
But also the settlers themselves contributed to the subsidence of the coastal marshland by the construction of dikes, systematic drainage of the area and, in particular, by peat cutting for the production of salt. Remnants of peat cutting activities can be observed in the vicinity of the Hallig Langeness and at other locations of the inner part of the North-Frisian tidal flats. In Medieval times the settlers in this area sustained themselves on the basis of agriculture and salt production. The raw material for salt production was the peat of the upper organic deposits. It was cut systematically over large areas. The earliest report of salt production is from SAXO GRAMMATICUS (1180). Around the time of AD 1230, taxes had to be paid for salt production.
The second disastrous storm surge of 1634 also turned extended areas of coastal marshland into tidal flats. The large island of Strand was divided into the islands of Pellworm and Nordstrand as well as a group of smaller islands (Halligen). Subsequent attempts of reclamation of these areas were unsuccessful. They are still part of the cultural heritage and signs of the changing geography, landscape and settlement history.

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