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Coastal development, sea-level change and settlement history during the later Holocene in the Clay District of Lower Saxony (Niedersachsen), northern Germany
Abstract
This paper focuses on the last 4000 years of coastal evolution and settlement in Niedersachsen (Lower Saxony). Due to a decrease in the rate of sea-level rise during the later Holocene, regressions took place, which included calmer phases, during which intercalated peat developed. The first marked regression started at ca. 1500 BC (calibr.). As a result, peats formed which can be traced into the tidal flats far beyond the present coastline. During the following Dunkirk I transgression period, several bays were created and the coast took on its present-day outline. Shortly before the Birth of Christ, a second pronounced regression occurred, which resulted in soil formation and led to a far-reaching human occupation in the Clay District, i.e. the so-called Marsch. For this time, and also for the period around AD 800 as well as for around AD 1500, the entire coastlines have been reconstructed. Increase in storm-flood level from the 1st century AD onwards was responded to by the local population by the construction of dwelling mounds, i.e. Wurten. Diking started in the 11th century and by the 13th century a continuous system of winter dikes had been created. The cutting-off of the hinterland by diking resulted in higher storm-flood levels. Severe breaches of the Medieval dikes led to the formation of large bays such as the Dollart, Ley Bay, and Jade Bay as a result of higher storm-flood levels which, in turn, were caused by diking. The formation of these new bays resulted in large-scale changes in hydrographic conditions in the hinterland and, as a consequence, existing bays sometimes silted up. The consequences of short-term storm flood events are compared with the long-term effects of the changing drainage system.
... If these are succeeded by very violent tempests blowing from the N. W., the effect is, to propel the sea with great violence southward through the British Channel: but the straits of Dover are too narrow to admit the augmented body of water readily to pass, and in consequence it falls back upon the coast of Holland (Murray, 1838). If the storms of the North Sea made Belgium, Holland and Germany subject to marine ingressions and fluvial floods capable of wiping out vast areas and settlements -but in the examples of the Dolard/Dollart or Jade Bay shaped in the last centuries of the Middle Ages (Behre, 2004 and Figure 24) it is Knottnerus (2004b) who reminds us of the certain responsibility of human activities -in the same centuries in the Mediterranean one could look without excessive apprehension at the less devastating erosive phenomena, also because between the 16th and 18th centuries vast coastal areas distinguished by low sandy shores were advancing and totally depopulated. Tidal oscillations, enhanced by Scirocco winds, have more relevant measures in the upper Adriatic Sea. ...
... We know that the Gulf of Dollart is the result of a marine ingression that began in the last decades of the 13 th century capable of wiping out dozens of villages and causing tens of thousands of deaths, and that during the flood of Cosmas and Damian in 1509 reached its maximum extension, i.e. ca. six times its modern size (Behre, 2004). Large areas of Friesland were invaded by the Ocean in the 533, 792, 806, 839, 1164, 1170, 1210, 122I, 1230, 1237[…] 1248, 1249, 1250. ...
People living along the coast have always had to deal with the protection from sea. In this multi-millennial history, hard or rigid engineering (meaning constructions made of stone and rocks, pozzolan and hydraulic cements) have alternated or integrated with naturalistic ones. Such alternation, at least until the diffusion of chemical hydraulic cements and Portland, has not been synchronic in the coastal areas of the Mediterranean and North Sea. Still today, independently from the widespread revival of naturalistic (or ecological) engineering and from the debate on the results of hard and soft engineering, vast sectors of the planet are protected by natural dunes, earthen and beaten sand dikes or by wooden works and fascinage.
The evolution of seaworks is a long-lasting process, not linear at all, where hydraulic science, beyond the specific weather and sea conditions, had to reckon with the investment of ruling classes, societies, and states.
Design, techniques, and materials used, highlight the continuity with the history of river nanagement but also with the equally millenary experiences gained in salt marshes, fish farms, in the construction of ports, in the defense from hostile or rival groups and societies and in the fortification of coastal cities that, well before the littorals, have attracted studies and projects.
This legacy will be discussed in chapter 1 mainly with European examples. The following chapters, dedicated to the centuries that run from 14th to 19th, focus on the scientific literature, on models and techniques implemented on two seas: the Northern Adriatic Sea with the lagoon of Venice (in the modern period the only Italian area to be seriously threatened by the sea) and the North Sea with France, Belgium, Holland and Germany. Two areas distinguished by morphology and meteo-climatological phenomena that have produced a literature not always in agreement in identifying the causes of erosion or marine ingressions and in interpreting the circumstances that have determined the local evolution of the seaworks.
Complicating our reconstruction are the political and military events of Belgium, Holland and Northern Germany from the Middle Ages to the modern age They are reflected in a definition of geographical areas that is not always clear and consistent. In many 17th and 18th century Italian documents, the term United Provinces (the Republic of the Seven United Netherlands existed from 1588 until 1795) was used to refer to political entities whose territory included portions of Belgium, Holland and Luxembourg. Sometimes “Holland” could include areas of Belgium, otherwise referred to as Flanders… but Flanders extended from Calais (France) to all Belgium up to and including the Scheldt delta. Add to this that from 2018-2019 the Dutch government has decided to stop describing itself as Holland to use the Netherlands as the official name of this country. In the following lines we will follow those Dutch authors (including those who wrote in times very close to us) who use “Holland” to identify their homeland.
Chapter 5 focuses on groynes. Our lines (embarrassed by the linguistic evolution of the different areas and sacrificed by our polyglot limits) will inevitably look at only a part of that endless panorama of descriptive sources which have developed since the 16th century and at an equally large historical cartographic horizon which, together with the illustrations accompanying historical manuals and documents, is essential for a better understanding of the following pages. For the Middle Ages, Venice left the most extensive documentary and bibliographic heritage. In the lagoon context, the groynes, for centuries, have played a fundamental role in an integrated system whose reconstruction, here as in the North Sea, cannot disregard the analysis of dikes.
... Other extremely deadly storm surges happened in the 14th and 17th centuries. Dramatic changes to the coastal environment are not only proven by historical sources [72], but also by environmental and sedimentological data [73,74]. Rivers are the second-largest source of flooding hazards in Germany. ...
This paper demonstrates how historical research is a valuable tool for identifying past geological, geomorphological and climatic hazards and therefore critical for mitigating and reducing future risk. The authors describe the potential of a scientific field that straddles that of the geologist, geographer, historian and archivist. Historical records include a range of materials and sources of information, which can be very diverse; from written documents to cartographies, and from drawings to marble tombstones. They are all useful and convey important data, on the date of the event, the size of the phenomena, sometimes on ground effects, damage or magnitude. The authors discuss how to conduct historical research by providing a list of locations and how important historical documents can be found. Works that mention geological phenomena are listed, starting with the first occasional descriptions by individuals in letters, up to very specific publications in individual fields of interest. With this introduction, the editors of the Special Issue wish to draw attention to the importance of historical documentation, which is too often ignored or considered of low priority by the scientific community, but can contain key information on events, their impacts and social and cultural adaptations.
... This warm period was followed by a colder, more humid period, correlated with shifts in mean high-water levels and 14 C -dated archaeological findings from around 700 BC [48,49]]. This shift has been linked to changes in settlement patterns in the Wadden Sea area, leading to an expansion of salt marsh settlements during the following centuries [50,51]. The subsequent temperature drop is purported to have resulted in increased storm surges. ...
This study examines the occurrence of glendonite along coastlines since 1825, which have been previously referred to under different names such as Pseudogaylussite, Fundylite, and Kool Hoot across eleven sites. By utilising element ratios and 14C radiometric dating techniques, we establish a more accurate chronology for these varied sites ranging from 10 to 1 thousand years before the present (Ky BP). Sites include tidal flats, coastal barrier islands, and Wadden Sea environments. While some sites still exist, others are only known through publications and museum collections. Our research expands upon previous findings by presenting petrographic evidence that correlates with glendonite formation. Through the examination of the Olenitsa site on the Kola Peninsula, we demonstrate that marine bioclasts enclosed within concretions surrounding glendonites provide temporal context, suggesting that these outcrops were formed during a single event under changing conditions. Notably, certain sediment structures at selected sites indicate the occurrence of cold-water ice-raft storm events and the presence of drop stones. Furthermore, our paper explores the association of historic coastal sites with the formation of ikaite, highlighting the limitations of relying solely on geochemistry and isotopic analysis for interpretation. Intriguingly, we observe that pseudomorphs are abundant in specific areas but absent in adjacent regions with similar environmental, physical, and chemical conditions. No apparent connection is found between volcanic dust cloud-induced cold spells and glendonite. The distribution of coastal glendonites is more likely related to periods of climatic cooling through other means. We show that radiometric dating with 14C provides an indication of age, but the results can be erroneous due to the inclusion of older carbon sources in the analysis. The oldest locations discussed in this study are Kool Hoot (Alaska) and the river Clyde (Scotland), and the youngest glendonites discussed are from the Bay of Fundy in Canada. Occurrences from the Wadden Sea are intermediate in age and sit between the other two groups. The age of the Olenitsa site on the Russian Kola Peninsula is uncertain and still debated. We show that measuring the ratio of Mg/Ca can indicate how much the recrystallised ikaite preserved as calcite is influenced by diagenetic pore waters.
... Initially, only cultivated land was protected from storm surges by low ring dikes. But since the fourteenth century, a largely continuous coast-parallel dike line was established in order to protect the hinterland even against winter storm surges (Behre 1993(Behre , 2004Meier 1994). Nevertheless, devastating storm surges repeatedly pulled out large areas from the hinterland (for an overview, see Streif 1990;Higelke 1998). ...
Coastal zones at the German North Sea and the Baltic Sea were essentially caused by climate changes in the past. Humans have affected the dynamics of these systems by coastal protection and land reclamation. The salt marshes are regarded as one of the most natural ecosystems in Central Europe. At the same time, their function for coastal protection is in danger. As well as dunes, they are characterised by extreme abiotic conditions for plants and animals. Changes of abiotic conditions induced by climate change will affect the function and ecosystem services of coastal ecosystems, i.e. primary production, mineralisation, and soil development. These functions will especially affect the social subsystem, since the usability of the ecosystems for agriculture, coastal protection, water extraction, and tourism is directly concerned.
... The crevasses along the Old Rhine are all relatively elongated compared to reference cases that show much wider and shorter splays [for example, Columbia and Saskatchewan River, Canada -Smith et al. 2017), or semi-arid (sandy) environments -Sandover River Australia; Tooth (1999Tooth ( , 2005, Millard et al. (2017)]. Comparable elongated crevasses are typically observed in peatlands as avulsion belt crevasses in the Rhine-Meuse delta (Makaske et al., 2007;Pierik et al., 2018); but also in tidal swamp landscapes, elongated creeks have been found connecting former channels and former peat domes, for example in the South-western Netherlands (Schouwen Duiveland; Kuipers, 1960;Pons, 1992); around the Oer-IJ (Pons, 1992;Vos et al., 2015), and Ems estuary on the Dutch-German border (Behre, 2004). These crevasses reflect complex hydrological and nutrient regimes in often river-fed coastal swamps. ...
In the transformation from tidal systems to freshwater coastal landscapes, plants act as eco‐engineering species that reduce hydrodynamics and trap sediment, but nature and timing of the mechanisms of land creation along estuaries remains unclear. This article focuses on the Old Rhine estuary (The Netherlands) to show the importance of vegetation in coastal landscape evolution, predominantly regarding tidal basin filling and overbank morphology. This estuary hosted the main outflow channel of the river Rhine between ca 6500 to 2000 cal BP, and was constrained by peat during most of its existence. This study reconstructs its geological evolution, by correlating newly integrated geological data and new field records to varying conditions. Numerical modelling was performed to test the inferred mechanisms. It was found that floodbasin vegetation and resulting organic accumulation strongly accelerated back‐barrier infill, by minimizing tidal influence. After tidal and wave transport had already sufficiently filled the back‐barrier basin, reed rapidly expanded from its edges under brackish conditions, as shown by diatom analysis and datings. Reed growth provided a positive infilling feedback by reducing tidal flow and tidal prism, accelerating basin infilling. New radiocarbon dates show that large‐scale crevassing along the Old Rhine river – driven by tidal backwater effect – only started as nutrient‐rich river water transformed the floodbasin into an Alder carr in a next phase of estuary evolution. Such less dense vegetation promotes crevassing as sediments are more easily transported into the floodbasin. As river discharge increased and estuary mouth infilling progressed, crevasse activity diminished around 3800 to 3000 cal BP, likely due to a reduced tidal backwater effect. The insights from this data‐rich Holocene study showcase the dominant role that vegetation may have in the long‐term evolution of coastal wetlands. It provides clues for effective use of vegetation in vulnerable wetland landscapes to steer sedimentation patterns to strategically adapt to rising water levels.
... They formed before 4000 yr BP and are positioned below −5 m Mean Sea Level (MSL) (Hijma, 2016). In the second half of the Holocene, the Ems was a river with modest tidal influence, positioned in a coastal peatland environment, debouching into the Wadden Sea (Behre, 1999(Behre, , 2004Vos & Knol, 2015). These peatlands were reclaimed from the Middle Ages onwards, the Ems was embanked from around the year AD 1000 to the 13th century (Ey, 2010;Oost, 1995;Vos & Knol, 2015). ...
Estuaries comprise channels vital for economic activity and bars as valuable habitats. They are increasingly under human‐induced pressures (e.g., sea‐level rise and dredging), resulting in morphological changes that affect navigability, flood safety and ecology. Antecedent geology may strongly steer how estuary channels will adapt to these pressures, but is surprisingly absent in most models. Here geological data and a unique bathymetry dataset covering 200 years from the Ems‐Dollard estuary (Netherlands/Germany) were used to demonstrate how local resistant layers force the position and dimensions of confluences and bars on the scale of an entire estuary. These layers limit channel depth and consequently cause widening, resulting in mid‐channel bar formation and increased channel curvature. This could lead to unexpected estuary widening and may cause land loss in densely populated areas. With increasing channel volume (as may happen again under future sea‐level rise), resistant layers in the estuary’s substrate become more exposed, which enhances their effects. Many systems around the world contain shallow resistant layers that potentially constrain estuary channel dimensions and steer bank erosion. This highlights that resistant layer effects are important to consider as part of mixed depositional processes in coastal environments. It is therefore necessary to globally account for the effects of inherited resistant layers in the likely response of estuaries to sea‐level rise and increased tidal penetration.
The post-Pleistocene history of the German coasts is generally characterised by sea level rising, which was fast in the beginning and slower later. It was caused by the melting ice and a change of transgressions and regressions. Ca. 6000 years BP, human settlements at the coast began. Diking at the North Sea started in the eleventh century to protect the hinterland even against winter storm surges. Of the different ecosystems, salt marshes and sand dunes are widespread on both coasts. At the North Sea coast, salt marshes developed at the Wadden seaside of barrier islands and in front of sea dikes of the mainland. At the Baltic Sea coast salt meadows have developed in inundation areas at lagoons behind the beaches and in bights which were separated from the sea. Coastal dunes develop where sand is deposited on the beach by currents and surf, transported by frequent strong onshore wind, and finally deposited behind dead or living barriers. They occur almost along the entire North Sea coast. At the German coast of the Baltic Sea, dunes are only locally developed.
In Form eines Zeit-Höhen-Diagramms werden die Höhenlagen ur- und frühgeschichtlicher Wohnniveaus in der Marsch zwischen Ems- und Elbemündung dargestellt. Es werden die Faktoren diskutiert, die bewirken, daß die gemessene Höhenlage der Wohnniveaus von der ursprünglichen Höhenlage abweicht. Die Wohnniveaus können als Marken für Höchstwasserstände gelten, und zwar sind die Wohnniveaus nur bestimmter Siedlungsschichten aussagekräftig, vor allem solcher, die einen Neubeginn der Besiedlung m einer Flachsiedlung oder auf einem Wurtauftrag markieren. Das Diagramm spiegelt die drei Siedlungsperioden in der nordwestdeutschen Marsch wider. Die Flachsiedlungen jeweils zu Beginn dieser Siedlungsperioden markieren einen Stillstand im Anstieg des Wasserspiegels. Die Wohnniveaus in gleichaltrigen Marschensiedlungen weichen in ihren Höhenlagen z. T. stark voneinander ab, da das Hochwasser in unbedeichter Marsch unterschiedlich hoch auffiel, je nachdem, wie weit die Entfernung zum offenen Meer war.