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.