Sea ingression dynamics and its interaction with occupation of the Lowlands between AD 300 and 1000

The Early Middle Ages (ca. 300 - 1000 AD) was a period of severe pan-European economic and demographic change. During this period population declined and human influence on the landscape diminished throughout large parts of Europe (Cheyette 2008). Traditionally archaeologists and historians regard these Early-Medieval developments as the result of cultural processes. However, recent reconstructions show frequent climate fluctuations (Büntgen et al. 2011) and dramatic landscape changes in the Netherlands for this period (Vos & Van Heeringen 1997; Stouthamer et al. 2011). This suggests that economic and demographic changes might not be induced by cultural processes only, but also by climate and landscape dynamics (e.g. riverflooding, sea ingressions). To determine how and to what extent environmental changes contributed to the Early-Medieval economic and demographic changes, the ‘The Dark Ages in an interdisciplinary light’ project was initiated. As part of the project, this contribution shows the landscape dynamics of the Dutch coastal area during the Early Medieval period. In this geomorphological dynamic region, major sea ingressions occurred forming large tidal inlets. Occupation in this region mainly occurred in the supratidal environment, e.g. on dwelling mounds (Vos & Gerrets 2005) and was most likely influenced by these landscape dynamics. Development of the geomorphological elements of these tidal systems (channels, tidal flats and salt marshes) is extensively mapped in a GIS and coupled to a database storing information on age of the tidal system and its individual geomorphological elements. This generates a new integrated overview of the development of tidal systems for every possible time step. Palaeogeographical maps can be derived and the GIS provides the possibility to statistically analyse sea ingression dynamics in the Early Middle Ages and how this differs from other periods of sea level highstand (~last 3000 years). By comparing these maps with archaeological data, possible connections between cultural dynamics and landscape changes can be discovered. At the onset of the Early Middle Ages, first results suggest silting up of former estuaries, both in the western part and the northern part of the Netherlands. Meanwhile, large scale extension of tidal systems at the expense of habitable land occurred in the SW part of the Netherlands (Vos & Van Heeringen 1997). Adversely, at the end of the Early Middle Ages, some large sea ingressions took place in the northern part of the Netherlands (Middelzee, Lauwerszee), while the SW part of the Netherlands mainly silted up (Van der Spek 1995). In a later phase of this research, the extensive dataset allows thorough comparison with archaeological data (e.g. development of dwelling mounds, large scale peat drainage) and comparison between different coastal regions. Besides, it forms a tool for site selection to perform more detailed research (fieldwork and dating) to better pinpoint the relation between geological and archaeological events.