This study presents an annually resolved dendrochronological reconstruction of hydrological impacts on the Roman and early-medieval landscape in the Low Countries of northwestern Europe. Around 600 hydrologically sensitive ring-width patterns, mostly oak (Quercus robur/petraea) as well as some ash (Fraxinus excelsior) and elm (Ulmus sp.), were selected from an initial dataset of >5000 and compiled into two chronologies that span the first millennium AD. Their content and (dis)similarities to established tree-ring chronologies from this and surrounding regions were used to assess their provenance, which in both cases is in the area where the majority of the wood was recovered. Instances of high groundwater levels and/or inundation were catalogued by identifying multi-year intervals of strongly reduced annual growth that occurred simultaneously throughout the research area. The resulting record contains 164 events dated between AD 1 and 1000, of which 21 have a recurrence frequency ≥50 years. One-third of the ≥50-yr events date between AD 185 and 282, making this the most flood-intense interval of the first millennium. The severest reconstructed impact of the first millennium dates to AD 602. A comparison to historically documented river floods/sea breaches and drought/heat spells shows that the predominant cause of the inferred impacts in the research area was river overflow. Synchronous inundation responses of oaks preserved in former bogs in Lower Saxony (NW Germany) indicate that half of the reconstructed events occurred on a supra-regional level, pointing to regional precipitation as a main forcing. River floods documented in written sources do not seem to have affected tree growth in Lower Saxony in a significant manner, indicating that the majority of documented floods most likely were caused by hydrological circumstances upstream of the catchments of the Rhine and/or Meuse. Reconstructed flood impacts during the Early Middle Ages coincide remarkably well with construction and repair of Rhine revetments at the early-medieval site of Leiderdorp-Plantage in the western Netherlands.

The first millennium AD encompasses the Roman period (12 BC to AD 450) and the Early Middle Ages (AD 450 to 1050). In the Netherlands, this millennium saw population growth, steep decline and subsequent revival. In addition, many changes occurred in the physical landscape, marking a transition from a mainly natural prehistorical lowland landscape to an increasingly human-affected landscape. This paper synthesises the main landscape changes and human–landscape interactions in the Netherlands during this dynamic period. The degree of landscape change is compared between the coastal plain, the delta and the Pleistocene sand area.

Human activities caused major often unintended geomorphological changes in all studied landscapes. Landscape sensitivity to human impact, however, strongly varied as a function of preceding landscape state. The most prominent changes took place in many parts of the coastal plain, where back-barrier peatlands transformed into open tidal basins. Presence of compaction-prone peat and intensified artificial drainage led to subsidence. This precondition and slow anthropogenic forcing combined, made the area more sensitive to stochastically occurring storms, which could serve as tipping points for large-scale drowning. Eventually, major peatlands turned into tidal areas that for many centuries would remain unsuitable for habitation. Human-induced peatland subsidence also led to the formation of the new Hollandse IJssel and Lek river branches. This marked a major reorganisation of the river network in the lower Rhine–Meuse delta. In the middle and upstream parts of the delta, the landscape was more stable. Yet, settlements on the natural levees show adaption to increasing flooding frequency from the Late Roman period onwards. The settlements shifted towards higher positions, while route networks between them largely remained intact. Smaller-scale landscape changes were found in the Pleistocene sand area. Here, local sand drifting occurred, most frequently occurring close to human movement corridors. Drift sand intensity became larger as population density increased after c.AD 900.

The results from analyses of botanical remains (pollen, wood, charcoal, seeds) from several archaeological features excavated in Kluizen (northern Belgium) are presented. The region was largely uninhabited until the Iron Age and Roman period when a rural settlement was established, resulting in small-scale woodland clearance. The site was subsequently abandoned from c. AD 270 till the High Middle Ages. The results of the archaeological and archaeobotanical analyses provide information on changes in land use and resulting dynamics of woodland cover and composition between c.600 BC and AD 1200, with a spatial and temporal resolution unrivalled in northern Belgium. Especially the long period of woodland regeneration following abandonment of the site around AD 270, covering the Late Roman and Early Medieval period, could be reconstructed in detail. Abandoned fields were first covered with pioneer woodland (Salix, Corylus and Betula), then Quercus-dominated secondary forest and finally a late-successional forest with Fagus sylvatica, Carpinus betulus and Ilex aquifolium, an evolution that took over 300 years. The results also indicate that the observed increase of Fagus during the Early Middle Ages, which was never an important element in the woodland vegetation in northern Belgium before, was related to climatic changes rather than anthropogenic factors.

This paper focuses on unravelling the 1st millennium AD in the present-day Netherlands and the applicability of modelling when studying the past. By presenting the results of several studies analysing changes (or persistence) in connectivity and habitation patterns, the significance of these findings for (spatial) modelling is derived. The transition between the Roman and early-medieval periods is particularly interesting in this respect as it is characterised by severe pan-European political, socio-economic and demographic changes. Additionally, recent studies in geosciences increasingly point to marked climatic and landscape changes, such as river avulsions and floods, occurring at the same time. The extent to which these environmental and cultural dynamics were entwined and mutually influential is generally unknown, especially on larger-scale levels. Lowlands, such as the Netherlands, are especially suited to study these complex interactions since boundary conditions, i.e. the set of conditions required for maintaining the existing equilibrium in a region, in such areas are particularly sensitive to change.

In this paper the combined results of several recently developed landscape-archaeological models are presented. These models spatially analyse natural and cultural dynamics in five manifestations: route networks, long-distance transport, settlement patterns, palaeodemographics and land-use systems. Combined, these manifestations provide information on connectivity, persistence and habitation, key concepts for the cultural landscape as a whole. Results show that only by integrating these modelling outcomes is it possible to reconstruct boundary conditions and high-resolution spatio-temporal frameworks for cultural-landscape change. Equally, these models invite reflection on their applicability and, as such, point to the need for new theoretical framing and the development of more multi-proxy, evidence-based and transdisciplinary research approaches in archaeology. The evident interrelationship between cultural and natural-landscape dynamics necessitates a more integrated and transparent research attitude, covering multiple scales and studying the cultural landscape as a whole. Only then can models reflect historical reality as closely as possible.

Variation in human activities has greatly impacted the processes and intensities of erosion, sediment transport and storage throughout the Late Holocene, and many lowland rivers around the world have responded to these variations. Although this long-term process–response relationship has been established before, the effects of short-term (c.200-year) changes in human impact on lowland rivers are less well studied. Here, we followed an integrated approach whereby observations of floodplain changes are evaluated against detailed data on human impact for three lowland rivers in the Belgian loess belt: Dijle, Mombeek and Gete rivers. Pollen data were used to reconstruct changes in local and regional vegetation and to calculate human impact scores. Corings along transects and a database of c.160 radiocarbon ages were used to reconstruct geomorphic changes in the river valleys. Our results show a decrease in human impact between 200 and 800 AD, which can be related to the decreased population density in Europe during the first millennium AD. During this period, forests in the studied catchments regenerated, soil erosion decreased, hillslope–floodplain connectivity decreased due to the regeneration of valley-side vegetation barriers, and sediment input in the floodplain decreased. A reaction to this decreased human impact can be observed in the river valleys during the first millennium AD, with a regrowth of the alder carr forest and an increase in the organic matter content of the alluvial deposits with a local reactivation of peat growth. The observed trajectories of Belgian river valleys during the first millennium AD provide more insight into the sensitivity of these river valleys to short-term variations in human impact. These results can in turn be used to better estimate the effects of future changes in the catchments on the fluvial system.