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Abstract. River channel patterns may alter due to changes in hydrological regime related to changes in climate and/or land cover. Such changes are well documented for transitions between meandering and braiding rivers, whereas channel pattern changes between laterally stable and meandering rivers are poorly documented and understood. We hypothesize that many low-energy meandering rivers had relatively low peak discharges and were laterally stable during most of the Holocene, when climate was relatively stable and human impact was limited. Our objectives in this work are to identify a Late Holocene channel pattern change for the low-energy Overijsselse Vecht river, to develop and apply a novel methodology to reconstruct discharge as a function of time following a stochastic approach, and to relate this channel pattern change to reconstructed hydrological changes. We established that the Overijsselse Vecht was laterally virtually stable throughout the Holocene until the Late Middle Ages, after which large meanders formed at lateral migration rates of about 2 m yr−1. The lateral stability before the Late Middle Ages was constrained using a combination of coring information, ground-penetrating radar (GPR), radiocarbon (14C) dating, and optically stimulated luminescence (OSL) dating. We quantified bankfull palaeodischarge as a function of time based on channel dimensions that were reconstructed from the scroll bar sequence and channel cut-offs using coring information and GPR data, combined with chronological constraints from historical maps and OSL dating. We found that the bankfull discharge was significantly greater during the meandering phase compared to the laterally stable phase. Empirical channel and bar pattern models showed that this increase can explain the channel pattern change. The bankfull discharge increase likely reflects climate changes related to the Little Ice Age and/or land use changes in the catchment, in particular as a result of peat reclamation and exploitation.

Abstract. Identifying lateral migration rates of meandering rivers is relevant both for fluvial geomorphology and to support river management. Lateral migration rates for contemporary meandering systems are often reconstructed based on sequential remote sensing images or historical maps, however the time frame for which these sources are available is limited and hence likely to represent fluvial systems subjected to human influence. Here, we propose to use scroll bar sequences as an archive to look further back in time using optically stimulated luminescence (OSL) dating of sand-sized quartz grains. We develop a modelling procedure for the joint Bayesian analysis of (OSL) dating results and historical map data. The procedure is applied to two meanders from the Overijsselse Vecht, a medium-sized sand-bed river in The Netherlands. We obtained 9 samples for OSL dating from scroll bars, and combined OSL dating results with historical map data for the period 1720–1901 AD. The procedure we propose here incorporates strengths of both data types for reconstructing fluvial morphodynamics over longer timeframes. Using an iterative modelling approach, we translate spatial uncertainty of historical maps into temporal uncertainty of channel position required for Bayesian deposition modelling. Our results indicate that meander formation in the Overijsselse Vecht system started around 1400 AD, and lateral migration rates were on average 2.6 and 0.9 m/y for the two investigated bends, until river channelization around 1900 AD.

Abstract. River channel patterns may alter due to changes in hydrological regime, related to changes in climate or land cover. Such changes are well documented for transitions between meandering and braiding rivers, whereas channel pattern changes between laterally stable and meandering rivers are poorly documented and understood. We identified a river that was laterally almost stable throughout the Holocene until the Late Middle Ages, after which large meanders formed at lateral migration rates of about 2 m yr−1. The lateral stability before the Late Middle Ages was proven using a combination of coring information, ground-penetrating radar (GPR), radiocarbon (14C) dating, and optically stimulated luminescence (OSL) dating. Our objective of this work is to identify the possible causes for the meander initiation. We carried out a unique reconstruction of bankfull discharge as a function of time, based on channel dimensions that were reconstructed from the scroll bar sequence using coring information and GPR data, combined with chronological constraints from historical maps and OSL dating. Empirical channel and bar pattern models were used to determine the potential for meandering and to identify the causes of meander initiation. Several potential causes were investigated, varying from discharge regime changes to increased sediment input. Our investigation shows that bankfull discharge was two to five times higher during the meandering phase compared to the laterally stable phase. This increase likely reflects climate changes related to the Little Ice Age and land use changes in the catchment, in particular as a result of peat reclamation and exploitation. We hypothesize that many low-energy meandering rivers were laterally stable during most of the Holocene, reflecting relatively low peak discharges during a stable climate and with limited human impact. However, channel deposits associated with such stable phases are poorly preserved, due to recent increase in dynamics of such systems. Considering the importance of climate and land use changes on the river channel pattern, successful river restoration requires an integral approach that includes scenarios of climate and land use changes in the catchment.

Past studies of archaeological bog finds, such as bog bodies, wooden trackways and a wide variety of other materials, are characterized by a strong focus on material culture. Their original environmental and cultural context has received far less attention. This paper centres on the original landscape setting of bog bodies. Interdisciplinary reconstructions of the physical and cultural landscape at the time of deposition can lead to significant new and more detailed insights into the context and meaning of this remarkable phenomenon. We aim to show the value of such interdisciplinary research by reconstructing the original physical and cultural landscape setting of the most iconic bog body of The Netherlands: Yde Girl. This approximately 16-year-old girl was killed about 2000 years ago and deposited in a bog south of the modern-day village of Yde (province of Drenthe). Our interdisciplinary research team used a combination of research methods from physical geography, geomorphology, palynology and archaeology to analyse both the site itself and its wider environment. This kind of integrated, detailed landscape research on bog bodies has hardly been done yet. We expect that our research design, methodology and results may also be applied in future research of other bog bodies. Furthermore, they may inspire research on other types of archaeological find categories from peatlands.