Tracing Holocene sediment pathways in a Central European river catchment - the Weiße Elster (Central Germany)

The sediment dynamics include erosion, transport and deposition of sediments within and through a catchment. Erosion leads to a degradation of fertile soils on the slopes, while introducing large-scale inputs of fine-grained overbank sediments into floodplains. These sediments often contain particulate organic carbon and partly also contaminants. This sediment input changes floodplain properties, including e.g. geomorphology, habitat diversity, ecosystem services or human health impacts. Throughout most of the Holocene human activities increasingly influenced sediment dynamics in Central European river catchments through agriculture and settlement, starting in the Neolithic and strongly accelerating since the Middle Ages. However, the Holocene sediment dynamics of Central European river systems remains currently poorly understood. One key question concerns the fate of eroded slope sediments: How much is deposited within a certain part of the catchment, and how much is transported further downstream? Recent studies have addressed this issue by calculating Holocene sediment budgets including ‘sediment delivery ratios’ (SDRs), approximate estimations of the long-term fractions of eroded slope sediments reaching the channel or being transported to the catchment’s outlet. However, the ‘black box’ character of long-term SDRs prevents a detailed examination of temporal variations. Sediment provenance analyses could overcome this limitation by more precisely tracing pathways of Holocene sediments through river systems. Furthermore, well-resolved spatio-temporal information about former human activities has often been unavailable, limiting our ability to estimate human influence on the sediment dynamics.

We applied a comprehensive multi-disciplinary approach to the Weiße Elster catchment in Central Germany, which has been partly settled since the Neolithic. Our approach encompassed geomorphology, geophysics, geochronology, geochemical analysis, soil erosion modelling, settlement archaeology and history. We compared patterns and provenance of floodplain sediments in the middle and upper reaches and of colluvial deposits along the middle river reach with regional settlement history. This allowed us to identify the origin of the fluvial sediments in the middle river reach, and evaluate the diachronic influence of human activities on the Holocene sediment dynamics in the floodplain.