Rainfall-triggered flood events represent a major societal and economic threat for Central Europe. However, knowledge about their spatio-temporal variability and connection to climatic changes in the past is still limited, leaving uncertainties about flood occurrence under future climate change scenarios. Instrumental and documentary records of past floods are usually too short to reliably assess their natural variability, but lake sediments with flood-generated detrital event layers have been shown to be suitable in providing long and precisely dated flood records, enabling important insights into the natural recurrence frequency, regional distribution and climatic triggers of extreme floods. Nevertheless, the spatial coverage of such lake sediment palaeoflood records across Central Europe is still very heterogeneous with only very few existing in the Eastern Alps. The resulting uncertainties about past flood activity in this region are particularly invidious as flooding in river catchments located there (e.g. Danube, Elbe) is likely to affect large parts of Central and Southeastern Europe.
This project aims at establishing a new palaeoflood record for the Eastern Alps by investigating the sedimentary record of Hallstätter See (Austria). As revealed by a pilot study, the lake sediments contain frequent detrital layers, which are related to the input of allochthonous material during flood events of the Traun, a major tributary of the Danube. New lake sediment cores raised from Hallstätter See will be investigated regarding the occurrence of detrital flood layers by combining sediment microfacies analysis on large-scale thin sections with high-resolution µ-XRF scanning. With a robust chronology established via microscopic varve counting and radiocarbon dating, this will finally yield a long (>5000 years) and precisely dated record of flood activity in the Eastern Alps, which will be compared with other regional palaeoflood records in terms of identifying common patterns and trigger mechanisms of past flood events. The improved understanding of the spatio-temporal variability of past flood activity in Central Europe and the flood-generating processes will allow a more reliable assessment of future flood scenarios.
Project title: Sediments of Hallstätter See as a palaeoflood archive (FWF M 1907 Meitner-Programm). Duration 2016-2018.
P.i.: Stefan Lauterbach
Co-P.i.: Christoph Spötl
External collaborators: Achim Brauer (GFZ Potsdam)