Tracing the Anthropogenic Fingerprint: Sedimentological and Isotopic Insights into Vienna’s Floodplain Archives

Human impact has developed into a major external forcing control on Earth’s environmental and geological processes, yet our understanding of the magnitude of its impact and evolution, particularly in (peri-)urban settings, is still limited. This study investigates the anthropogenic impact of the metropolis Vienna on its peri-urban environment in floodplain archives of the Danube River. By applying sedimentological, geochronological and chemostratigraphic methods, we aim to characterise the interplay between upstream human interventions and local river dynamics, and to identify and evaluate the geological signal of the Great Acceleration since the 1950s downstream of Vienna.

The study area is located in the National Park Donau-Auen, where minimal direct human intervention allows quantifying the human stratigraphic fingerprint and testing event-based dating using (artificial) radionuclides in an alluvial setting. Flood deposit ages were successfully determined combining radiogenic nuclide concentrations (¹³⁷Cs, ²³⁹Pu, ²⁴⁰Pu, ²³⁷Np, ²³³U, ²³⁶U), field sedimentological methods, and historical records. Preliminary results reveal three distinct sedimentation periods reflecting upstream human interventions. The first phase (1870 – 1954) aligns with extensive river channelization leading to rapid erosion of mid-channel bars and backwater aggradation. The second phase (1954 – 1991) shows laterally extensive and thick sandy flood deposits from fast and undamped sediment transport through the straightened riverbed during extreme events. The final phase (1991 – 2002) is characterized by the thick, silty, and seemingly structureless flood deposits, interpreted as remobilized sediment from barrier lakes since the construction of the nearby hydro-power station Freudenau in 1997.