Flash Flood Monitoring in Vienna, Austria (FlaMoVie)

From September 12-20, 2024 heavy rainfall events and massive flooding occurred in Austria due to the low-pressure system "Boris". Lower Austria and Vienna were severely affected by flooding and associated on- and off-site impacts. Flash flood discharge values in Vienna's torrent systems were particularly extreme – some experiencing a 1000-year event magnitude. It is evident that heavy precipitation events have shown a clear increasing trend in recent decades due to climate change, and these events are highly likely to continue to increase in the future, in some cases with still unforeseeable consequences. The project FlaMoVie (Flash Flood Monitoring Vienna, 2024–2026) is dedicated to (i) investigate the causes, course, and potential consequences of flash flood events in Viennese torrent catchments, and (ii) assess the determination of associated hydrological and geomorphological effects (incl. different climate change scenarios) using a hydro-geomorphological monitoring and modelling approach. In this contribution, we will highlight some monitoring results derived from multi-temporal Terrestrial Laser Scanning, field mapping/measurements, and hydrometeorological gauge data of the Alsbach system, i.e. a ca. 2 km² large flash-flood-prone, densely forested, torrential catchment in the northwest of Vienna, Austria. Field data is further integrated in CAESAR-Lisflood landscape evolution modelling using yielding high-resolution rates of erosion and sedimentation across the catchment. The investigations at the Alsbach allow to deduce important implications for the hydro-geomorphological response to torrential rainfall in forested small-scale headwaters in Viennese torrent catchments.