Abstract ID: 28.7294 | Accepted as Poster | Poster | 2025-02-27 13:00 - 14:30 | Ágnes‐Heller‐Haus/Small Lecture Room

Rockfall events pose a danger for people and infrastructure in high mountain areas and have been suggested to intensify with human-induced global warming. However, longer-term datasets on rockfall activity are sparse and often biased regarding detection and hence their relation to climate is not that conclusive. This study applies a novel approach, using annual isochrones at the Witenwasserengletscher (UR) to reconstruct rockfall activity over the past century and to thereby investigate the potential influence of climate on rockfall activity. Through the analysis of melted out isolated debris patches from aerial imagery, a time series of rockfall events was extracted. Additionally, the size, volume, and location of the breakout zone of each event were determined. A total of 27 events could be identified between 1913 and 2014, mainly originating from one part of the headwall consisting of Zentraler Streifengneis. In general, the rockfall event volumes were relatively small and varied widely, with volumes ranging from 1 to 561 m3. While no significant long-term trend in rockfall activity was observed, periods of increased activity generally correlated with peaks in summer temperatures. Further, distinct periods of 5 to 10 years duration with no rock fall activity were observed and seem to fall into colder periods. However, no direct relationship between extreme rainfall and rockfall events was found. Comparison to the rockfall database of PERMOS from the Swiss Alps revealed a similar temporal pattern, despite the events being much larger and distributed all over Switzerland. Our approach of using debris deposits on glaciers as archive for rockfall activity shows clear potential but substantial uncertainties remain from the ambiguous identification of isochrones and their allocation to an absolute year. Overall, our century long reconstruction suggests that rockfall activity is likely influenced by high temperatures and may consequently further increase with rising temperatures in the future.