Massive sediment pulses triggered by a multi-stage alpine cliff fall (Hochvogel, DE/AT)

Abstract

Abstract. Massive sediment pulses in catchments are a key alpine multi-risk component. Substantial sediment redistribution in alpine catchments frequently causes flooding, river erosion, and landsliding, and affects infrastructure such as dam reservoirs as well as aquatic ecosystems and water quality. While systematic rock slope failure inventories have been collected in several countries, the subsequent cascading sediment redistribution is virtually unaccessed. This contribution reports for the first time the massive sediment redistribution triggered by the multi-stage failure of more than 150,000 m3 from the Hochvogel dolomite peak during the summer of 2016. We applied change detection techniques on seven 3D-coregistered high-resolution true-orthophotos and digital surface models (DSM) obtained through digital aerial photogrammetry later optimized for precise volume calculation in steep terrain. The analysis of seismic information from surrounding stations revealed the temporal evolution of the cliff fall. We identified the proportional contribution of > 600 rockfall events (>1 m3) from 4 rock slope catchments with different aspects and their volume estimates. In a sediment cascade approach, we evaluated erosion, transport, and deposition from the rockface to the upper channelized erosive debris flow channel, then to the widened dispersive debris flow channel, and finally to the outlet into the braided sediment-supercharged Jochbach river. We observe the decadal flux of more than 400,000 m3 of sediment with massive sediment pulses that (i) respond with reaction times of 0–4 years and relaxation times beyond 10 years, (ii) with faster response times of 0–2 years in the upper catchment and more than 2 years response times in the lower catchments, (iii) the inversion of sedimentary (102–103 mm/a) to massive erosive regimes (102 mm/a) within single years and the (iv) dependency of redistribution to rainfall frequency and intensity. This study provides generic information on spatial and temporal patterns of massive sediment pulses in highly-charged alpine catchments.

How water, temperature and seismicity control the preparation of massive rock slope failure (Hochvogel, DE/AT)

“…This flank shows frequent failure of rock towers, as for example a 130,000 m 3 rockfall in 2016 (Fig. 2a-B, Barbosa et al (2023)). The site https://doi.org/10.5194/egusphere-2024-231 Preprint.…”

“…Massive rock slope failures are an important geomorphic hazard that causes increasing risk in the wake of climate change and population growth (Lacasse and Nadim, 2009;Picarelli et al, 2021). To prevent damage to people or property, the anticipation of such events becomes highly crucial (Sättele et al, 2016;Chae et al, 2017;Pecoraro et al, 2019;Leinauer et al, 2023), and thus, relevant drivers and potential triggers of imminent failures must be identified and understood. Exploiting the available data of comprehensive monitoring and early warning systems to gain understanding of all relevant pre-failure process dynamics should therefore become a standard procedure (Gischig et al, 2016).…”