Kleiner Piz Buin/Piz Buin Pitschen: experimental investigations

Rockfalls, rockslides, and debris flows are gravitational mass movement processes, which frequently occur in alpine regions. The Alpine Remote Sensing Group at the SLF develops and utilizes different methods to ensure an early detection of such instabilities. With various different methods, the movements of rocks and slopes can be identified and observed. However, predicting the release moment of mass movements is difficult, and in some cases even impossible.

Currently, the SLF is observing a potential instability at the Piz Buin Pitschen, which, if released, could become dangerous to mountaineers. The popular route to the Grossen Piz Buin (3312m) in the Silvretta Range starts on the Austrian site and leads over the Ochsentaler Glacier and past the Kleiner Piz Buin (Piz Buin Pitschen, 3255m). Since a few years, frequent rockfall has been observed in the region of the Buinlücke. During an inspection in July 2020, scientists from the SLF discovered a strongly cragged and deformed rock mass with a crown fracture near the summit of Kleiner Piz Buin. The presence of permafrost, which could have been affected by the warmer temperatures of the last few years, is being observed and recorded.

Evolution of the moving rock mass on the Kleiner Piz Buin/Piz Buin Pitschen (2009 (left). 2020 (middle) and 2022 (right)). Captured from the Piz Buin Grond looking southwest. Photos: SAC Tourenportal / Gregor Ortner, SLF

First measurements in August 2020

In August 2020, the first helicopter observation flight and drone-based photogrammetric survey took place. After geologic modeling and an evaluation of the digital terrain models and orthophotos, first estimates of the possible release volume were made. Two scenarios were taken into consideration:

• A rockslide with an assumed volume of >100’000 m3
• An extreme, unlikely rock avalanche of > 1 Mio. m3

Simulations with these volumes were performed using RAMMS (Rapid Mass Movement Simulation), a software developed by the SLF, to gain first insights on the hazard potential. Subsequently, the mountain cabins in the surrounding areas and the responsible authorities were informed about the results.

Since then, the SLF has conducted an inspection and a remote sensing campaign once a year to record potential changes. Volume loss and rock displacements have been observed, and certain rock parts moved more than a meter a year downslope. The debris pile at the foot of the Piz Buin Pitschen has grown every year, which indicates frequent rockfalls. The SLF has informed the responsible authorities, the cabins and the Swiss and Austrian Alpine Club about the research results.

Planned Research

The increasing climate change and the associated changes in alpine regions prove further research at the Kleiner Piz Buin as particularly relevant, especially because a moving rock mass can be studied prior to its potential release. Apart from the continuing measurements, additional measurements with radar data, and, if necessary, installations of seismic monitors on-site are planned. The monitoring of such potential instabilities is one of the research focuses of the newly created research center CERC (Climate Change, Extremes and Natural Hazards in Alpine Regions Research Center) at the SLF.