Alpine Rock Slopes

Project: Predicting the effects of climate change on alpine rock slopes: Evaluation of paraglacial and periglacial drivers of rockfall in the European Alps  (AlpineRockSlopes)

Project description: Rockfall from alpine rockwalls represents a hazard to human life and infrastructure but also a natural process of rock slope evolution. Two contrasting hypotheses currently exist which aim to explain rock slope evolution: (1) a paraglacial adjustment of the rockwalls with increasing frequency due to deglaciation and a subsequent asymptotically decline of adaption and (2) a frost-weathering dominant adaption with steady-state rates. Climate change will affect alpine systems by an increase of temperatures and a decrease of frost weathering activity and glaciated area. Hypothesis (1) suggests an increase of rockfall frequency due to deglaciation. On contrary, hypothesis (2) expects a decrease of rockfall frequency due to the dislocation of highest frost cracking activity to higher altitudes. Both hypotheses are based on assumptions which have been never tested or validated in the field. As a consequence, the future adaption of rockwall to climate change is unknown.Very few studies focus on rockfall after deglaciation on different time scales. On the Holocene time scale, rockfall is relied to increase post glaciation. The findings are based on dating and derivation of erosion rates without incorporating mechanical or thermal rockwall properties. As a result, the observed increase cannot be traced back to paraglacial adjustment or frost weathering processes. On the contrary, rock slope erosion in recently deglaciating areas can integrate mechanical and thermal rockwall properties. However, the period to establish frequency-distributions is too short to draw conclusions on potential evolution due to climate change.This approach integrates Holocene and recent rock slope erosion in one investigation. The objectives of the study are (1) to quantify the thermal regime of the rockwalls, (2) to quantify the response of mechanical regime and establish a short-term erosion rate. Furthermore, the study will (3) increase the process understanding of frost weathering and (4) quantify long-term rock slope erosion. In a space-for-time substitution approach (5) a rock slope erosion model will be developed to bridge short-term and long-term rock slope failure. Fieldwork will take place in the Hungerli Valley, Valais Alps, and in the Gaisberg Valley, Ötztal Alps. State-of-the-art geomorphological, geotechnical and geophysical methods including refraction seismic tomography, electric resistivity tomography, terrestrial laserscanning, laboratory frost-weathering simulation and Be-10 dating will be combined to address the research objectives. Expected results include the temporal and spatial distribution of permafrost and frost weathering processes, the short-term adaption of rockwalls, an increase of understanding of frost weathering processes, a frost weathering model, a rock slope erosion model bridging short- and long-term rock slope erosion and the prediction of future rock slope evolution in the context of climate change and increased deglaciation.

Funding body: German Research Foundation (01.08.2016 ‐ 14.10.2020)

Projekt participants:

• Dr. Daniel Dräbing
  
• Till Mayer (Ph.D. student UBT)
  
  

National and international project partners:

• Dr Steven Binnie (University of Cologne)
• Dr Miriam Dühnforth (former LMU Munich, Bayerische Versicherungskammer)
• Benjamin Jacobs (Technical University of Munich)
• Prof. Dr. Michael Krautblatter (Technical University of Munich)
• Dr. Samuel T. McColl (Massey University, NZ)
  
  

Publications:

• Draebing, D., Mayer, T., Jacobs, B., McColl, S. (accepted ): Alpine rockwall erosion patterns follow elevation-dependent climate trajectories. Communications Earth & Environment. doi: 10.21203/rs.3.rs-134858/v1
• Draebing, D., (2021): Identification of rock and fracture kinematics in high Alpine rockwalls under the influence of elevation. Earth Surface Dynamics 9:977-994. doi: 10.5194/esurf-9-977-2021
• Draebing, D., Mayer, T. (2021): Topographic and geologic controls of frost cracking in Alpine rockwalls. Journal of Geophysical Research - Earth Surface. doi: 10.1029/2021JF006163 
• Draebing, D., Krautblatter, M. (2019): The Efficacy of Frost Weathering Processes in Alpine Rockwalls. Geophysical Research Letters 46(12): 6516-6524. doi: 10.1029/2019gl081981
• McColl, S.T., Draebing, D. (2019): Rockslope instability in the proglacial zone: State of the Art. Invited book chapter to: Heckmann, T. & D. Morche (Eds.): Geomorphology of proglacial systems - Landform and sediment dynamics in recently deglaciated alpine landscapes. Springer Series, 119-141. doi: 10.1007/978-3-319-94184-4_8