Predicting the effects of climate change on alpine rock slopes: Evaluation of paraglacial and periglacial drivers of rockfall in the European Alps
Final Report Abstract
The project aimed to quantify rockfall and to identify paraglacial and periglacial drivers of rockfall in two catchments in the European Alps. (1) The thermal regime affects rockwall stability. Rock temperature loggers were used to monitor the thermal regime of rockwalls between 2016 and 2019. The temperature data revealed a large influence of snow cover on the thermal regime that covered and insulated the rockwalls. Based on the temperature data and snow cover duration, regional rock permafrost distribution was modelled for the Hungerli and Gaisberg Valley. The models revealed a lower limit of permafrost between 2600 and 2700 m and mostly permafrost conditions at north-facing rockwalls above 2800 m. (2) Geotechnical measurements were conducted along monitored rockwalls and show higher rock mass strength at higher located rockwalls. Seismic measurements were used to quantify fracture density. Results showed that rockwalls have a higher fracture density as anticipated based on geotechnical measurements alone. Crackmeters were used to monitor fracture kinematics. They revealed thermal- and ice-induced dynamics at daily and annual scale with occurrence and magnitude influenced by snow cover. Laserscanning of north-facing rockwalls was performed annually and used to quantify rockfall volume and erosion rates. Result showed that erosion rates increased with altitude. (3) Freezing tests were conducted in the laboratory and revealed that ice stresses resulting from volumetric expansion are far below theoretical values, however, these stresses can exceed rock strength. Stresses developed by ice segregation experienced lower magnitudes and crack rock sub-critically. Frost cracking was modelled using measured rock temperature as input data. Frost cracking increases with altitude and physical based model results correspond better to fracture mapping. (4) Talus slope volumes were quantified using geophysics and used to calculate long-term erosion rates. These rates are half a magnitude higher to current erosion rates. (5) European Alps-wide erosion rates were compiled and used to put observed erosion rates into a larger context. Our data revealed an immediate increase of erosion following glacier retreat, which suggests that the ongoing rapid retreat of glaciers is likely to be associated with more rockfall. In addition, our data suggest that a lagged increase in erosion due to permafrost warming and continued frost weathering. In summary, both paraglacial and periglacial processes increase the erosion rate.
Publications
- (2017). Thermal and Mechanical Responses Resulting From Spatial and Temporal Snow Cover Variability in Permafrost Rock Slopes, Steintaelli, Swiss Alps. Permafrost and Periglacial Processes, 28(1), 140-157
Draebing, D., Haberkorn, A., Krautblatter, M., Kenner, R., & Phillips, M.
(See online at https://doi.org/10.1002/ppp.1921) - (2017). Thermo-cryogenic controls of fracture kinematics in permafrost rockwalls. Geophysical Research Letters, 44(8), 3535-3544
Draebing, D., Krautblatter, M., & Hoffmann, T.
(See online at https://doi.org/10.1002/2016GL072050) - (2018). Divergence, convergence and path-dependency of paraglacial adjustment of alpine lateral moraine slopes. Land Degradation & Development, 29(6), 1979-1990
Draebing, D., & Eichel, J.
(See online at https://doi.org/10.1002/ldr.2983) - (2018). From active to stable: Paraglacial transition of Alpine lateral moraine slopes. Land Degradation & Development, 29(11), 4158-4172
Eichel, J., Draebing, D., & Meyer, N.
(See online at https://doi.org/10.1002/ldr.3140) - (2019). Rock slope instability in the proglacial zone: State of the Art. In: Heckmann, T. & Morche, D. (Eds.), Geomorphology of proglacial systems - Landform and sediment dynamics in recently deglaciated alpine landscapes Heidelberg, Springer: 119-141
McColl, S. T., & Draebing, D.
(See online at https://doi.org/10.1007/978-3-319-94184-4_8) - (2019). The Efficacy of Frost Weathering Processes in Alpine Rockwalls. Geophysical Research Letters, 46(12), 6516-6524
Draebing, D., & Krautblatter, M.
(See online at https://doi.org/10.1029/2019GL081981) - (2020): Geomorphology and geological controls of an active paraglacial rockslide in the New Zealand Southern Alps. Landslides 17: 775-776
Cody, E., Draebing, D., McColl, S.T., Cook, S.J., Brideau, M.A.
(See online at https://doi.org/10.1007/s10346-019-01316-2) - (2020): UAV-based detection of turf-banked solifluction lobe movement and its relation to material, thermal and vegetation controls. Permafrost and Periglacial Processes 31(1):97-109
Eichel, J., Draebing, D., Kattenborn, T., Senn, J., Klingbeil, L., Eling, C., Wieland, M., Heinz, E.
(See online at https://doi.org/10.1002/ppp.2036)
