Project Details
Projekt Print View

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

Subject Area Physical Geography
Term from 2016 to 2020
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 316624774
 
Final Report Year 2021

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

 
 

Additional Information

Textvergrößerung und Kontrastanpassung