Research
My primary interests are the geomorphic processes that shape the earth’s surface. I work at a range of temporal and spatial scales from detailed examinations of weathering processes on rock samples in the laboratory to the monitoring of rock slope adjustment in high alpine valleys. The theme of my research is erosion and sedimentation processes such as paraglacial adjustment due to deglaciation and periglacial rock slope and hillslope processes influenced by climate change. I use a spectrum of research approaches, including geomorphological, geophysical and geotechnical field observations, physical modelling in laboratories, and development of theoretical and physical models.
Paraglacial Rock slope Failures
Alpine landscapes are affected by ongoing and past glaciations and paraglacial readjustment conditioned by former glaciations. As a response to climate change, an elevated geomorphological activity associated with glacier retreat is expected, however, this paraglacial increase of geomorphic processes is currently poorly understood. In my research, I focus on paraglacial rock slope failures ranging from small-scale rockfall to large-scale rock flow.
Invited review book chapter on paraglacial rock slope failures [abstract]
Paper on thermal and mechanical interaction on permafrost-affected rockwalls [abstract]
Paper on geomorphology and geologic controls of the Mueller Rockslide [Full Text]
Paper on rockwall erosion driven by climatic processes [Full Text]
Permafrost Rockwalls
Field evidences of ice in rock scarps and rockfall talus slopes indicate that permafrost is involved in alpine rock slope processes. With regard to climate change in mountain areas, there is a pressing need to estimate the stability of permafrost-affected rock walls, thus, these rock walls are often located above hydropower reservoirs, glacial lakes or ski fields and present hazards to infrastructure and humans. Unfortunately, the involvement of permafrost and periglacial processes in rock slope instability is poorly understood. The goals of my research are to understand (1) how permafrost affects rock wall stability, (2) how weathering processes influence rock slope erosion and (3) how rock walls will develop in a warming and deglaciated future.
Paper on thermal and mechanical interaction in permafrost-affected rockwalls [Abstract]
Paper on water flow in fractures [Abstract]
Paper on snow cover and its influence on permafrost [Full Text]
Paper on kinematics of permafrost-affected rockwalls [Full Text]
Paper on rockwall erosion driven by climatic processes [Full Text]
Weathering Processes
Frost weathering is assumed to be the dominant weathering process in Alpine rockwalls. Using laboratory tests on rock samples of four different lithologiues, we show that both volumetric expansion and ice segregation can cause ice stresses in rock slopes, however, preconditions for volumetric expansion are seldom fulfilled. Frost weathering processes cause ice stresses below tensile strength of rocks, ice stress intensities are mostly below estimated fracture toughness. Therefore, we conclude that frost weathering occurs via subcritical cracking. In my research, I use my findings to adjust and develop numerical frost cracking models.
Paper on the efficacy of frost cracking in Alpine rockwalls [Full Text]
Paper on topographic and geologic control on frost cracking in Alpine rockwalls [Full Text]
Paper on thermal and frost weathering processes in Alpine environments [Full Text]
Paper on rockwall erosion driven by climatic processes [Full Text]
Paraglacial Adjustment of Hillslopes
In hillslope systems, paraglacial adjustment is assumed to be completed under a vegetation cover. We investigate the feedbacks between vegetation and solifluction processes. We show that once process magnitude and frequency sufficiently decreases, ecosystem engineer species (e.g. Dryas octopetala) can establish and actively change the dominant processes from linear erosion and slope wash to solifluction. This interaction between vegetation and solifluction contributes significantly to paraglacial sediment reworking, even after vegetation colonization.
Solifluction Processes
Solifluction lobes are widespread landforms in alpine and arctic environments. Most work up to date focused on solifluction movement and inherent soil mechanics. However, the influence of vegetation on solifluction lobes was seldom incorporated in the investigations. We investigate young turf-banked solifluction lobes (<80 years) with high risers (>1 or 2 m) and try to quantify the interaction between vegetation and landforms. Furthermore, we try to identify the role of vegetation on solifluction lobe genesis and dynamics.
Refraction Seismics
Many problems in cryospheric environments are associated with permafrost thaw or degradation and concern subsurface properties and processes that occur below the surface. To approach these problems, techniques are required to identify or quantify these subsurface processes or properties. In cooperation with Prof Krautblatter (TU Munich), I developed a cost-effective alternative refraction seismic approach. I investigated the seismic behavior of low-porosity rock samples during simulated permafrost conditions in the laboratory. The laboratory results were used for calibration of 3D SRT from my diploma thesis to monitor active-layer thaw in Steintaelli. The application of refraction seismics in periglacial environments is reviewed and the differentiation of active-layer, permafrost and bedrock layer of different landforms is quantitatively analyzed. Results show that refraction seismic can differentiate these layers in rock glaciers and ice-cored moraines, however, an additional geophysical technique such as Electrical Resistivity Tomography (ERT) is required for layer differentiation in talus slopes and debris-covered slopes.