Characterizing Rockwall Weathering from Microclimate, Rock Moisture and Rockfall Acitvity – ClimRock

• Applicants: Dr. Daniel Dräbing; Professor Dr. Oliver Sass
• Subject Area: Physical Geography
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 426793773

Rock breakdown by weathering is the first step of the alpine sediment cascade. Weathering processes are influenced by diurnal heating and cooling, wetting and drying, diurnal and seasonal freezing and thawing or seasonal active-layer thawing. Individually or in combination, these processes result in the subcritical or critical propagation of fractures that act to prepare and trigger rockfalls. Rockfall processes are a key agent of alpine landscape evolution but also present hazards to tourists and infrastructure. Nonetheless, thermal- and moisture-driven weathering processes are poorly understood and particularly, temporal and spatial information on moisture in rockwalls are lacking. Improved process understanding is necessary to anticipate trajectories and rates of weathering processes and associated rockfall in light of foreseeable climate change. We follow a conceptual multiscale-model integrating temperature and precipitation/moisture gradients, which depend on elevation and aspect: (1) On laboratory scale, we will simulate temperature cycles, wetting and drying and frost weathering under controlled conditions to quantify cracking activity and develop temperature/moisture-cracking activity relationships, combining AE sensors, crackmeters, moisture and temperature probes and resistivity measurements. (2) On rockwall scale, the lack of information results partially from the difficulty to measure rock moisture in the field. We will monitor temperature, moisture and rock kinematics using temperature and self-developed moisture sensors, crackmeters and meteo stations. We will quantify spatial differences of rock moisture and temperature discontinuously using 2D resistivity surveys and IR photography. The limestone rockwalls in the Dammkar and Dachstein research areas were selected to cover an altitudinal range from 1400 to 3000 m and north and south faces. (3) We will use our results on laboratory and rockwall scale to model rock weathering on mountain scale, applying already tested GIS-based geostatistical and rock mechanical models and simulation tools, to overcome the limitations of currently used purely temperature-driven models. We will compare the results with rockfall data that we will create from repeated Terrestrial Laserscanning surveys. Furthermore, we will adjust our temperature conditions to simulate weathering condition during the Little Ice Age and in 2050 and 2100 by incorporating climate scenarios. The novelty of this project is the investigation of rock weathering across spatial scales, addressing process interactions and integrating rock moisture and rock-mechanical parameters for the first time. This will create new insights on rock weathering and associated rockfall, which are required to understand past and future Alpine landscape evolution and to anticipate future weathering and rockfall trajectories to mitigate Alpine hazards.

• DFG Programme: Research Grants
• International Connection: Netherlands