CONSTRAINING THE ROLE OF WEATHER CONDITIONS IN DRIVING DAMAGE ACCUMULATION LEADING TO ROCKFALL

Rockfalls constitute a persistent geohazard in steep topographies and are key agents of landscape erosion in upland, coastal and cut-slope environments. Long-term climate and short-term weather conditions, notably rainfall and temperature, are cited as fundamental controls on rockfall initiation. The intricacies of how weather and climate drive rock-mass damage accumulation, and failure (manifested as rockfalls), are poorly constrained. This partially stems from limited availability of monitoring data at an appropriate resolution that captures variations in environmental conditions that drive progressive failure of rock-masses. Average weather conditions are anticipated to change at both global and local scales under projected climate change. Thus, understanding the interplay between weather, damage accumulation and rock-slope failure is crucial in constraining how future rockfall hazard will evolve.

To address this, we monitored rock-slope deformation and rockfall activity over a 1-year period using ±0.05 m resolution hourly terrestrial-laser-scanning (TLS) and thermal imaging along an actively failing coastal rockface in the UK. This rock-face has previously shown deformation indicative of progressive failure mechanisms. We supplemented cliff-face monitoring with cliff-top sandstone slabs (pseudo-rock-faces), monitored for microcrack-generated acoustic emissions. Monitoring of cliff-top weather conditions provided a minute-by-minute resolution catalogue of localised conditions. In combination, these field-monitoring approaches have provided insight into diurnal, seasonal and episodic rock-damage accumulation (microcracking) driven by weather conditions, with simultaneous monitoring of corresponding cliff-face rockfall activity (TLS). We present initial results of our monitoring programme and provide a physically-based conceptual model to explain how weather conditions ultimately drive rockfall activity and, in turn, how rockfall hazard may respond to projected climate change.