Rock Slope Instability in the Proglacial Zone: State of the Art

Abstract

Rock slope failures are characteristic of mountainous environments. These mass movements produce sediment, alter catchment behaviour and contribute to the dynamics and hazards of high alpine and proglacial areas. This chapter highlights the state of knowledge in the context of proglacial environments and reviews methods of investigating rock slope failure activity and causes. An alignment of extreme conditions and dynamic processes renders proglacial environments exceptionally prone to instability. Glacier retreat and climate change, following the Last Glacial Maximum and more recent stadials, has been a major catalyst for past and ongoing mass movements in alpine areas, and many slopes continue to respond to these legacy perturbations. Rock slope failure activity is preconditioned by rock mass properties and topography, and failures in alpine areas are typically prepared or triggered by: (i) fracture growth and seismicity arising from the unloading of glacial loads over millennial timescales, and (ii) rock fracture growth and loss of strength as a result of hydrological and thermal effects that fluctuate over daily to seasonal timescales, but are superimposed upon long-term trends related to climate change. These insights stem from a growing application of geomorphological, geotechnical, geochemical, geodetic and geophysical techniques that enable the assessment of stability factors and the activity of rock slope failures (both past and contemporary). The rich datasets are being used to inform new understanding of past and ongoing proglacial rock slope instabilities; this understanding will ultimately help to predict process dynamics, environmental change and to mitigate hazards resulting from rock slope failures.