Assessment Principles for Glacier and Permafrost Hazards in Mountain Regions

This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Natural Hazard Science. Please check back later for the full article. Glacier and permafrost hazards encompass various flood and mass movement processes that are directly conditioned or triggered by contemporary changes in the alpine cryosphere, threatening lives and livelihoods in most mountain regions of the world. These processes are characterized by a range of spatial and temporal dimensions, from small-volume icefalls and rockfalls that present a frequent but localized danger, to less frequent but larger-magnitude avalanches of ice and/or rock and related process chains that can travel large distances and thereby threaten people and infrastructure located far downstream. Glacial lake outburst floods (GLOFs) have proven particularly devastating, accounting for the most far-reaching disasters in high mountain regions globally. GAPHAZ, the Standing Group on Glacier and Permafrost Hazards of the International Association of Cryospheric Sciences (IACS), and the International Permafrost Association (IPA) recently published a technical guidance document on the assessment of glacier and permafrost hazards in mountain regions, drawing on internationally accepted best practices of integrated hazard assessment, reflecting the scientific state of the art. Here, the main aspects of this guidance document are summarized and reflected in the context of the historic development, current state, and future challenges related to the assessment of glacier- and permafrost-related hazard assessments. In a comprehensive assessment of glacier and permafrost hazards, two core components (or outcomes) are typically included: 1. Susceptibility and stability assessment: Identifying where from, and how likely an event could be, based on analyses of wide-ranging triggering and conditioning factors driven by interlinking atmospheric, cryospheric, geological, geomorphological, and hydrological processes. 2. Hazard mapping: Identifying the potential impact on downslope and downstream areas through a combination of process modeling and field mapping, providing the scientific basis for decision-making and planning. Glacier and permafrost hazards gained prominence around the mid-20th century, especially following a series of major disasters in the Peruvian Andes (Huaraz, 1941, and the Huascarán events of 1962 and 1970), Alaska (Lituya Bay, 1958), and the Swiss Alps (Mattmark, 1965). At the time of these events, related hazard assessments were reactionary and event-focused, aiming to understand the causes of the disasters and assess the ongoing threat to communities. These disasters, and others that followed (e.g., Kolka–Karmadon, 2002), established the fundamental need to consider complex geosystems and cascading processes with their cumulative downstream impacts as one of the distinguishing principles of integrative glacier and permafrost hazard assessment. Nowadays, the widespread and free availability of satellite imagery enables a pre-emptive approach to hazard assessment, beginning with regional-scale first-order susceptibility, hazard assessment, and modeling that provide a first indication of possible unstable slopes or dangerous lakes and related cascading processes. Detailed field investigations and scenario-based hazard mapping can then be appropriately targeted to high-priority areas. In view of the rapidly changing mountain environment, leading beyond historical precedence, there is a clear need for future-oriented scenarios to be integrated into the hazard assessment, considering, for example, the threat from new lakes that are projected to emerge in a continuously deglaciating landscape. In particular, low-probability events with extreme magnitudes are a challenge for authorities to plan for, but such events can be appropriately considered as worst-case scenarios in a comprehensive, forward-looking, multi-scenario hazard assessment.