Glacier and permafrost hazards in cold mountain regions encompass various flood and mass movement processes that are strongly affected by rapid and cumulative climate-induced changes in the alpine cryosphere. 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 large magnitude process chains that can 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. Comprehensive assessments of glacier and permafrost hazards define two core components (or outcomes): 1. Susceptibility and stability assessment: Identifies likelihood and origin of an event based on analyses of wide-ranging triggering and conditioning factors driven by interlinking atmospheric, cryospheric, geological, geomorphological, and hydrological processes. 2. Hazard mapping: Identifies the potential impact on downslope and downstream areas through a combination of process modeling and field mapping that provides 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, Alaska, and the Swiss Alps. At that time, related hazard assessments were reactionary and event-focused, aiming to understand the causes of the disasters and to reduce ongoing threats to communities. These disasters and others that followed, such as Kolka Karmadon in 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. The widespread availability of satellite imagery enables a preemptive approach to hazard assessment, beginning with regional scale first-order susceptibility and 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 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 that consider, for example, the threat from new lakes that are projected to emerge in a 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 a worst-case scenario in a comprehensive, forward-looking, multiscenario hazard assessment.
Assessment Principles for Glacier and Permafrost Hazards in Mountain Regions
Simon Allen, Holger Frey, Wilfried Haeberli, Christian Huggel, Marta Chiarle, and Marten Geertsema
Permafrost-Related Geohazards in Cold Russian Regions
Permafrost, or perennially frozen ground, and the processes linked to the water phase change in ground-pore media are sources of specific dangers to infrastructure and economic activity in cold mountainous regions. Additionally, conventional natural hazards (such as earthquakes, floods, and landslides) assume special characteristics in permafrost territories. Permafrost hazards are created under two conditions. The first is a location with ice-bounded or water-saturated ground, in which the large amount of ice leads to potentially intensive processes of surface settlement or frost heaving. The second is linked with external, natural, and human-made disturbances that change the heat-exchange conditions. The places where ice-bounded ground meets areas that are subject to effective disturbances are the focus of hazard mapping and risk evaluation. The fundamentals of geohazard evaluation and geohazard mapping in permafrost regions were originally developed by Gunnar Beskow, Vladimir Kudryavtsev, Troy Péwé, Oscar Ferrians, Jerry Brown, and other American, European, and Soviet authors from 1940s to the 1980s. Modern knowledge of permafrost hazards was significantly enriched by the publication of Russian book called Permafrost Hazards, part of the six-volume series Natural Hazards in Russia (2000). The book describes, analyses, and evaluates permafrost-related hazards and includes methods for their modeling and mapping. Simultaneous work on permafrost hazard evaluation continued in different countries with the active support of the International Permafrost Association. Prominent contributions during the new period of investigation were published by Drozdov, Clarke, Kääb, Pavlov, Koff and several other thematic groups of researchers. The importance of common international works became evident. The international project RiskNat: A Cross-Border European Project Taking into Account Permafrost-Related Hazards was developed as a new phenomenon in scientific development. The intensive economic development in China presented new challenges for linear transportation routes and hydrologic infrastructures. A study of active fault lines and geological hazards along the Golmud–Lhasa Railway across the Tibetan plateau is a good example of the achievements by Chinese scientists. The method for evaluating the permafrost hazards was based on survey data, monitoring data, and modeling results. The survey data reflected the current environmental conditions, and they are usually shown on a permafrost map. The monitoring data are helpful in understanding the current tendencies of permafrost evolution in different landscapes and regions. The modeling data provided a permafrost forecast that takes climate change and its impact on humans into account. The International Conference on Permafrost in 2016, in Potsdam, Germany, demonstrated the new horizons of conventional and special permafrost mapping in offshore and continental areas. Permafrost hazards concern large and diverse aspects of human life. It is necessary to expand the approach to this problem from geology to also include geography, biology, social sciences, engineering, and other spheres of competencies in order to synthesize local and regional information. The relevance of this branch of science grows with taking into account climate change and the growing number of natural disasters.
Permafrost-Related Geohazards and Infrastructure Construction in Mountainous Environments
Lukas U. Arenson and Matthias Jakob
Mountain environments, home to about 12% of the global population and covering nearly a quarter of the global land surface, create hazardous conditions for various infrastructures. The economic and ecologic importance of these environments for tourism, transportation, hydropower generation, or natural resource extraction requires that direct and indirect interactions between infrastructures and geohazards be evaluated. Construction of infrastructure in mountain permafrost environments can change the ground thermal regime, affect gravity-driven processes, impact the strength of ice-rich foundations, or result in permafrost aggradation via natural convection. The severity of impact, and whether permafrost will degrade or aggrade in response to the construction, is a function of numerous parameters including climate change, which needs to be considered when evaluating the changes in existing or formation of new geohazards. The main challenge relates to the uncertainties associated with the projections of medium- (decadal) and long-term (century-scale) climate change. A fundamental understanding of the various processes at play and a good knowledge of the foundation conditions is required to ascertain that infrastructure in permafrost environment functions as intended. Many of the tools required for identifying geohazards in the periglacial and appropriate risk management strategies are already available.