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
Debris-Flow Risk Assessment
Matthias Jakob, Kris Holm, and Scott McDougall
Debris flows are one of the most destructive landslide processes worldwide, given their ubiquity in mountainous areas occupied by human settlement or industrial facilities around the world. Given the episodic nature of debris flows, these hazards are often un- or under-recognized. Three fundamental components of debris-flow risk assessments include frequency-magnitude analysis, numerical scenario modeling, and consequence analysis to estimate the severity of damage and loss. Recent advances in frequency-magnitude analysis take advantage of developments in methods to estimate the age of deposits and size of past and potential future events. Notwithstanding, creating reliable frequency-magnitude relationships is often challenged by practical limitations to investigate and statistically analyze past debris-flow events that are often discontinuous, as well as temporally and spatially censored. To estimate flow runout and destructive potential, several models are used worldwide. Simple empirical models have been developed based on statistical geometric correlations, and two-dimensional and three-dimensional numerical models are commercially available. Quantitative risk assessment (QRA) methods for assessing public safety were developed for the nuclear industry in the 1970s and have been applied to landslide risk in Hong Kong starting in 1998. Debris-flow risk analyses estimate the likelihood of a variety of consequences. Quantitative approaches involve prediction of the annual probability of loss of life to individuals or groups and estimates of annualized economic losses. Recent progress in quantitative debris-flow risk analyses include improved methods to characterize elements at risk within a GIS environment and estimates of their vulnerability to impact. Improvements have also been made in how these risks are communicated to decision makers and stakeholders, including graphic display on conventional and interactive online maps. Substantial limitations remain, including the practical impossibility of estimating every direct and indirect risk associated with debris flows and a shortage of data to estimate vulnerabilities to debris-flow impact. Despite these limitations, quantitative debris-flow risk assessment is becoming a preferred framework for decision makers in some jurisdictions, to compare risks to defined risk tolerance thresholds, support decisions to reduce risk, and quantify the residual risk remaining following implementation of risk reduction measures.
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.
Risk Governance of Limited-Notice or No-Notice Natural Hazards
Maria Papathoma-Köhle and Dale Dominey-Howes
The second priority of the Sendai Framework for Disaster Risk Reduction 2015–2030 stresses that, to efficiently manage risk posed by natural hazards, disaster risk governance should be strengthened for all phases of the disaster cycle. Disaster management should be based on adequate strategies and plans, guidance, and inter-sector coordination and communication, as well as the participation and inclusion of all relevant stakeholders—including the general public. Natural hazards that occur with limited-notice or no-notice (LNN) challenge these efforts. Different types of natural hazards present different challenges to societies in the Global North and the Global South in terms of detection, monitoring, and early warning (and then response and recovery). For example, some natural hazards occur suddenly with little or no warning (e.g., earthquakes, landslides, tsunamis, snow avalanches, flash floods, etc.) whereas others are slow onset (e.g., drought and desertification). Natural hazards such as hurricanes, volcanic eruptions, and floods may unfold at a pace that affords decision-makers and emergency managers enough time to affect warnings and to undertake preparedness and mitigative activities. Others do not. Detection and monitoring technologies (e.g., seismometers, stream gauges, meteorological forecasting equipment) and early warning systems (e.g., The Australian Tsunami Warning System) have been developed for a number of natural hazard types. However, their reliability and effectiveness vary with the phenomenon and its location. For example, tsunamis generated by submarine landslides occur without notice, generally rendering tsunami-warning systems inadequate. Where warnings are unreliable or mis-timed, there are serious implications for risk governance processes and practices. To assist in the management of LNN events, we suggest emphasis should be given to the preparedness and mitigation phases of the disaster cycle, and in particular, to efforts to engage and educate the public. Risk and vulnerability assessment is also of paramount importance. The identification of especially vulnerable groups, appropriate land use planning, and the introduction and enforcement of building codes and reinforcement regulations, can all help to reduce casualties and damage to the built environment caused by unexpected events. Moreover, emergency plans have to adapt accordingly as they may differ from the evacuation plans for events with a longer lead-time. Risk transfer mechanisms, such as insurance, and public-private partnerships should be strengthened, and redevelopment should consider relocation and reinforcement of new buildings. Finally, participation by relevant stakeholders is a key concept for the management of LNN events as it is also a central component for efficient risk governance. All relevant stakeholders should be identified and included in decisions and their implementation, supported by good communication before, during, and after natural hazard events. The implications for risk governance of a number of natural hazards are presented and illustrated with examples from different countries from the Global North and the Global South.