Glacial Hazards References Revision

Srestha et al., 2023

• As glaciers recede and surrounding slopes become increasingly unstable, GLOF events are expected to increase; between 1833 and 2022 there were 697 individual GLOFs documented in High Mountain Asia with nearly 7000 fatalities

• High Mountain Asia has the largest expanse of glacial ice between the two poles and has around 30,000 glacial lakes but these have been retreating and losing mass since the 1960s leading to the formation and rapid expansion of glacial lakes, a trend expected to create new hotspots of hazardous lakes with implications for GLOF hazards and risk

• Processes identified as direct or indirect triggers include slope movements such as rockfalls, avalanches or landslides into lakes to form overtipping waves as well as intense rainfall or ice melt leading to an increase in water levels that strain dams; these then cause fatalities as well as damaging infrastructure and farmlands as developments grown in downstream areas to increase risk

• There is a peak in GLOFs seasonally where westerlies bring South Asian monsoons to show that regional precipitation is an important driver of outburst flooding in the region

• The hazard of a GLOF is closely associated with moraine stability which is linked to the history of glacier retreat with areas of recent permafrost change likely to be more susceptible to mass movement

• Distributed datasets on infrastructure, population and ecosystems would allow for assessments on impacts and vulnerabilities when coupled with potential paths and remotely sensed vegetation data; this would allow for estimates of local economic and ecological impacts to form hazard zonation maps

Miner et al., 2020

• In the Mount Everest Region risks arise from a natural and anthropogenic changes to the biological system leading to diverse risks to ecosystems, human health, geology and climbing conditions; as high mountain glaciers worldwide decrease in extent and volume there are significant consequences to water availability, hazards such as outburst floods and slope failure, ecosystems and socioeconomic futures

• There are risks of seismic hazards, landslides and avalanches as well as rockslides that become more frequent as glaciers melt away from headwalls and expose steep unstable rock faces

• Rain events can trigger flooding, often this water can be contaminated by chemicals, pesticides and anthropogenic metals meaning that drinking water sourced from snow and ice melt poses a risk to human health; climbers can also lead pathogenic organisms in meltwater

• These risks are diverse and constantly changing so much be monitored in order to inform proper adaptation and mitigation of risks to tourism and local populations

Worni et al., 2014

• Many recent GLOF events involve process chains where mass movement impacts glacial lakes to trigger dambreaches and cause outburst floods; the effects of climate change and increased instability of high mountain slopes pose a threat as they may exacerbate process chains 

• GLOF events compromise a series of cascading processes that should be modelled to improve our understanding and assessment of future hazards as new glacial lakes form and slopes destabilise

• The initiation of process chains can differ e.g. rock fall, precipitation, upstream GLOF but they typically begin with an impulse-wave generation, dam overtopping and breaching and then lake emptying and flood propagation

• The stability of dams depends on their geometry, internal structure, material properties and particle size/distribution; once they are overtopped they initiate dam erosion that continually increases hydraulic forces to enlarge the breach in an irreversible process leading to the emptying of the lake

Sherpa et al., 2019

• GLOFs are among the most serious cryospheric hazards for mountain communities and people’s perceptions of cryospheric risks can influence their actions, beliefs and responses to hazards; there has been a positive correlation found between perceptions of risk and livelihood sources of tourism and spatial proximity to glacial lakes

• There is much uncertainty and confusion related to GLOF risks often stemming from a disconnect in how scientific information is communicated to local communities, how policies are formed and awareness campaigns; there is a need to form a sustainable partnership of scientists, policymakers and local communities to improve cryospheric risk management 

• Only in recent years have social and humanistic perspectives on GLOFs emerged, but there is a need for an interdisciplinary approach to capturing the natural-social interactions of cryospheric hazards and appreciating that people's risk perceptions are shaped by direct personal experiences and second hand information, this perception influence how a person may act in the event of a hazard

• Rapid onset hazards have a perceived higher risk; local perception was also influenced by source of livelihood, age, prior experience and geography with younger people more likely to perceive a risk alongside those who support their livelihoods with tourism, those with prior experience of the hazard and living closer to lakes

Bajracharya et al., 2007

• Information on the extent and possible impact of GLOFs can be used for designing early warning systems and implementing management plans for lakes such as Imja Lake which is the largest and most dangerous in the Sagarmatha region

• Flooding occurs due to the breaking down of moraine dams leading to flash floods and debris flow downstream, pressures are increasing due to increased populations and tourism in mountain areas causing people to settle in areas highly exposed to natural hazards and trekking routes often leading through unsafe areas in floodways

• The most vulnerable areas were identified as settlements with agricultural land along river banks with scattered housing in vulnerable zones; around 5.8km of trails were judged as highly vulnerable due to running through flood plains

• Vulnerability maps generated through hydrodynamic modelling provide a systematic basis for identifying vulnerable populations, infrastructure and agricultural land and this can be used to develop management plans

Emmer, 2017

• Glacier retreat is connected to interrelated geomorphological processes and changes in hydrological regimes

• GLOFs are characterised by extreme peak discharges, exceptional erosion and transport potential and pose risks to human society potentially driven by anthropogenic climate change

• Despite regional differences in triggers and mechanisms, GLOFs are closely tied to the formation and evolution of new lakes and triggers

Salerno et al., 2017

• From the 1950s to 1990s there has been an overall decrease in glacier area as a result of temperature and precipitation variation, this is important as ice masses in the Himalayas constitute a water resource assuring the survival of around 500 million people in the area 

• The glaciers of the Sagarmatha national park are nearly all debris-covered, a characteristic that alters exchanges between ice and the atmosphere with the debris cover gradually increasing towards the lower part of the glacier ablation zone

Cenderelli & Wohl, 2001

• GLOFS can dramatically modify channels and valleys in the regions they affect by eroding, transporting and depositing large quantities of sediment for tends of km along flood routes

• GLOF discharges in the Mount Everest region were 7-60x greater than seasonal high flow flood discharges, with the greatest discharge occurring nearest to the moraines and declining downstream

Benn et al., 2012

• Superglacial debris cover can alter rates and spatial patterns of melting, this can be associated with the formation of moraine-dammed lakes that pose a risk of GLOFs as downwasting allows for supraglacial lake hollows to extend

• The probability of a flood is a function of lake volume, the geometry and structure of the dam and possible trigger mechanisms; these events can then lead to a loss of life, dwellings, infrastructure and farmland

• A major factor in determining GLOF potential is the hydraulic gradient across the moraine dam influencing its susceptibility to seepage as well as trigger mechanisms that can cause waves to overtop and erode moraine dams to initiate positive feedback loops of discharge and erosion

• At risk sites there is a need to continue to monitor the complex webs of factors that contribute to the occurrence of GLOF hazards through in situ and remote sensing techniques, predictions of GLOF impact should be based on a scientific basis and have clear criteria for prioritising mitigation efforts

Hambrey et al., 2008

• Many Himalayan glaciers are enclosed by Little Ice Age moraine complexes which impound lakes, these dams can attain heights of over 100 metres and are made up of poorly sorted mixtures of sand and gravel; behind the dams there are lakes several kilometers long 

• During a GLOF, discharges of up to 60x greater than normal flow have been reported with a particularly high impact in the upper 16km of flood routes and with further consequences up to 200km downstream

• At debris covered glaciers downwasting (or vertical thinning) combined with a progressive reduction in slope profile sees supraglacial debris thicken towards the snout, forming and adding to terminal moraine dams behind which lakes are fed by glacial melt and precipitation, and expand due to cliff calving

Zheng et al., 2024

• A GLOF occurred in June 2020 in Tibet with a peak discharge of 5602 cubic meters per second, the landslide triggering the GLOF was likely caused by heavy south Asian monsoon rainfall in the same month that led to dam overtopping and erosion

• There were no casualties but there was severe destruction to villages and infrastructure downstream mainly to buildings, roads, bridges and farmland; there was great erosion of the river valley and alteration of the channel

• As the event took place in the daytime, villagers were upstream collecting herbs and were able to observe the flood and inform downstream populations to evacuate, leading to no casualties in this event

Cuffey & Paterson, 2010

• A jokulhlaup is the sudden and rapid drainage of a glacier-dammed lake that can cause extensive flooding and pose a great hazard to populations downstream

• They can occur once per year or only every several years, the flood can start when the level gets very high and may stop before the lake has emptied

• These floods often occur due to melt and transport sediment that is deposited in broad outwash plains at the periphery of ice caps

Motschmann et al., 2020

• GLOFs and water scarcity are often assessed by separate methods and by separate research communities despite being intertwined and shaped by multi-dimensional natural and socioeconomic drivers

• GLOF threat increases at the same time as declining melt water supply changes in the hydrological regime resulting in changing water availability

• There is a need to form more comprehensive analysis of risks related to water resources by considering climate change within multi-dimensional drivers across different scales and complex climate sensitive mountain regions to include local perspectives on risk reduction, adaptation and water management

Washakh et al., 2019

• In Nepal, there is a further risk posed to river basins housing hydropower plants that are key to generating income, forming reliable power sources and alleviating poverty

• If these power plants are hit by high discharges, they may be damaged or destroyed, leading to socioeconomic decline throughout the region

• In light of these wide ranging risks associated with GLOF events, there is a clear need to provide comprehensive risk assessments of fragile water and energy systems

Kumupulainen, 2006

• Vulnerability refers to the susceptibility of people, communities or regions to natural or technological hazards through three key dimensions of economic, social and ecological vulnerability

• Risk = hazard potential x exposure x vulnerability; vulnerability can be measured in terms of economic damage potential (economies, communication networks, infrastructure, production, distribution, consumption etc.), social coping capacities (the poorest find it harder to reconstruct their lives after a hazard) or ecological (ecosystems response to shocks)

• Vulnerability is broadly defined as the potential for loss but can be understood, measured and mapped in different ways; in the future there is a need to continue to research hazard centred and region centred vulnerability

United Nations Office for Disaster Risk Reduction, 2017

• Hazard is defined as a dangerous phenomenon, substance, human activity or condition that may cause loss of life, injury or other health impacts, property damage, loss of livelihoods and services, social and economic disruption or environmental damage

• Risk = hazard potential x exposure x vulnerability; this combines the probability of an event and its negative consequences to calculate the potential loss of life, injury or destroyed or damaged assets which could occur to a system, society or community in a specific period

Ding et al., 2021

• The cryosphere is very sensitive to global warming, with elevated temperature rise in high latitude and latitude areas it is dramatically changing through ice sheets melting, glaciers retreating, permafrost degrading and snow cover extent decreasing

• The atmospheric cryosphere involves hazards of frost, hail, freeze rain and extreme winter events; the oceanic sea ice, icebergs, coastal erosion and sea level rise; the land glacial hazards, collapse, debris flow as well as heavy snowfall, avalanches, flooding and permafrost hazards that all have effects to human livelihoods, economic assemblages, ecosystems and infrastructure in varied manners

• Although the cryosphere is shrinking as a result of climate change, cryospheric hazards will likely increase in both frequency and severity in a warming climate

Elia et al., 2023

• There has been less attention paid to natural hazards occurring in cryospheric environments than those in mid-latitudes as a result of periglacial regions hosting smaller human populations and therefore understanding and modelling hazards is seen as less prominent of a concern; however, this is changing as global warming radically changes periglacial surface processes and geomorphological processes

• Degrading permafrost has led to regressive thaw slumps and active layer detachments as types of cryospheric slope failure hazards, their development negatively affects human settlements, infrastructure and ecosystems due to changes to sediment budgets and releases of methane and carbon dioxide as permafrost melts 

• As a result, data-driven models were formed in order to improve understanding of cryospheric dynamics, map the susceptibility to certain slope failures and quantify potential impacts 

• The modelling protocol was successfully able to map areas prone to land failure and summarise this into a multi-hazard susceptibility map for Northern Alaska that could be used to mitigate against damage to infrastructure and ecosystems, as well as highlighting the role of unconsolidated materials, temperatures and snow covers in the incidence of these hazards

• Models are limited in their transferability meaning there should be more efforts to map cryospheric multi-hazards in ways that can be helpful in tailoring local adaptation and mitigation strategies

Nicu et al., 2023

• The Svalbard Archipelago represents the northernmost place on Earth where cryospheric hazards including thaw slumps and thermo-erosion gullies could take place and develop due to climatic variations, as permafrost is very sensitive to warming there is a need for a deeper understanding of processes to foresee the dynamics of hazards and future global implications

• Permafrost thawing of internal ice within soils often leads to subsidence and slumps called thermokarst which threats ecosystems, infrastructures and cultural heritage sites alongside releasing GHGs into the atmosphere; in Svalbard thaw slumps and thermo-erosion gullies are of particular interest in the multi-hazard model to understand how they may occur in the same terrain and be mutually triggering 

• Multi-hazard assessment is part of Agenda 21 for Sustainable Development and is highlighted due to the combination of one or more hazards together being more threatening than one, this is especially applicable to cryospheric hazards where little knowledge exists on hazard dynamics

• Data driven models were used to form a multi-hazard susceptibility model of Northern Svalbard to these processes and revealed that different factors drove each, as well as identifying high-risk zones as an important tool for urban planning and risk management 

• This model was the first of its kind in high-Arctic environments and provides an important baseline for further studies of the changing landscape and developing quantifications of future risks to Arctic communities and ecosystems

Clague, 2013

• Glaciers are greatly impacted by climate change with their hazards amplified as a result, most Alpine glaciers reached their largest size near the end of the Little Ice Age but have all thinned and receded in response to warming in the Holocene

• Warming leads to glacier melt and sea level rise with the most catastrophic events predicted with changes to the Greenland and Antarctic Ice Sheets leading to widespread displacement of those living on shorelines and threats to coastal infrastructure

• The thinning and retreat of alpine glaciers have led to rock-slope failures due to declining stability of slopes, this debuttressing can be caused by glacier melt, freeze-thaw weathering and permafrost degradation; rock falls can pose hazards to climbers and tourists at increasing rates in the European Alps and similar areas

• Permafrost thaw and snow cover decline may also lead to an increased frequency of debris flows as a result of slope instability, ice avalanches may also occur as a result of changes to subglacial hydrology; streams may also be impacted due to changes in the delivery of water and sediments from glaciers

• There are theories that large scale deglaciation may be responsible for triggering seismicity or volcanism due to changing stresses on the lithosphere that may induce the upward movement of magma and trigger slipping