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A Global Assessment of Glacier Outburst Floods
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A Global Assessment of Glacier Outburst Floods
Executive Summary and Introduction
Floods on the glacier are massive quantities of water suddenly released from a glacier. A glacier lake flares out, regardless of subtype, reason or technique, is a sudden discharge of water or part of it retained in a glacial lake (GLOF) (Wikstrom Jones & Wolken, 2019). They are a common natural hazard found worldwide. They are linked mainly to climate through glacial mass balance and have a partly demographic and land use impact for society. With continued climate change, land use and population dispersal, it is crucial to recognize the spatial pattern and effects of glacier outbursts. This study includes data from six continents and a century-old glacier flood. The floods of glaciers in Iceland, South America 5745, European Alpine Europe 393 and Central Asia 6300 have killed at least seven people (Ramskogler et al., 2020). There having been less flooding but more damage to Nepal, Peru and India. Floods flooded agricultural land, destroyed households, damaged roads, and affected infrastructure, with 10 percent of the glacier sites in South America producing people murdered and affected infrastructures and with 15 percent of Central Asian site flooding, destroying homes, damaged roads and deteriorated infrastructures flooding agricultural land (Chen & Cho, 2019).
The repercussions of glacier floods on Bhutan and Nepal are most national. In order to better understand spatiotemporal patterns in glacier flood events and size, we suggest reliable, complete and harmonized glacier flood control, recording and reporting. Future global glacial flood modelling has to take account of land-use changes as well as the likely distribution of geomorphological reactions to climate change and human activities.

Background
Jökulhlaups are unexpected discharges of significant amounts of water from a glacier, and are also known as glacial outbursts. The hydrographic qualities of these floods are comparable to dam break flooding, as they usually result from the breaking down of glacial lakes, ice, moraine or sloping dams (Lindbäck, 2019). They include subglacial volcanic or geothermal floods and strong precipitation that fall extraordinarily swiftly through glacier catchments. The outbursts of a glacier and hydrographs occur through the downwashing of a glacier and subsequent discharge of meltwater. Environmental factors that in turn have an impact on climate conditions control the creation and development of ice- and morain-dammed Lakes (Peyaud et al., 2007). Climate can affect the characteristics of certain glacier outbreaks like onset and peak releases.
The number and area of the glacial lakes worldwide is increasing as a result of continuous global deglaciation. Volcanic activity under ice weights, through virtual ice melts and by drainage of meltwasser momentarily held in a water bag or glacier lake, can lead to glacial flooding.Glacier outbursts have been witnessed for millennia especially in Iceland and Europe, where records date from the 1500s (Carrivick & Tweed, 2019). Glacier floods have a social effect, including the immediate destruction and damage to infrastructure and property, community instability and loss of life, as demonstrated in the Alps of Europe, South America, and the Himalayas. As a consequence of a glacier outburst of Lac du Mauvoisin that was recognized to influence scientific thinking about glacial and geological geology, hundreds of people have perished and houses and infrastructure has been destroyed, thus launching modern science.
Lyell (1830) effectively opposed catastrophic events in his work on ‘Geology Principles’ and paved the path for scientical thought which acknowledged ice ages in the past, and therefore a changing climate (Costa, 2013). Secondly: Ignaz Venetz was a Swiss engineer responsible with water drainage from the Lac du Mauvoisin and conducted the first Alpine glacier investigation (Hellmann et al., 2020). He and John de Charpentier, Jens Esmark, William Buckland, and lastly Louis Agassiz examined the link between glacial fluctuation and ecological change. Recent major research has examined the conceptualisation of sources, triggers and processes, physical mechanics that drive the production and routing of the meltwater through the glacier and the landscape consequences. While in these and other regional research reports the repercussions of glacier spring fluxes are often stressed, a thorough worldwide impact assessment of glacier spring flooding has yet to be conducted on communities.
The aim of this study is to offer a global assessment of the implications of glacier floods. We concentrate mostly on descriptive statistics of and relative importance of glacial floods because it is demonstrated, given the nature of current data, it is difficult to determine the absolute impact of most occurrences. In order to be clear, throughout this text ‘glacier floods’ are called ‘glacier floods.’ Glacial floods are referred to as “floods” for the sake of this work.
Mechanisms and Causes of Glacial Lake Outburst Floods (GLOF)
There are a number of sources and procedures utilized to discharge water for flooding induced by glacial lake outburst. Causes are linked with mechanisms and not every possible combination is viable. In addition, various subtypes of the glacial lake are susceptible to various causes and processes of flooding. Many studies have been carried out to study the cause of the lake explosions in particular lake subtypes and regions but to better understand the complex processes and, therefore, to ensure more efficient risk and hazard management, systemic research into the causes and the mechanisms of the Glacial Lake Outburst flow, as well as the database development, are essential.

Movement of the Slope into the Lake at a Rapid Pace
The lake can generate a lake explosion when quick slides such as toboggans, falls, avalanches and flows contact the lake. Like moraine and ice dams, quick movement in the lake leads to displacement waves that can rapidly cause the dam to overtop or break. The main source of Glacial Lake Outburst Flood in the Himalayas and Andes has been identified as several forms of rapid downhill movement, including ice avalanche.
According to the Lake Outburst Floods in the Cordillera Blanca in Peru, despite tens of meters of dam freeboard, displacement waves can overwhelm the dam under such circumstances (Vilca et al., 2021). There have been many accounts from throughout the world of Glacial Lake Outburst Floods produced by fast slope changes. Slope movements in high mountain locations are considered to have increased as a result of climate change. These slope motions are associated with ice avalanches, glacier ice loss, and rock/ice avalanches, as well as a variety of other slope motions associated with permafrost degradation.

Snow Melt/ Heavy Rainfall
Improved dumping High rainfall, heavy snowmelt or a combination of the two leads to increased water inflow from a lake. Greater discharge in moraine-dammed lakes, and also maybe in ice-dammed lakes, may result in a greater amount of erosion and outflow incision into the dam. Many Glacial Lake Outburst Flooding in British Columbia and the US Cascade Range, notably the 1920s Tide Lake Outburst Flood and the lake beneath Dellier Glacier, were responsible for heavy rains. The 2013 Glacial Lake Outburst Floods on Chorabari Lake in the India Garhwal Himalayas, which culminated in the Kedarnath calamity, also contributed to heavy rain (Kc et al., 2021). Heavy rain can operate as an indirect cause of the outburst of Glacial Lake when it generates pathways into the lake.
Flooding from an Upstream Lake
Glacial lakes are usually structured into cascade patterns inside certain valleys. Outburst Glacial Lake Floods can occur when glacial floods are blowing from upstream lakes downstream. During the downstream lakes, the intensity and size of a downstream flood can either be increased by discharging stored water or by lowering the volume of the flood by maintaining water the intensity and size of the water. Increasingly, scientists concentrated on these complicated connections with chain processes that will likely take hold in the future.
Melting of Ice in the Dam/Formation of the Dam
In ice-dammed lakes, maybe moraine-dammed lakes if a dam has a “icelen” or “dead” lens and lakes, dammed in an environment of dry permafrost, such as lakes, dammed by rock glaciers, ice is melted in dams. Throughout the creation of the lagoon and occurrence of explosive flux caused by slope motions induced by permafrost, permafrost thawing and degradation might thus play a significant role. Drainage of a tunnel into the Basal Ice, marginal ice drainage with part of the ice dam physically collapses or a combination of both is induced by flooding from ice dam lakes.
The volcanic Jökulhlaup volcanic explosion flood caused by the lake is a form of volcanic explosion. The fusion of ice cores in an ice-cored moraine lake can cause the dam and tubes to collapse in structure as well as a dam subsidy which can lead to additional surface outflow(s), incisions and breaches.
Subsurface Outflow Tunnels Being Obstructed
Glacial lakes that are not available in moraine or ice dams are sensitive to river-borne debris and fluxes, such as slopes on the internal slopes of the moraine dams that enclose outflow tunnels. The dam’s internal structure is affected by an earthquake; the outflow channels of the dam are freezing. When the subsurface outflow tunnel(s) are closed, the lake level would rise and the dam can break down due to increased hydrostatic pressure or the dam incision. On July 11, 1981, the moraine dam at Lake Zhangzhanbo in Tibet failed due to the blockage of underground outflow pipes (Rivas et al., 2015).
Dam Degradation Over Time
Spontaneous moraine (icy) dam failure without a dynamic cause, can be explained by long-term degrading mechanisms such as dam-self destruction, such as slow changes in the internal structure of the dam leading to piping and collapse or hydrostatic pressure. This source was accused for the many floods in the Hindu Kush Himalayas, especially those in Lake Lugge Tsho, Bhutan Himalaya in Glacial Lake Outburst in 1994, resulting in the depths of the lake due to increased hydrostatic pressure produced by the basal ice melting.

Recent Glacier Retreat, Climate Oscillations, and the Glaciation Cycle
The Quaternary Period
The Quaternary epoch, which lasted 2.588 million years and included ice ages, glacial periods, and interglacial occurrences, was characterized by many climatic variations. Colder glacial periods, in general, have a larger glacierized area, whereas interglacial events have a lesser ice extent (Kasse, 2012). According to marine isotope oxygen phase, about a hundred changes occurred over the quaternary period of warmer and warmer paleoclimates (MIS). The Holocene period is distinguished by variable climate conditions in space and time, as well as glacial reactions.
Little Ice Age (LIA) Glacier Retreat and Post-LIA Glacier Retreat
The Little Ice Age (LIA) was the Holocene’s final colder epoch, lasting from 1400-1700 AD, with the biggest cooling in the northern hemisphere. In the majority of high-altitude mountainous and high-latitude Arctic areas, post-LIA climatic change, globe ice loss and glacier retreat have been documented. Between 1850 and 1970, the Alpine Glaciers lost 35%, but between 1850 and 2000 they lost around 50% (Leigh et al., 2020). Alpine glaciers lost an estimated two-thirds of their ice during this period. Numerous studies have been conducted, for example, in the Alps, Andes, and Himalayas, to estimate recent glacier changes in a regional context.
Glacial Lake Formation and Evolution
The emergence and growth of several subtypes of glacial lakes are frequently followed by the loss and retreat of glacial ice. Some of them are ice-stick lakes, moraine-sticking lakes and lakes that are rock-sticking. In reaction to glacial retreat, Moraine- and Rock-broken lakes develop from proglacial stages of immediate touch with the mother tongue to glacier-detached phases of non-direct contact with certain glaciers in the catchment to nonglacial phases of no glaciers in the collection.Generally specified stages are linked to the threat of a particular lake, such as floods from the lake. Most Glacial Lake Outburst Floods (70%) have been observed due to ice blocked lakes (Wikstrom Jones & Wolken, 2019). Flooding out of lakes is regarded to be a separate pattern of evolution that may never occur once, however different subtypes of glacial lakes are subject to various causes and subsequent lake explosion processes.
Lakes That Have Been Flooded by Ice
Ice dam lakes can be situated on top of supraglacial lakes in the glaciers, under sub-glacial lakes in the glaciers, or on the glacier borders. The creation of ice dams was related to climatic changes, the loss of glacier ice and surge activities of glaciers. Surge glaciers sometimes experience large flow accelerations, usually alongside terminal advances, leading to valleys being blocked and the lake formed: that is, a main valley was blocked by the rising glacier in a valley on the sides, or a side valles blocked by an uplifting glacier in the main valley. The creation of ice dams and ensuing flares was witnessed on multiple occasions.
Ice dammed lakes range from little pools up to 10 meters in capacity to enormously wide lakes with capacity of more than 10 meters. Large ice dammed lakes, especially in high latitude locales, exist in plain topography settings. The development of small supra-Lakes and its eventual merger frequently precede the establishment in the correct topographical circumstances of a moraine or ground-blocked glacial lake. On one hand, ice dams are often transitory, and when a portion of the imprisoned waters is released, ice cream-strung lakes are likely to blow up. The ice-dammed lakes are prone to overtopping and dam collapse processes for both water discharge dams. On the other hand, large ice dam lakes can endure for millennia if the weather is stable.
Lakes that have been dammed by the moraine
Moraine-dammed lakes are lakes held by every kind of moraine. Morain-dammed lakes, depending on the damming moraine, can form in various situations. Lakes with moraine dams are typically found in mountainous places and can be up to 10 meters in volume (Frey, 2021). During early periods of glacial retreat, moraines-dammed lakes such as the LIA-Moraine-dammed lakes which developed during the Little Ice Ages, were discovered to have receded from their maximum places with moraines.
Moraine-blocked lakes can also occur during buried dead ice cream, as can be shown in the creation and extension of Lake Imja in the 1980-90s (Pryakhina et al., 2021). Dam overtops and dam collapses are common in moraine dammed lakes and most Glacial Lake outbursts happen when lakes are exposed to baling processes and wave displacements. early stage of lake growth is a forecast of the lake development.

Lakes That Have Been Flooded by Bedrock
In glacial depressions, glacial lakes buried in basement can be found. Rock dams are considered stable rock structures. The dam overtopping hence is the only mechanism for the explosion of a lake in this subtype of the glacial lake. The formation of lakes dammed by moraine prevails in the early phases of glacier retreat, i.e. LIA moraines, but in the later phases, i.e. LIA circuses and bedrocks, the production of bedrock lakes predominate in the postLIA glacier retreat patterns seen. Such rock dammed lakes as moraine dammed lakes, especially susceptible to outbursts, if they undergo calving activities in the early proglacial period.
Perspectives for the future
In the majority of mountains worldwide, the post-LIA glacier loss and retreat has been seen, and this trend is predicted to continue or accelerate in the 21st century. For increased management, over-depths of glacer beds are anticipated to identify places for new possibly dangerous lakes in future. In order to improve the risk management of Glacial Lake Outburst Floods. Current lakes are more and more fragile as glaciers continue to decline from outbursts resulting from the ice avalanche/calving process.
The amount of water in it may dramatically fluctuate in the course of time. The glacial lakes, when exposed to calving processes and ice avalanches, are more susceptible to an outburst at the end of their proglacial phase when the volume of lake is high, whereas in the glaciar-detached phase (phase II) the outburst flood is less likely when the vulnerability is reduced in the atmosphere and residual susceptibility exists only (Phase III).
Data Sources, Methods and Analysis
Data Sources
An Open-Office spreadsheet with seven sheets titled after the regions for which we obtained historical Glacial Lake Outburst Floods occurrences was accessible as of July 31, 2021. Each sheet has 32 columns with the attributes for each Glacial Lake Outburst Floods that we were able to get. Empty cells indicate ‘No Data.’ The name of the column is displayed first, followed by two rows of extra text and data structure information. The data in the columns ‘Major RGI Region,’ ‘Mountain range Region,’ ‘Glacier,’ ‘RGI Glacier Id,’ and ‘RGI Glacier Area’ are taken from the Randolph Glacier Inventory, Version 6.0 (GLIMS: Global Land Ice Measurements from Space, n.d.).

Methods and Analysis
The first step in analyzing Glacial Lake Outburst Floods is to properly identify hazardous lakes or lakes prone to lake outburst floods. Unlike “classical” hydrometeorologically induced floods, Glacial Lake Outburst Floods are rare and cannot generally be anticipated using return periods; moreover, the threat changes with time, signifying the development of a specific lake (Dahlquist & West, 2021). A variety of primarily remotely sensed data-based methods for detecting dangerous lakes have been developed for diverse settings.
Regionally based approaches appear to be the most realistic solution, reflecting the several primary causes of Glacial Lake Outburst Floods in different situations. Some examples include methods created for the Himalaya area, Blanca, British Columbia, Peru, and the Swiss Alps (Villa, 2020). The majority of methods are based on the evaluation of selected features which indicate an increase in the likelihood of lake explant floods dividing into three categories: dam features like dam type, dam freeboard and dam geometry; lake features like lake area and volume; and lake surrounding features such as the glacier and the path.
Detailing potential areas and identifying subsequent elements at risk usually is based on a number of modeling approaches such as digital elevation models and pre-defined event-triggering scenarios, including the incline movement of a particular volume into the lake and validation of previous Glacial Lake Outburst Floods (Allen et al., 2021). Once hazardous lakes have been identified and potentially impacted regions have been identified, the elements at risk are shown.
Naturally, these techniques are laden with uncertainty and possible drawbacks; nonetheless, they have shown to be useful in risk management for Glacial Lake Outburst Floods. As a result, risk reduction strategy and vulnerability reduction are often employed to lower the risk of Outburst Floods on Glacial Lake.
We showed the total number of outbursts per area by study and dam type of glacial lake, to give a feeling of the frequency of outburst flows from Glacial Lake in the research regions:

We also created a stacked bar plot with the overall number of Glacial Lake Outburst Floods by decade, research region, and dam type:

Conclusion
The loss and retreat of ice from glaciers has been a subject of intensive investigation in many regions worldwide, typically in combination with the birth and evolution of lakes, glacier lakes, icedamed lakes and moraine lakes and rock-damped lakes. In locations which have become deglaciated during the Little Ice Age when the last significant glacier progress has been occurring, a big number of glacial lakes have formed. These lakes are usually dynamic, short-lived entities. Glacial Lake Outburst Floods are a sort of glacial lake evolutionary pattern in which a portion of the lake’s held water is abruptly released, independent of the reason, process, or glacial lake subtype involved.
Rapid pitching in the lagoon; high rainfall/snow melt; upstream lake cascade flooding; terrible ice melting; jökulhlaups caused ice melting / molding of the dam including volcanic activity; sub-surface exit tunnels can be blocked with suction only; the retreat of the glacer is linked with most causes, either directly or indirectly. There may be two different mechanisms for water release following causal processes: lake-outburst flood dams which are overturned by a wave of displacement, with the bulk of the water released flows on the dam without causing damage; and dam failures where most of the released water is released by dam failure, including direct dam rupture, tube, incision and infringement and inoculation. Certain causes and glacial lake subtypes are connected, and even little triggering events may lead to huge and devastating processes.
The hydrological significance of Glacial Lake Outburst Floods exceeds peak discharges considerably from the hydrometeorological floods resulting in an unparalleled erosion and transport potential. Therefore, when erodable material is present, it usually becomes flow-type movement, as does the flow of garbage. The main Outburst Lake Glacial floods documented have brought about significant modification in geomorphology. The Glacial Lake Outburst Floods may have disastrous social impacts if populated areas are affected by this. In Andes and the Hinduc Kush Himalayas, fatal glacial lake Outburst Floods have been seen.
As a result, the production and development of several new, potentially dangerous glacial lakes as a result of continuing climate change, the dangers of Glacial Lake Outburst Floods are expected to increase, typically together to increase vulnerability of the components at risk and to increase their adaptive capacity.

References
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