HIMALAYAN GLACIERS: IMPORTANCE, AVALANCHES AND DANGEROUS FLOODS

HIMALAYAN GLACIERS

20120602-Baltoro_glacier_from air.jpg
Baltoro glacier, one of the largest Himalayan glaciers The vast amount of water stored in Himalayan glaciers plays a crucial role in river flows, hydropower generation and agricultural run in the Ganges, Yangtze, Mekong and Indus river systems in Asia and elsewhere.

A typical Alpine glacier like that found in the Himalayas resembles a hand. The palm is the main part of the glacier and where snow is accumulating and turning into ice. The fingers, sometimes called tongues or snouts, are rivers of ice that flow down various valleys and out of the mountains. Tributary glaciers are similar to the streams that feed a river. They are created in reaches of the mountains, where they scrape off rock and pick up gravel and carry them with into the main glacier, resulting in the twisting, parallel black lines that you often see in large glaciers.

The Nepal-based International Centre for Integrated Mountain Development says, “Small glaciers below 5,000 meters above sea level will probably disappear by the end of the century, whereas larger glaciers well above that level will still exist but be smaller.”

Lack of information on Himalayan glaciers is a serious problem. Kurt Lambeck, President of the Australian Science Academy, told Reuters, “There is no serious information on the state of melting in the glaciers in the Himalaya-Tibetan complex.” The high altitude and remoteness of the glaciers makes studying them difficult. To help fill in the gap, the Indian government recently established the National Institute of Himalayan Glaciology in Debra Dun, northern India.

Big Glaciers in the Himalayas

Gangotri Glacier is one of the largest in the Himalayas with an estimated volume of over 27 cubic kilometers. Located in Uttarkashi District, Uttarakhand, India in a region bordering Tibet, the glacier is one of the primary sources of the Ganges and is about 30 kilometers (19 miles) in length and and two to four kilometers (one to two miles) wide. Around the glacier are the peaks of the Gangotri Group, including several peaks well-known to mountaineers such as Meru, Thalay Sagar, Bhagirathi III and Shivling. The glacier flows roughly northwest, originating in a cirque below Chaukhamba, the highest peak of the group. The terminus of Gangotri Glacier, which is said to resemble a cow's mouth, is in Gomukh (Gaumukh, meaning cow face), which is about 19 kilometers (11.8 miles) from the town of Gangotri, the source of the Bhagirathi river, an important tributary of the Ganges. Gomukh is situated near the base of Shivling. [Source: Wikipedia]

Zemu Glacier is the largest glacier in the Eastern Himalaya. Located at the base of Kangchenjunga in Sikkim, India, it is about 26 kilometers (16 miles) in length and drains the east side of Kanchenjunga, the world's third highest mountain. The glacier is the source of water for numerous rivers. One of them is the Teesta River, where building a massive 3500 megawatt hydropower plant has been proposed. Currently 510 megawatt plant is situated on the river. One of the main issues about the plant is planned location in an earthquake-prone area.

The biggest glaciers in the Himalayan-Karakoram area are in Karakoram range in Pakistan and western China. Over 17,870 square kilometers (6,900 square miles) of the range is covered by permanent glaciers, an area almost the size of New Jersey. On the dry north side there aren't many glaciers, but on the southern side, where moisture-laden clouds crash into the peaks, you can find some of the longest valley glaciers in the world.

The steepness of the Karakorams causes some of these glaciers to advance with astonishing speed. In 1904, the Hasaababd Glacier surged downhill at a speed of 16 feet an hour, light-year speed for a glacier. In two months it advanced six kilometers (four miles). The Ghongkumdam glacier on occasion extends so far it blocks the Shyok River, creating a huge dam and reservoir. When the ice dam finally bursts, massive torrential floods sweep everything in its path.

Glaciers in Northern Pakistan

Northern Pakistan has some of the longest glaciers outside the Polar region: Siachen (72 kilometers), Hispar (61 kilometers), Biafo (60 kilometers), Baltoro (60 kilometers), Batura (64 kilometers), Passu (50 kilometers), Yenguta (35 kilometers), Chiantar (34 kilometers), Trich (29 kilometers) and Atrak (28 kilometers). [Source: Pakistan Tourism Development Corporation. tourism.gov.pk

Tim Craig wrote in the Washington Post: “With 7,253 known glaciers, including 543 in the Chitral Valley, there is more glacial ice in Pakistan than anywhere on Earth outside the polar regions, according to various studies. Those glaciers feed rivers that account for about 75 per cent of the stored- water supply in the country. [Source: Tim Craig, Washington Post, August 12, 2016]

“Weather changes have not seriously threatened the ice packs in Pakistan’s northernmost regions, where five of the world’s 14 highest peaks are located. Some researchers think that the glaciers in the Karakorum and Himalayan mountains in Gilgit- Baltistan may even expand as weather patterns shift and more precipitation falls over the highest peaks as snow. Many of Pakistan’s glaciers are also covered in silt and debris, which helps insulate them.

But farther south in the Chitral Valley, where most mountains are no higher than 22,000 feet, there is little doubt that the glaciers are under stress, researchers say. Siraj ul- Mulk, the 71-year-old owner of the Hindu Kush Heights Hotel in Chitral, has been trekking in a different part of northern Chitral since he was a young man. “It used to take me a whole day to cross the glacier,” he said. “Now, it will take me two hours.”

Glaciers in the Himalayas and Tibet and Their Ecological Importance

Glaciers in Tibet and great ranges of central Asia, including the Himalayas, make up the greatest concentration of ice outside the polar regions. These regions have the third largest number of glaciers after Antarctica and the Arctic. The Himalayan range contains about 15,000 glaciers, which store about 12,000 cubic kilometers (2,900 cubic miles) of fresh water. Some of biggest glaciers are Gangotri and Yamunotri (Uttarakhand, India) and Khumbu glaciers (Mt. Everest region in Nepal), Langtang glacier (Langtang region in Nepal) and Zemu (Sikkim). According to the World Wildlife Fund (WWF), China has 36,793 glaciers that cover 49,973 square kilometers and have an ice volume of 4,561 square kilometers. Most of these are in Tibet and the Himalayan region. [Source: Wikipedia]

Mountain glaciers are vital for providing a steady stream of water that feeds streams, rivers, lakes, agriculture and provides water for fish. The vast amount of water stored in Himalayan and Tibetan glaciers — which feeds great rivers like the Ganges, Indus, Brahmaputra, Mekong, and Yangtze — plays a crucial role in river flows, hydropower generation and agriculture. There is a lack of information on Himalayan glaciers. The high altitude and remoteness of the glaciers makes studying them difficult. To help fill in the gap, the Indian government recently established the National Institute of Himalayan Glaciology in Debra Dun, northern India.

Brook Larmer wrote in National Geographic, “With nearly 37,000 glaciers on the Chinese side alone, the Tibetan Plateau and its surrounding arc of mountains contain the largest volume of ice outside the polar regions. This ice gives birth to Asia's largest and most legendary rivers, from the Yangtze and the Yellow to the Mekong and the Ganges — rivers that over the course of history have nurtured civilizations, inspired religions, and sustained ecosystems. Today they are lifelines for some of Asia's most densely settled areas, from the arid plains of Pakistan to the thirsty metropolises of northern China 3,000 miles away. All told, some two billion people in more than a dozen countries — nearly a third of the world's population — depend on rivers fed by the snow and ice of the plateau region. [Source: Brook Larmer, National Geographic, April 2010]

“For thousands of years the glaciers have formed what Lonnie Thompson, a glaciologist at Ohio State University, calls "Asia's freshwater bank account" — an immense storehouse whose buildup of new ice and snow (deposits) has historically offset its annual runoff (withdrawals). Glacial melt plays its most vital role before and after the rainy season, when it supplies a greater portion of the flow in every river from the Yangtze (which irrigates more than half of China's rice) to the Ganges and the Indus (key to the agricultural heartlands of India and Pakistan)."

Himalayan Glaciers and Climate Change

The acceleration of ice loss in the Himalayas in recent decades has been graphically shown with satellite photographs. The Himalaya glaciers are expected to lose one third of their surfaces to climate change even if greenhouse gases are reduced and maybe lose two thirds if global warming continues at the same rate is today. The Nepal-based International Center for Integrated Mountain Development says, “Small glaciers below 5,000 meters above sea level will probably disappear by the end of the century, whereas larger glaciers well above that level will still exist but be smaller."

In recent years, scientists have monitored a notable increase in the rate of glacier retreat across the region as a result of climate change. For example, glacial lakes have been forming rapidly on the surface of debris-covered glaciers in the Bhutan Himalaya during the last few decades. Although the effect of this will not be known for many years, it potentially could mean disaster for the hundreds of millions of people who rely on the glaciers to feed the rivers during the dry seasons.

Bhadra Sharma and Kai Schultz wrote in the New York Times: “Glimpses of a warmer future are everywhere.In 2016, Nepal’s army drained a lake near Mt. Everest after rapid glacial melting threatened to cause a catastrophic flood downstream. A study released” in 2019 “found that the size of ponds on top of glaciers in the region — which can both signal melting and accelerate it — had rapidly increased over the past three years, far outpacing the rate of change from the first decade and a half of the 2000s. [Source: Bhadra Sharma and Kai Schultz, New York Times, April 5, 2020]

Lack of information on Himalayan glaciers is a serious problem. Kurt Lambeck, President of the Australian Science Academy, told Reuters, “There is no serious information on the state of melting in the glaciers in the Himalaya-Tibetan complex." The high altitude and remoteness of the glaciers makes studying them difficult. To help fill in the gap, the Indian government recently established the National Institute of Himalayan Glaciology in Debra Dun, northern India.

Avalanches in the Himalayas

Avalanche on Everest The largest natural avalanches occur in the Himalayas but no one has accurately measured them. Avalanches are landslide of ice and snow. Compared to mythical German monsters that fly without wings, sees without eyes and strikes without hands, they can reach speeds of 200mph; attain a mass of more than a million tons and produce forces 48 times stronger than those needed to demolish a frame house. Severe avalanche can snap trees like toothpicks, dump snow in 30-foot-high heaps and leave behind acres of destroyed buildings. [Source: National Geographic, September 1982]

Thousands of avalanches occur in the Himalayas, involving the movement of thousands of tons of ice and snow. Some have vertical displacements over 1,500 meters. Avalanches at Everest, Lhotse, Nuptse and other high peaks have killed many mountains climbers. Avalanches on snow-covered slopes — snow avalanches — generally occur in areas where there is a rapid accumulation of a huge mass of snow. The snow can not contain itself and begins to slide downhill at a very high velocity due to the increase in stress. The trigger can be wind, drifting snow, a loud noise, human activity, heavy snowfall in a short period of time, blasting, an earthquake, other seismic activity, even thunder. [Source: Thinkquest]

In the cold deserts, avalanches can cause widespread destruction and change land forms as snow slides tend to scour the mountainside, particularly when being accompanied by rock fragments. Kalpa, the headquarters of Kinnaur district in the Kinnaur Himalayas of India, was moved to Peo because of constant threats of these kinds of avalanches in winter.

Villages have been wiped out by avalanches. In 1838, Tunda village in Ladakh was completely destroyed by an avalanche. Many people died. Avalanches also block the flow of rivers and streams, creating temporary dams. When water backs up behind these dams and the water breaks through the dam, a huge tsunami-like flash flood or wave of water crashes down river valleys, smashing everything in their path. Avalanches have killed many people and washed villages in the Spiti area of Himachal Pradesh, India.

Large amounts of debris are sometimes carried by avalanches and this can damage forests and pastures. Trees can be broken at about chest height due to the force of the rushing snow. It is common see large tracts of avalanche-affected forests and pastures near snowline. Young saplings are the most prone to damage by avalanche.

Avalanches in Himachal Pradesh in the Indian Himalayas

Vishwa B.S.Chandel, of the Department of Geography at Panjab University, wrote: “Prior to 1971, the information regarding avalanche occurrence is very limited and therefore the historical reconstruction often presents a patchy picture. The Greater Himalayan areas of the state have historically been prone to avalanche hazard. There are two such recorded incidents, one in 1836 and another in 1863. Although it is difficult to decipher whether events of 1836 was an avalanche or intrusion of advancing glacier that blocked the river resulting in glacial lake outburst flood (GLOF). The other incident was a lethal snow storm that killed seventy two people in 1863. The gazetteers of Kangra District refer to series of avalanches in Kullu district where Phojal nullah near Manali was blocked and resultant flash flood devastated the downstream valley. Chander (1989) mentioned 9 events of avalanches in Kullu valley during 1935-1947. [Source: “Snow Avalanche as Disaster in Mountain Environment: A Case of Himachal Pradesh” by Vishwa B.S.Chandel, International Journal of Geomatics and Geosciences, Volume 6 Issue 2, 2015]

Since 1971, a number of damaging avalanche events has struck the state. There were six devastating incidents of avalanche during 1971-1979. Two porters got killed near Deo-Tibba at a height of 17,000 feet in an avalanche following heavy snowfall on 28 October 1972 while two climbers were killed in 1973 near Manali area and two more died at Arrang village of Lippa valley in Kinnaur district in 1975. There were two incidents of avalanche, first occurred in Pangi valley of Chamba district while other incident took place at Sagnam village in Pin valley of Lahaul & Spiti district in the end of March 1978. The official records state that these avalanches claimed 30 lives in Lahaul & Spiti district in 1978.

“The worst incident of avalanche occurred in the tribal district of Lahaul & Spiti during the winter of 1979. On 8th March 1979, about 75 persons were killed in devastating avalanches that occurred in different parts of Lahaul valley. The destruction continued for many days and as many as 237 people lost their lives in Lahaul valley. There were two incidents of snow-storm one at Shimla in 1971 and other near Manali in 1977 where two people died. The avalanche information extracted from newspaper archive of ‘The Tribune’ reveals that there were six incidents of avalanches during 1980s; two were in 1982, one in 1983, two in 1984 and one in 1988. These events claimed 21 lives out of which eleven were in Kinnaur, seven in Kullu and three in Chamba district. Besides these events, three incidents of snowstorm in 1981, 1982 and 1987 were reported claiming 21 lives out of which 7 were in Kullu, 9 in Shimla and 5 in Lahaul & Spiti districts, respectively.

“Seven incidents of avalanches occurred in 1990s, out of which five were in Lahaul & Spiti, and one each in Kullu and Kinnaur districts. All, except the one that hit the Kullu district near Rohtang pass in August, occurred during the winter months. There was at least one avalanche every year except 1990, 1993, 1994 and 1998. These events claimed 17 lives, 15 in Lahaul & Spiti and 2 in Kullu district.

“This next decade 2000-2009 recorded 15 events of avalanches in the state. In March 2002, avalanches killed 3 people in Namgia, Skiba and Nippa villages of Kinnaur district while in another incident at Tinku nullah blocked the river that created a huge lake. A huge avalanche struck four villages of Bharmaur in March 2003. During January 2006 avalanches damaged apple orchards in Kalichho village of Pangi valley and Nichar and Sangla valley of Kinnaur district. A series of avalanches struck the high altitude areas of Kinnaur, Lahaul & Spiti and Kullu districts in January 2008. In Kinnaur district avalanches struck on Sangla-Karcham road and Poari area causing damage to roads, houses and orchards. Two persons were killed in the Allain and Duhangan power project site at Prini near Manali. Another two persons were killed near the Surtang nullah near Sissu village and seven persons buried near Bharatpur in Lahaul & Spiti district. Apart from these events, three incidents of snow-storm occurred in the state. Shimla town was hit by a storm in January 2004 while Chitkul, Rakchham, Saring and Barseri areas of Sangla valley in Kinnaur were badly hit in January 2008. In another incident, a snowstorm near Rohtang at Rani Nala area of Kullu claimed 8 lives on 20 November 2009.”

Deadly Avalanche Kills 200 in the Indian Himalayas

In February 2021, around 200 people were after an avalanche in Tapovan, Uttarakhand in India’s Himalayan region created a huge wall of water that raged down a narrow river valley, breaking dams, sweeping away bridges, and trapping construction workers in tunnels. The incident occurred below Nanda Devi, India’s second-highest peak. Reuters reported: “India’s power minister, R.K. Singh, said an avalanche led to flash floods that swept away the small Rishiganga hydro electric project and damaged a bigger one further down the Dhauliganga river being built by state firm NTPC. Video footage showed a torrent of water, rock and dust sweeping down a mountain valley, where workers were still constructing and maintaining the dams. [Source: Alasdair Pal, Saurabh Sharma, Reuters, February 8, 2021]

“Experts said heavy snowfall followed by bright sunshine led to excessive snow-melt, triggering a chain reaction that led to the avalanche. “The area witnessed a heavy snowfall and then solar rays resulted in the melting of ice,” said Ravi Chopra, director of the non-profit People’s Science Institute in Uttarakhand state, where the incident took place. “On Sunday morning it was a bright, sunny day, and some of the snow started melting, which possibly led to an avalanche,” said Himanshu Thakkar, coordinator of the South Asia Network of Dams, Rivers and People, a research group.

“Incidents like this are rare so early in the year, but avalanches and flash flooding in the Himalayas are common during summer and monsoon months, as snow melt and heavy rains combine. In June 2013, record monsoon rains in Uttarakhand caused devastating floods that claimed close to 6,000 lives. A government report said while the disaster occurred as a result of natural hazards, human activity had contributed significantly. “The disaster revealed several infirmities in our preparedness, which need to be rectified at the earliest,” the report said, calling for limiting construction within flood plains and restrictions on blasting.

“In 2019, residents of Raini - one of the villages worst affected by Sunday’s avalanche - approached Uttarakhand’s top court, local media reported, asking the state government to investigate what they said were consistent breaches of the guidelines in the area. The court ordered local officials to investigate the claims. But experts said little has been done to curb the use of dynamite in construction, which significantly weakens the surrounding hills.“It would definitely have had a major impact,” Thakkar said. “There have been clear violations.” Om Prakash, Uttarakhand’s top government bureaucrat, declined to comment on claims guidelines had been breached.

Ganges and its tributaries: dependent on Himalayan glacier water

Dangerous Glacier Lakes in the Himalayas

Already increases in melting have caused some lakes in Nepal to overflow their banks and damage villages and hydroelectric facilities. Some farmers have prospered with a windfall of water that has flowed their way from melting glaciers.

Some Himalayan lakes are growing at a rapid pace as glaciers melt. The Tsh Rolpa lake in the Dolaka district in Nepal has grown from about a quarter of a square kilometer in the 1950s to 1½ square kilometers today. The Raphstreng Tsho glacial lake in Bhutan was 1.6 kilometers long and 80 meters deep in 1986 and today in two kilometers long and 127 meters deep.

Melting glaciers are producing huge glacier-fed lakes in valleys held back by weak natural earthen dams that are in danger of bursting and releasing torrents of water downstreamand threatening people who live in the river valleys downstream from the lake. Some call the danger “tsunamis from the sky.” Floods from such lake have killed in the past. One in 1994 killed 24 people in the river valley town of Punakha in Bhutan

Glacier Lake Outburst Floods and Their Dangers in the Himalayas

According to a paper by Georg Veh, Oliver Korup, and Ariane Walz: Sustained glacier melt in the Himalayas has gradually spawned more than 5,000 glacier lakes that are dammed by potentially unstable moraines. When such dams break, glacier lake outburst floods (GLOFs) can cause catastrophic societal and geomorphic impacts. The GLOF hazard may increase in regions that currently have large glaciers, but few lakes, if future projected ice loss generates more unstable moraine-dammed lakes than we recognize today. Flood peaks from GLOFs mostly attenuate within Himalayan headwaters, but can rival monsoon-fed discharges in major rivers hundreds to thousands of kilometers downstream. Projections of future hazard from meteorological floods need to account for the extreme runoffs during lake outbursts, given the increasing trends in population, infrastructure, and hydropower projects in Himalayan headwaters. [Source: “Hazard from Himalayan glacier lake outburst floods” by Georg Veh, Oliver Korup, and Ariane Walz, PNAS January 14, 2020 pnas.org ]

Monsoonal floods are among the most destructive natural hazards in the greater Himalayan region and the adjacent mountain ranges of the Hindu Kush, Karakoram, Nyainqentanglha, and Hengduan Shan. Regional projections for the lower Indus, Ganges, and Brahmaputra rivers hold that flood frequencies will rise noticeably in the 21st century, putting the livelihoods of 220 million people at risk.. In Himalayan headwaters, such prognoses have disregarded episodic, but potentially destructive, floods from the sudden emptying of moraine-dammed lakes. Such glacier lake outburst floods (GLOFs) occur largely independently of hydrometeorological floods, but can surpass their peak discharges by orders of magnitude in the upper river reaches.

Glacier lakes dammed by abandoned moraines are susceptible to outburst, triggered by ice or debris falls, strong earthquake shaking, internal piping, or overtopping waves that exceed the shear resistance of the dam. These triggers mostly happen unrecorded in remote terrain, eroding the impounding barriers within minutes to hours, and releasing sediment-laden floods that may travel >100 km downstream. With little to no warning, communities and infrastructure downstream have often been caught unprepared, suffering loss of human lives and livestock, and damage to roads, buildings, and hydropower facilities. An objective and reproducible hazard assessment of such dam-break floods is key to human safety and sustainable development, and is repeatedly emphasized in research and media coverage of atmospheric warming, dwindling glaciers, and growing meltwater lakes.

While the distribution and dynamics of moraine-dammed lakes have been mapped extensively in recent years, objectively appraising the current Himalayan GLOF hazard has remained challenging. The high-alpine conditions limit detailed fieldwork, leading researchers to extract proxies of hazard from increasingly detailed digital topographic data and satellite imagery. These data allow for readily measuring or estimating the geometry of ice and moraine dams, the possibility of avalanches or landslides entering a lake, or the water volumes released by outbursts. Ranking these diagnostics in GLOF hazard appraisals has mostly relied on expert judgment, because triggers and conditioning factors are largely unknown for most historic GLOFs.

Langmoche Flash-Flood, Khumbu Himal, Nepal

In August 1985, at least five people died — perhaps many more — in Langmoche in the Khumbu Himal region near Namche Bazar and Mt. Everest when a fragile wall of ice and debris surrounding a glacier gave way, releasing a wall of water 15 meters high that caused the Dig Tsho glacial lake to overflow. and send a wall of water down a flood plain where many of people lived. People, 14 bridges and houses were washed away and a hydro-electric plant was badly damaged.

Daniel Vuichard and Marcus Zimmermann of the University of Bern wrote: “The 4 August 1985 flash-flood originated in the sudden drainage of a moraine-dammed lake (named Dig Tsho) in the Langmoche Valley, one of the tributary valleys of the Bothe Kosi. This valley drains the eastern slope of a high ridge of ice-covered peaks and serves the local people as summer pasture for grazing yak. Three summer settlements between 4,100 and 4,200 meters above sea level are located on glacio-fluvial terraces below Dig Tsho; level land is used to grow potatoes and hay. The permanent Sherpa settlements are located in the Bothe Kosi Valley below 4,000 meters which also serves as the main trading route into Tibet (People's Republic of China). [Source: “The Langmoche Flash-Flood, Khumbu Himal, Nepal” by Daniel Vuichard and Marcus Zimmermann, Mountain Research and Development, Vol. 6, No. 1 (Feb., 1986), pp. 90-94, Published by: International Mountain Society]

“Below Namche Bazar, the main Sherpa settlement, the Bothe Kosi flows into the Dudh Kosi. Settlements along the Dudh Kosi are mainly located near or along the valley floor on alluvial cones and terraces. This is the main access route into the Khumbu from the south and, in recent decades, the trekking route to the Mt. Everest (Sagarmatha) base camp from the STOL air-strip at Lukla.

“Enormous amounts of water plummeted down the Bothe Kosi and Dudh Kosi on the afternoon of 4 August causing significant damage along more than 80 km of river course as far as the confluence of the Dudh Kosi with the Sun Kosi (Galay, 1985). The water originated in a dish-shaped basin elongated east-west between the sub-recent end moraines and snout of the Langmoche Glacier which formed a classic moraine-dammed lake. The Langmoche Glacier receives part of its mass from the periodic avalanching of the frontal face of a hanging glacier perched on the northeast face of Tangi Ragi Tau (6,940 meters). A large ice mass became detached from the granitic wall about the beginning of August following a long period of warm and clear weather in July. It overran the Langmoche Glacier and splashed into Dig Tsho Lake which was then full to its rim.

“The impact of the ice mass produced a tidal NWave and caused a significant rise in the lake level overtopping the moraine dam and cutting a V-shaped trench. This triggered the catastrophic drainage of the lake. A preliminary estimate provides 106 m3 of water draining from Dig Tsho in about 4 hours. This gives an average discharge of 500 cubic meters per second However, considering the character of the triggering mechanism, it is assumed that the initial peak discharge was probably at least 2,000 cubic meters per second

“Local witnesses reported that the surge front moved rather slowly down-valley as a huge "black" mass of water full of debris. There appear to have been several separate surges (for instance, the bridge at Jubing, 40 kilometers downstream, was washed out 90 minutes after passage of the first surge). The movement was of a rolling type, splashing from one river bank to the other. Shock waves overtopped the river banks. Trees and large boulders were dragged along and bounced around. The surge emitted a loud noise "like many helicopters" and a foul mud-smell.The valley bottom was wreathed in misty clouds of water vapour; the river banks were trembling; houses were shaking; the sky was cloudless.

In 2016, Nepal’s army drained a lake near Mt. Everest after rapid glacial melting threatened to cause a catastrophic flood downstream.

Image Sources: Wikimedia Commons; Except Everest climbing routes, Luca Galuzzi and Alan Arnette, Wikimedia Commons

Text Sources: New York Times, Washington Post, Los Angeles Times, Lonely Planet Guides, Library of Congress, Nepal Tourism Board (ntb.gov.np), Nepal Government National Portal (nepal.gov.np), The Guardian, National Geographic, Smithsonian magazine, The New Yorker, Time, Reuters, Associated Press, AFP, Wikipedia and various books, websites and other publications.

Last updated February 2022