Glacial lake outburst flood
[1][2] A 2023 study found 15 million people at risk from this hazard, mostly in China, India, Nepal, Pakistan, and Peru.
Jökulhlaup is an Icelandic term that has been adopted into the English language, originally referring only to glacial outburst floods from Vatnajökull, which are triggered by volcanic eruptions, but now is accepted to describe any abrupt and large release of sub-glacial water.
Catastrophic failure of the containing ice or glacial sediment can release this water over periods of minutes to days.
The United Nations has a series of monitoring efforts to help prevent death and destruction in regions that are likely to experience these events.
The Tsho Rolpa glacier lake is located in the Rolwaling Valley, about 110 kilometres (68 mi) northeast of Kathmandu, Nepal, at an altitude of 4,580 metres (15,030 ft).
[7] In June 2013, Kedarnath in Uttarakhand witnessed flash floods along with a GLOF caused by Chorabari Tal, killing thousands of pilgrims, tourists and residents who came to visit the place.
In 2017, a "Scaling up of Glacial Lake Outburst Flood Risk Reduction in Northern Pakistan Project" was continued.
[12] Even though GLOF events have been occurring in Nepal for many decades, the 1985 Dig Cho glacial lake outburst has triggered detailed study of this phenomenon.
In 1996, the Water and Energy Commission Secretariat (WECS) of Nepal reported that five lakes were potentially dangerous, namely, Dig Tsho, Imja, Lower Barun, Tsho Rolpa, and Thulagi, all lying above 4100 m. A 2001 study done by ICIMOD and UNEP reported 20 potentially dangerous lakes in Nepal.
The Kreditanstalt für Wiederaufbau, Frankfurt am Main, the BGR (Federal Institute for Geosciences and Natural Resources, Germany), in cooperation with the Department of Hydrology and Meteorology in Kathmandu, have carried out studies on the Thulagi Glacier and have concluded in 2011 that even assuming the worst case, a disastrous outburst of the lake can be excluded in the near future.
According to the report of the Hydrological Department of Tibet in 2006, if a GLOF had occurred at the two lakes, 23 towns and villages, where more than 12,500 people live, would have been endangered.
[15] A major GLOF was reported in 1978 in the valley of the Shaksgam River in the Karakoram, a part of historic Kashmir, ceded by Pakistan to China.
After the flooding, some icebergs 10 metres (33 ft) high could be seen on the banks of the river where the glacier run had left them behind (see also Mýrdalsjökull).
The peak water release from a lake that develops around the Grímsvötn Volcanic Crater in the center of the Vatnajökull ice cap generates flows that exceed the volume of the Mississippi River.
The Strait of Dover is thought to have been created around 200,000 years ago by a catastrophic GLOF caused by the breaching of the Weald-Artois Anticline, which acted as a natural dam that held back a large lake in the Doggerland region, now submerged under the North Sea.
As well as destroying the isthmus that connected Britain to continental Europe, the flood carved a large bedrock-floored valley down the length of the English Channel, leaving behind streamlined islands and longitudinal erosional grooves characteristic of catastrophic megaflood events.
[19] However, the cone began to crack on the morning of 16 June and at 16:30 the ice dam broke sending 18 million m3 of flood waters into the valley below.
[19] During the late Quaternary, ancient Lake Atna in the Copper River Basin may have generated a number of glacial outburst floods.
Lake George might resume annual floods if the glacier thickens again and blocks the valley (Post and Mayo, 1971).
The immense floods scoured the Columbia Plateau as the water raced toward the ocean, resulting in the Channeled Scablands topography that exists today across Central and Eastern Washington.
This is an extremely rare occurrence in the Canadian High Arctic, where most glaciers are cold based, and ice-dammed lakes typically drain slowly by overtopping their dams.
