GLOF: Recent Examples From 2021 to 2025
A dated list of recent glacial lake outburst floods, from South Lhonak Lake in Sikkim (October 2023) to the Rasuwa flood on the Nepal-Tibet border (July 2025), plus Alaska's annual Mendenhall floods and the Hunza bridge collapse in Pakistan. Includes what each event destroyed, what triggered it, and which famous disasters were not actually GLOFs.
A dated list of recent glacial lake outburst floods, from South Lhonak Lake in Sikkim (October 2023) to the Rasuwa flood on the Nepal-Tibet border (July 2025), plus Alaska's annual Mendenhall floods and the Hunza bridge collapse in Pakistan. Includes what each event destroyed, what triggered it, and which famous disasters were not actually GLOFs.
The recent GLOFs worth knowing
The most quoted recent example is South Lhonak Lake in north Sikkim, which burst on the night of 3-4 October 2023 and destroyed the 1,200 MW Teesta-III dam at Chungthang downstream. Nepal has had two since: a flood from lakes above Thame village in the Everest region on 16 August 2024, and a flood down the Bhotekoshi at Rasuwagadhi on 8 July 2025 that wrecked the Nepal-China Friendship Bridge. Outside the Himalaya, the town of Juneau in Alaska has now been flooded by Suicide Basin at Mendenhall Glacier in five of the last six summers, with a new record water level in August 2025.
Those four cover most of what an examiner or a reader actually wants. The table below adds the rest of the useful ones.
| Date | Where | Source | What happened |
|---|---|---|---|
| 4 Oct 2023 | Sikkim, India | South Lhonak Lake | Teesta-III dam at Chungthang destroyed; roughly 55 dead and dozens never found |
| 16 Aug 2024 | Thame, Solukhumbu, Nepal | Glacial lakes above Thame | Around half the village destroyed, including the school and health post; no deaths |
| 8 Jul 2025 | Rasuwa, Nepal-Tibet border | Supraglacial lake in Tibet | Friendship Bridge and Rasuwagadhi hydropower works swept away; at least 9 dead, about 19 missing |
| 7 May 2022 | Hunza, Gilgit-Baltistan, Pakistan | Shisper Glacier lake | Hassanabad bridge on the Karakoram Highway collapsed on camera; two small power houses lost |
| Aug 2023, 2024, 2025 | Juneau, Alaska, USA | Suicide Basin, Mendenhall Glacier | Record lake crests three years running; roughly 290 homes damaged in 2024 |
| 16-17 Jun 2013 | Kedarnath, Uttarakhand | Chorabari Lake | Lake breach on top of extreme rain; thousands killed |
Sikkim 2023: the one to study in detail
South Lhonak is a moraine-dammed lake at about 5,200 m that had been growing for decades as the glacier behind it retreated. It lost roughly two thirds of its area in a few hours. Tens of millions of cubic metres of water went down the Teesta and hit Chungthang, where the concrete dam failed in minutes and released more water still.
The trigger was not simply rain. A 2024 study in Science attributed it to a large landslide off the frozen lateral moraine, roughly 15 million cubic metres of rock and ice dropping into the lake and generating a wave that overtopped the dam. That matters, because it means a lake can be stable for years and still fail in a single night with no meteorological warning. Sikkim had even run a siphoning trial at South Lhonak years earlier to lower the water level. It was not enough.
Nepal, twice in twelve months
Thame, in August 2024, is the cleanest recent case of a GLOF with no rain to muddy the story. Small lakes above the village drained, the debris flow followed the old channel, and the village was hit in daylight while people were awake. Buildings went. Nobody died.
The Rasuwa flood of July 2025 was different and more awkward politically. The water came from a supraglacial lake on the Tibetan side, so Nepal had no way to monitor it and no warning at all. Trucks parked at the dry port were carried off. Two hydropower projects on the Bhotekoshi were badly damaged, and the main trade route to China closed. When the hazard sits across a border, monitoring is a diplomatic problem before it is a technical one.
Cases outside the Himalaya
Alaska is the odd one out because its GLOFs are annual and expected. Suicide Basin, an ice-marginal basin beside Mendenhall Glacier, fills each summer and drains under the ice into Mendenhall Lake and the river through Juneau. The 2024 flood set a record at 15.99 feet, then August 2025 beat it at about 16.65 feet, though temporary barriers cut the damage that year. A predictable GLOF is still a GLOF, and Juneau shows what living with one looks like.
Peru gives the legal example. Lake Palcacocha above Huaraz burst in 1941 and killed something like 1,800 people, and the lake is dangerous again today. A Huaraz farmer sued the German utility RWE over the cost of protecting his home. In May 2025 a court in Hamm dismissed his specific claim but accepted the principle that a major emitter can in law be liable for a distant climate risk. Cited often, and worth one line in an answer on climate litigation.
Two events that get mislabelled
The Chamoli disaster of 7 February 2021 killed around 200 people and destroyed the Rishiganga and Tapovan projects in Uttarakhand. It was not a GLOF. A slab of rock and ice, roughly 27 million cubic metres, broke off near Ronti Peak and turned into a debris flow on the way down. No lake burst.
Kedarnath 2013 is the reverse case, half right. The Chorabari Lake breach on 17 June 2013 was a genuine lake outburst, but it landed on top of three days of record rainfall and swollen rivers, so the flood was not caused by the lake alone. Say cascading hazard, not GLOF, and you will be accurate. The pattern across all these events is that the water is rarely the first thing to move. Rock moves, or ice moves, and the lake is only the amplifier.
FAQs
Which was the most recent GLOF?
The most recent widely reported one is the 8 July 2025 flood down the Bhotekoshi at Rasuwagadhi on the Nepal-Tibet border, caused by a supraglacial lake draining in Tibet. Alaska's Mendenhall Glacier also flooded Juneau in August 2025, setting a record lake level of about 16.65 feet.
How many glacial lakes in India are considered dangerous?
Central Water Commission monitoring covers several hundred glacial lakes above 0.05 sq km in the Indian Himalaya, and around 190 of them are classed as high risk under the National Disaster Management Authority's GLOF risk reduction programme launched in 2024. Sikkim, Uttarakhand, Himachal Pradesh, Ladakh and Arunachal Pradesh hold most of them.
Does India have a GLOF early warning system now?
Yes, partly. After the 2023 Sikkim disaster, NDMA began installing automated weather stations and water level sensors at high-risk lakes, and Sikkim has restored warning equipment on the Teesta. Coverage is still thin, and lakes across the border in Tibet or Nepal are not monitored by India at all.
Why are GLOFs becoming more frequent?
Glaciers are retreating and leaving meltwater trapped behind loose moraine dams, so the number and size of glacial lakes keeps rising. Warming also thaws the permafrost holding steep rock and ice in place, which is what supplies the landslides and avalanches that trigger most outbursts.
What is the difference between a GLOF and a jokulhlaup?
A jokulhlaup is the Icelandic term for a glacier outburst flood, often used specifically for water released from under or inside a glacier, sometimes by volcanic heat as at Grimsvotn. A GLOF usually means a surface lake dammed by moraine or ice that breaches. The two overlap and the words are often used interchangeably.
Was the Blatten disaster in Switzerland a GLOF?
No. On 28 May 2025 the Birch Glacier collapsed and buried most of the village of Blatten in the Lotschental. The debris then dammed the Lonza river and created a lake, so the risk that followed was a dam-break risk rather than a glacial lake outburst.