VidBodh AcademyThe art and science of civil services preparation
Student login

Environment › Climate science

Cryosphere, oceans and sea level

Ice, oceans and the rising sea: glaciers and glacial lakes, permafrost, polar ice, ocean heat and acidity, and sea level. Prelims has asked which rivers rise from which Himalayan glaciers, and about the source and course of the Teesta.

Showing 1 of 5 subjects, those that changed from 16 to 31 August 2026.Show all

The Nepal flood of August 2026

Copy link to The Nepal flood of August 2026

Prelims and Mains

On 26 August glacier ice and bedrock broke away on Langtang Lirung near the Nepal Tibet border, and what followed was a cascading hazard rather than a single flood.

  • A glacial lake outburst flood begins when a lake's natural dam fails; this one began instead with a slope failure of ice and rock, which is why it is not called one.
  • A debris flow erodes riverbanks and gains mass and momentum as it travels, which is why experts called this one a sediment bomb.
  • The flow ran nearly 100 km, and Nepal counted about 1,340 dead by 7 September.
  • About a tenth of Nepal's hydropower capacity, 431 MW, was hit by the single event.

  1. Collapse

    Glacier ice and bedrock break away on Langtang Lirung.

  2. Temporary dam

    Debris blocks the Lhende Khola in Tibet, then fails within minutes.

  3. Bhote Koshi

    The surge sweeps back into Nepal, gathering sediment.

  4. Trishuli

    The Trishuli rises by up to 9 metres in under 30 minutes.

  5. Into India

    The flow joins the Narayani system and enters India as the Gandak.

From the Indian Express interview with Austin Lord, 31 August 2026, and Frontline, 1 and 7 September 2026

What changed

  1. 1 Sep 2026

    Frontline, 1 Sep 2026: India can see the danger in the Himalaya. Can it manage the risk? (opens in a new tab)

  2. 28 Aug 2026Updatealso in newsnewly added

    • The cause was contested early on: the United States Geological Survey pointed to a glacial collapse, while ICIMOD examined an avalanche of ice and rock. A barrier lake then formed near the border with China, a second and delayed hazard.
    • A separate study records a 525 per cent rise in the number of glacial lakes in Himachal Pradesh between 1990 and 2024.

    Frontline, 28 Aug 2026: A sudden flood on a Bhote Koshi tributary kills over 780 people in Nepal and Tibet, and the cause is still contested between a glacial lake burst and an ice-rock avalanche. (opens in a new tab)

Background reading: The Indian Express, 31 Aug 2026: 'Needles in haystacks': An expert explains the challenge of early warnings in the Himalayas (opens in a new tab)

Also filed elsewhere

  • Hydropower in the Himalaya · on Wind, hydro and other renewables

    The mountains hold most of the fall a turbine wants and most of the hazard a project cannot survive.