Glacial Lake Outburst Floods (GLOFs) : GS TIMES IAS-PCS

Why in News?
Union Home Secretary Govind Mohan chaired a meeting on September 3, 2026, in New Delhi to review the preparedness of Himalayan States/UTs against Glacial Lake Outburst Floods (GLOFs) and snow avalanches. The meeting focused on early-warning systems, monitoring of vulnerable glacial lakes, evacuation preparedness and strengthening disaster-response mechanisms.

What is a GLOF?

A Glacial Lake Outburst Flood (GLOF) occurs when water stored in a glacial lake is suddenly released due to the failure of a moraine or ice dam.
It is a rapid-onset flood, generally lasting from hours to days, and can generate extremely high downstream discharges.

Types of Glacial Lakes

1. Moraine-dammed lakes

Form when a retreating glacier leaves behind a moraine that acts as a natural dam.
Meltwater accumulates between the retreating glacier and the proglacial moraine.
Landslides, ice/rock avalanches, glacier fragmentation and displacement waves can destabilise the dam and trigger a GLOF.
These are common in the Hindu Kush Himalaya.

2. Ice-dammed lakes

Form when a glacier blocks the natural drainage of meltwater.
Their formation and size are closely linked to glacier mass balance and climate conditions.
They can occur where a glacier advances or thickens sufficiently to block drainage.

Sikkim: Proposed Mitigation Measures

Following the 2023 South Lhonak GLOF, Sikkim has proposed three major engineering interventions:

Solar-powered pumping system at Shako Chho.
Flood-retention structure at Dolma Sampa in the Lhonak Valley.
Safety wall at the outlet of the Gurudongmar Lake complex.

2023 South Lhonak GLOF

Sikkim experienced a major GLOF in October 2023 following the bursting of South Lhonak Lake.
It caused a sharp rise in the Teesta River, resulting in extensive downstream destruction and loss of lives.

Why is the Risk Increasing?

According to ICIMOD, climate change can:

Accelerate glacier melting and retreat.
Create new glacial lakes.
Expand and sometimes merge existing lakes.
Increase the volume of water available for potential floods.
Increase the probability and potential magnitude of GLOFs.

Thus, climate change + expanding glacial lakes + growing downstream exposure is creating a major disaster-risk challenge in the Himalayas.

Role of ISRO

ISRO/Department of Space (DoS) is undertaking R&D to strengthen space-based early-warning systems for GLOFs, extreme weather events and landslides.

Satellite-based observations can help in: