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Glacier Lake
Outburst Floods

Learn what are GLOFs and why they are a growing threat to the region
  • What are Glacial Lake Outburst Floods?
A Glacial Lake Outburst Flood (GLOF) is a catastrophic release of water from a glacier lake, i.e. a water reservoir that has formed either at the side, in front, within, beneath, or on the surface of a glacier. These lakes are typically dammed by debris, bedrock or glacial ice.

Unstable Glacier Lakes

Many lakes form behind weak moraines or melting ice dams. They may fill quickly and fail without warning, especially after heavy rain or heatwaves.

High-Impact Floods

GLOFs can mobilise rocks, ice, and mud, damaging homes, roads, and farmland. Their force often exceeds that of seasonal floods.

Cross-Border Hazards

GLOFs can travel over 100 km, crossing borders, highlighting the need for regional cooperation.
  • How Do Ice-Dammed Lakes Form?
Ice-dammed lakes develop when advancing or retreating glaciers block side valleys or low-lying areas. While some of these lakes are remnants of the Ice Age, others are actively forming today as glaciers melt. Some ice-dammed glacier lakes form and drain repeatedly. For instance, Lake Merzbacher in Kyrgyzstan, which drains annually, is one of the most studied ice-dammed lakes globally.
  • Outbursts from Supraglacial, Subglacial, and Other Lakes
Lakes can also form on the glacier’s surface (supraglacial), within the ice, or beneath it (subglacial). These water bodies may drain suddenly due to warm weather and subsequently induced enhanced glacial melt or heavy rainfall. In the Tien Shan region, frequent monitoring is critical for identifying rapidly evolving dangerous situations. In Central Asia, such dynamic lakes, known as “non-stationary” lakes, present unique challenges for early warning and response strategies.
GLOFCA Theme GLOF – Glacier Lake Outburst Floods
  • Moraine-Dammed Lakes:
    A Common Risk
As mountain glaciers retreat, they often leave behind unstable ridges of rock and debris called moraines. These can act as natural dams, holding back large volumes of meltwater. Some of these lakes are enormous, with volumes exceeding 100 million m³ and depths of over 200 meters. But intense rainfall, snowmelt, landslides, or earthquakes can destabilise them, triggering powerful floods. Tsunami waves caused by landslides into lakes can also overtop moraine dams, leading to floods without destroying the dam itself, leaving a threat of secondary events. Such lakes are among the most common and hazardous in Central Asia.

  • Characteristics of GLOFs

Once triggered, GLOFs can mobilize vast amounts of debris and transport massive boulders, especially in steep mountain rivers. This is particularly common in floods from moraine-dammed lakes, which often evolve into debris or mudflows. Compared to regular seasonal floods, GLOFs generate significantly higher discharge rates and erosive power, resulting in greater destruction. Although their intensity typically decreases downstream, GLOFs have been known to travel over 100 kilometres, sometimes affecting areas across national borders (transboundary GLOFs). Secondary hazards such as riverbank erosion, channel blockages, and downstream lake impacts can further compound the risks.

  • Future Risks and the Need for Mitigation

With climate change accelerating glacier melt, more glacial lakes are forming at higher altitudes. At the same time, communities, tourism, roads, and hydropower facilities are expanding into mountain valleys. This rising exposure means the risk of GLOFs is growing. Proactive measures, such as hazard assessments, early warning systems, and regional cooperation, are essential to protect lives and livelihoods.

Source: GAPHAZ 2017

News

Stay informed with the latest developments in GLOF research, policy initiatives, and community resilience projects across Central Asia. Our regular updates connect you with the region’s most pressing glacier hazard challenges and solutions.
Community
Uzbekistan
31 July 2025

Continuing Disaster Risk Education in Uzbekistan’s Mountain Villages

In the middle of July 2025, the GLOFCA project returned to the pilot villages of Pskem and Tepar in Uzbekistan’s Bostanlyk District to continue building local knowledge on glacier-related hazards.
Event
International
5 June 2025

GLOFCA Showcases Regional Progress at High-Level Glacier Conference in Tajikistan

Event
Tajikistan
23 March 2025

GLOFCA Participates in High-Level Glacier Preservation Conference in Tajikistan

On 20–21 March 2025, the GLOFCA project was represented at the International Scientific and Practical Conference on “Preservation of Glaciers – The Basis for Ensuring Water, Food, Energy, and Environmental Security”, held in Dushanbe, Tajikistan.