The devastating floods in Nepal in August have drawn renewed attention to the growing risks posed by unstable glaciers and glacial lakes in the high mountains. The disaster, which followed a glacial collapse near the Nepal-Tibet border, killed around 1,400 people and caused extensive destruction along the Lhende Khola River.
The event has also raised concerns about other mountainous regions where rising temperatures are destabilising glaciers and increasing the possibility of sudden floods.
Glacial collapses can trigger powerful floods when large quantities of ice, rock and water suddenly move downhill. In areas where communities, roads, bridges and hydropower infrastructure are located in narrow valleys below glaciers, such events can leave little time for evacuation.
Scientists have increasingly warned that climate change is altering mountain environments. Rising temperatures can accelerate glacier melt weaken frozen slopes and increase the volume of water stored in glacial lakes. As glaciers retreat, unstable lakes can form behind natural dams made of ice, rock and debris.
When such barriers fail the resulting glacial lake outburst flood can send enormous volumes of water downstream, potentially affecting communities many kilometres away.
The Nepal disaster has highlighted the Himalayan region as a major area of concern because of its rapidly changing glaciers and densely populated valleys. But experts say the threat is not limited to the Himalayas.
Other mountain regions around the world also contain unstable glaciers and glacial lakes that could pose risks to people and infrastructure downstream. These include parts of the Andes, Central Asia and other high altitude regions where warming temperatures are changing long established patterns of ice and water.
The danger is particularly significant where communities have expanded into valleys that were historically exposed to fewer large floods. Roads, bridges and hydropower projects can also increase the potential economic impact of a sudden release of water and debris.
Scientists are therefore increasingly focusing on monitoring vulnerable glaciers and glacial lakes. Satellite observations, aerial surveys, ground based instruments and early warning systems can help identify changes in glacier movement, lake size and slope stability.
Early warnings can be particularly important in remote mountain areas where evacuation routes may be limited and emergency services can take longer to reach affected communities.
The Nepal floods have consequently become a warning about the wider consequences of a warming mountain environment. While scientists cannot predict every individual glacier collapse, identifying vulnerable locations and improving monitoring and emergency response systems could help reduce the human impact of future disasters.
The challenge is becoming more urgent as climate change continues to reshape high altitude landscapes. The Himalayas and other mountain ranges are likely to remain areas of close scientific attention as researchers work to determine where the next major glacial disaster could occur.