As glaciers melt lakes often form at their bases. A combination of water build up and geological instability can lead to glacial lake outburst floods (GLOF). A global study on the phenomenon estimates that around 700,000 people in Switzerland could potentially be exposed to the risks associated with these floods.
These floods can be highly destructive and can arrive with little prior warning, causing significant damage to property, infrastructure, and agricultural land, resulting in extensive loss of life, said the authors. Over the last 70 years, several thousand people have been killed by such floods.
Since 1990, the number, area, and volume of glacial lakes globally has grown by around 50%. In addition, population growth, agricultural intensification and the expansion of infrastructure and hydroelectric power has increased the potential for damage and loss of life, said the report.
The most at risk regions globally are the Himalayas and Andes. India, Pakistan, Peru, and China account for more than half of the population at risk. In total, 90 million people across 30 countries live in 1,089 basins containing glacial lakes. 15 million (16.6%) live within 50 km of a glacial lake and 1 km of potential glacial lake flood runout tracks.
Of the 30 nations covered by the study, the most vulnerable nations include Afghanistan, Pakistan, Nepal, Tadjikistan, Kyrgyzstan, Bolivia, Peru, Colombia, India, Uzbekistan, Mongolia, Russia and China. Switzerland has the second lowest vulnerability to the risks of glacial lake floods after New Zealand.
Vulnerability is combined with risk exposure and lake conditions to arrive at a composite danger score.
The regions exposed to the highest danger are south of the Alps, shown in red on the image above. The danger lowers as the shading becomes lighter, with light blue being the lowest. Cantons exposed to glacial lake danger include Valais, parts of Vaud, parts of Geneva, Ticino, parts of Bern, the cantons in central Switzerland, Graubunden and Zurich.
Glacial lake study (in English)