Environment

Last June and August, two villages, La Bérarde and Thame, were entirely engulfed. One in the French region of Isère, the other in Nepal, on the doorstep of Mount Everest. The cause? Glacial lakes, bodies of water that form at the foot of glaciers and rest on dams. These dams can break at any time. 

There are several types of suspended lakes. There are those on the flanks and at the lower end of a glacier, directly linked to global warming. These are the result of glacial thinning and retreat. And then, there are those formed on the surface of a glacier or within it, which aren't directly linked to climate change. 

According to Christian Vincent, glaciologist at the Institut des Géosciences de l'Environnement (IGE) in Grenoble, glacial lakes have multiplied in the high mountains, precisely because of glacial retreat, but “aren't necessarily dangerous”. “Using satellite imagery, they're easy to spot, but it's impossible to know whether they represent a threat,” he explains. In order to find out, it's then necessary to carry out certain field studies, requiring substantial funding. Each case can evolve in a very short space of time. 

Why are some lakes more dangerous than others? Because of the dam that holds them back. If the dam is fragile, it could burst at any moment, causing a sudden emptying. Thousands of cubic metres of water would then pour into the valleys, causing torrential flooding, reports the website Mon séjour en Montagne. Christian Vincent concludes: “If there are populations or infrastructures downstream, glacial lakes are a very big threat”. 

(MH with AsD - Source: Mon séjour en Montagne - Illustration: Unsplash)