Bossons glacial lake: rock excavation work to carry out in June


The glacial lake formed in 2018 at the foot of the Bossons glacier expands as it melts. To avoid a potentially excessive emptying and a very dangerous torrential flood, the municipality of Chamonix will undertake excavation work during the month of June 2022.

Lac glaciaire des Bossons :  des travaux de déroctage menés en juin
Lac glaciaire des Bossons :  des travaux de déroctage menés en juin


The lake has becomed a curiosity in the Chamonix valley, last summer hikers already photographed the lake considered a photogenic natural cavity.

But as the Bossons glacier melts, the expanse of water observable at an altitude of 1695 meters develops to the point of worrying the town hall of Chamonix and the prefecture, which are closely monitoring its evolution. Glaciologists have studied the lake and their work has highlighted its rapid growth spurt.

According to Le Dauphine, last July the volume of the lake was estimated at 3,700 m³. But because the flow from its main outlet remains lower than the incoming flows, the periglacial lake swells, especially in summer during the melting period.

Risk of shifting the flow towards the Bossons torrent

According to the Institute of Environmental Geosciences (IGE), the Bossons glacier decreases in this area by 4.5 to 6.5 meters per year. A parameter that suggests that as of next fall, the lake could reach 20.000 m³, five times its volume recorded last summer.

"Measurements made using radar and probes have shown that the lake is now blocked by the glacier," explained Claude Jacot, Chamonix deputy in charge of security and the mountain. “But when it is going to withdraw, the flow risks switching to the left bank towards the Bossons torrent and its district, because the slope of the rocky bed is oriented in this direction. »

Rock excavation work during the month of June 2022

The municipality of Chamonix has decided to undertake excavation work during the month of June to limit the impact of an unpredictable sudden emptying.

A spider excavator will soon be mounted by helicopter to move some large blocks around the current spillway, in order to lower the level of the lake and reduce the danger.

An operation that will allow a partial purge of the lake. Monitoring will be carried out on the lake and the glacier tongue using new probes, radars and drones.

The total cost of these interventions is estimated at 128.000 euros.

Source: @Le Dauphiné Libéré

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