Abstract ID: 3.10174 | Accepted as Talk | Talk/Oral | TBA | TBA

A proglacial lake started to form since 2015 on the right side of the Bossons Glacier (French Mont Blanc Alps). Given this lake was dammed by the glacier on its left bank, it has expanded and deepened over time. As the intensity and probability of a sudden drainage through a subglacial channel have increased over time, it has been decided to drain artificially the lake during the summer of 2023. To achieve this, an overflow channel was mechanically dug on the glacier to initiate the drainage, which then took place naturally by incising the channel into the ice thanks to the thermal erosion induced by the water flow. The entire lake was emptied in less than a week by incising a channel more than 6 m deep in the glacier. As our ability to predict the course of such overflow drainage (maximum discharge and duration of drainage) was limited, we took advantage of the opportunity to investigate the breaching of an ice dam. For this purpose, we deployed a number of instruments in the channel for the duration of the drainage. The data acquired during the lake drainage and their analysis will be presented. Our results are then compared to the well-documented drainage of Rochemelon lake (2005, French Alps) and Plaine Morte lake (2019, Switzerland Alps).