Modeling glacial lake bathymetry and water storage from UAV data in proximity to former Gornersee, Monte Rosa Massif, Western Alps

Abstract

Formation and sudden drainage of glacial lakes pose increasing hazards in high-mountain regions, threatening downstream communities, infrastructure and ecosystems. Accurate bathymetric reconstruction and lake volume estimation are crucial for flood modeling, hazard assessment, and monitoring climate-driven glacial lake dynamics. This study uses a recently drained lake at the margin of Gornergletscher, Monte Rosa Massif, Western Alps, to reconstruct its bathymetry and estimate its volume by combining a high-resolution digital elevation model (DEM) from low-cost uncrewed aerial vehicle (UAV) imagery with multispectral Sentinel-2 data. The UAV data were used to generate an orthomosaic and a high-resolution DEM of the empty lake basin. Lake extents corresponding to five filling stages, together with the DEM, enabled pixelwise depth estimation, yielding a mean lake depth for maximal filling of 21.94 m and an estimated corresponding water volume of 0.298 +/- 0.11 & times; 10(6) m3. Field observations indicated direct glacier contact and subglacial drainage through vertical conduits. Sentinel-2 also revealed smaller lakes in 2017 and 2018. Comparative analysis of climate variables from lake (2017, 2018 and 2022) and no-lake (2019-21) years highlighted higher April-June temperatures as the dominant factor controlling lake formation. This study demonstrates the value of integrating UAV three-dimensional (3-D) terrain modeling with satellite remote sensing for high-resolution glacial lake monitoring.