Multi-Source Remote Sensing and Hydro-Geomorphic Dataset for Assessing Triggering Mechanisms of October 2023 South Lhonak GLOF, Sikkim Himalaya

Data Abstract: This dataset supports the investigation of triggering mechanisms behind the October 3–4, 2023 Glacial Lake Outburst Flood (GLOF) from South Lhonak Glacial Lake (SLGL) in the Sikkim Himalaya. The dataset integrates multi-source remote sensing observations, interferometric coherence analysis, geomorphometric parameters, and hydro-climatic data to systematically evaluate potential GLOF triggers and eliminate non-contributing factors. The dataset comprises eight structured tables documenting key parameters associated with possible GLOF triggering mechanisms, including upstream lake influence, glacier calving, slope instability, hydrostatic pressure, outlet erosion, seismicity, and hydrometeorological conditions. Specifically, it includes (i) characteristics of the upstream North Lhonak Glacial Lake (NLGL) and its connectivity to SLGL, (ii) glacier–lake interaction metrics such as calving activity and glacier velocity, (iii) slope geometry and evidence of moraine instability, (iv) morphometric and volumetric properties of the moraine dam, (v) outlet channel characteristics and erosion susceptibility, (vi) regional seismic hazard indicators, and (vii) long-term temperature and precipitation trends derived from multiple datasets. Additionally, (viii) monthly cumulative precipitation data from GPM and MERRA-2 datasets (2022–2024) provide insight into antecedent hydrometeorological conditions prior to the lateral moraine collapse. The list of Tables are included within this abstract below. The dataset demonstrates that while several potential triggers exist, most factors, including upstream lake outburst, seismic activity, and extreme precipitation, had negligible or no direct influence on the event. Instead, the data support the interpretation that progressive slope saturation, driven by increased surface runoff and subsurface seepage, destabilized the left lateral moraine and culminated in a large landslide (~13.1 ± 2.7 × 106 m3), which ultimately triggered the GLOF. This dataset is valuable for hazard assessment of potentially dangerous glacial lakes (PDGLs), enabling reproducible evaluation of GLOF triggering mechanisms in any remote, data-scarce high-mountain environments. Keywords: Glacial Lake Outburst Flood (GLOF); South Lhonak Glacial Lake; Landslide triggering; Moraine stability; Interferometric coherence; Hydro-climatic variability; Hazard assessment; Sikkim Himalaya. Related Research Article: This dataset is part of our published research article: Vilímek, V., Kropáček, J., Chowdhury, A., Baťka, J., De, S.K., 2026.Analysis of triggering factors behind the October 2023 South Lhonak GLOF event in the Sikkim Himalaya using multiple remote sensing data. Geomatics, Natural Hazards and Risk, 17(1), 1–29. https://doi.org/10.1080/19475705.2026.2625407.