The effects of snowmelt on loess landslides in Tian Shan, China

The Zeketai River Basin of Ili Region, China In seasonally frozen regions, landslides induced by snowmelt have increasingly become a prevalent disaster phenomenon. However, the specific effects of snowmelt on landslide dynamics remain not well understood. This paper selects the Zeketai River Basin in the Tian Shan as study area, aiming to explore the deformation processes and failure mechanisms of snowmelt-induced landslides. A total of 242 loess landslides were identified in the Zeketai River Basin of the Ili Region, China. 61 % of landslides are scattered across northward-facing slopes, and 70 % of the recorded landslide events (40 occurrences) transpired during spring between 1990 and 2010. The deformation and failure of these loess slopes generally manifest in late autumn (October to December) and early spring (February to April). During the snowmelt season, surface deformation exhibits a stepwise increase at a rate of approximately 120 mm/yr. Snow accumulation and melting processes are identified as the paramount driving factors of landslide dynamics. Daily and monthly surface displacements demonstrate moderate and strong positive correlations with atmospheric temperature in early spring (r = 0.72 and 0.69, respectively) and late autumn (r = 0.47 and 0.64, respectively). Furthermore, monthly snow depth shows strong negative correlations with monthly surface displacements and atmospheric temperature in early spring (r = -0.85 and −0.82, respectively) and late autumn (r = -0.7 and −0.86, respectively). Both temperature-dependent snow accumulation and melt processes, in conjunction with accompanying freeze-thaw cycles, potentially exert a combined influence on the types and mechanisms of landslides throughout different seasons. Future investigations will emphasize near-surface and subsurface thermo-hydro-related measurements and experiments to elucidate the intricate interaction mechanisms of these landslides. Climate warming is accelerating snowmelt in seasonally frozen regions, which can increase the occurrence of snowmelt-driven landslides. The loess landslides show significant season distribution and aspect differentiation in seasonally frozen regions. Snow accumulation and melting processes are the most important driving factor of landslide dynamics, providing feedback of near-surface soil hydrothermal response on landslide mechanism. Both temperature-dependent snow accumulation and melt processes, and the accompanying freeze-thaw cycles, potentially have a combined influence on the types and mechanisms of landslides across different seasons • The distribution of loess landslides is marked by strong seasonality and aspect dependence. • Snowmelt processes are key factors governing landslide dynamics. • Snow processes and freeze-thaw cycles jointly affect landslide types and mechanisms.