Frequent rock slope failures and rock subsidence from permafrost-affected mountains pose an increasing hazard on high mountain infrastructure and individuals exemplified by hundreds of recent rockfalls and frequent rock subsidence problems affecting cable cars and alpine huts. This creates a major challenge at the interface of geomechanical and snow research and infrastructure engineering. This project combines cutting edge competences on rock-ice mechanics in thawing permafrost rocks (TUM Landslides), relative gravimetrical techniques to decipher critical hydrostatic pressure levels (TUM Physical Geodesy) and thermal permafrost rock models including snow infiltration (SLF, CH). Sudden changes of hydrostatic pressure are a poorly understood key control of permafrost rock slope failure. Snow and ice provide high infiltration, permafrost seals fractured rock causing hydrostatic pressure peaks. Combining electrical resistivity tomography (ERT) monitoring of permafrost extend inside rock faces and relative gravimetrical monitoring (RGM), we have developed the 1st method capable of spatially measuring perched groundwater causing critical hydrostatic pressure levels in a 3-year benchmark experiment at the Zugspitze. In this proposal, we combine (i) snow and water infiltration modelling, (ii) the development of a sound benchmark method to derive hydrostatic pressure from RGM and ERT and (iii) mechanical modelling of the impact of sudden hydrostatic pressure variations on rock instability at two fully-equipped permafrost investigation sites (Zugspitze, D and Gemsstock, CH).