Abstract
Surface subsidence above salt mines reflects the complex interaction of elastic and viscous deformation processes in rock salt, as well as hydrogeological and structural changes within diapiric formations. This study evaluates long-term ground movements above two Polish salt diapirs: Wapno, affected by catastrophic flooding in 1977, and Kłodawa, where mining continues in selected panels. High-precision levelling records collected over several decades were analysed to determine subsidence magnitude, trough geometry and time-dependent deformation behaviour. In Wapno, suffosion and dissolution caused extensive discontinuous failures, whereas in Kłodawa, deformation remains primarily continuous and controlled by chamber convergence. By introducing and applying the concept of observational capacity, the research highlights the necessity of maintaining geodetic monitoring networks capable of capturing evolving deformation fields. The findings support the implementation of sustained levelling campaigns to ensure infrastructure safety, validate geomechanical models and enhance land-use planning in salt-mining regions.