Movements, failure and climatic control of the Veslemannen rockslide, Western Norway

Abstract On September 5, 2019, the Veslemannen unstable rock slope (54,000 m 3 ) in Romsdalen, Western Norway, failed catastrophically after 5 years of continuous monitoring. During this period, weakened while precursor movements increased progressively, particular from 2017. Measured displacement prior to failure was around 19 upper parts instability and 4–5 toe area. The pre-failure were usually associated with precipitation events, where peak velocities occurred 2–12 h maximum precipitation. This indicates that pore-water pressure sliding zones had a large influence on stability. sensitivity rainfall greatly spring autumn suggesting thermal control pressure. Transient modelling temperatures suggests near permafrost conditions, deep seasonal frost certainly present. We propose frozen surface layer prevented water percolation zone during snowmelt early summer rainfalls. A transition possible setting landslide body 2000 modelled, which may have affected Repeated rapid accelerations late summers autumns caused total 16 events red (high) hazard level evacuation zone. Threshold values for velocity used risk management when increasing or decreasing levels. inverse method initially little value. However, final phase before failure, useful forecasting time failure. Risk communication important maintaining public trust early-warning systems, especially critical is difference between issuing predicting landslide.