Tree rings indicate hazards related to a waterside landslide in the Northern Apennines, Italy – A preliminary step towards forecasting landslides and related tsunami

We analysed landslide activity on a slope above the Lago di Trebecco reservoir (Northern Apennines, Italy) and indicated a hazard of future destructive landslide reactivation. We used dendrochronology in a variant of eccentric growth analysis to indicate the hazard of sudden slope failure, which could reach the water reservoir and form a tsunami. We use the previous pattern of eccentric growth of trees, found in the case of two landslides reactivated in a landslide catastrophe in Poland in 2010. Before the disaster, trees formed a specific eccentric growth pattern which preceded and can predict landslide catastrophe (sudden slope failure). This pattern was compared to trees growing on the Lago di Trebecco landslide to estimate the hazard of future destructive landslide occurrence. Trees sampled on the landslide above the Lago di Trebecco have recorded a gradual increase in activity over the last few decades. This means the landslide has become increasingly active. On the other hand, in the last two years, a significant decrease in landslide activity has been recorded on the Lago di Trebecco landslide; activity of landslides located in Poland increased significantly two years before the landslide catastrophe in 2010. This means no dendrochronological records indicate that the Lago di Trebecco landslide will be triggered in a short time, but the landslide should be monitored because of the increasing activity over the past decades. Dendrochronology can be a useful indicator for the hazard of a landslide catastrophe (sudden slope failure), which can enter lakes and induce tsunamis.