A stop along the A.M.AL.PI.18 geotourist itinerary to discover large alpine landslides : the Piuro 1618 disaster

Alpine valleys have always been exploited both for their natural resources and for their strategic role as commercial pathways, but some of them had become tragically notorious even for the natural disasters that have affected their territories and the social economic life of the communities therein. To increase the awareness of natural hazards in mountain settings and to promote a risk and resilience culture, the Interreg IT-CH project A.M.AL.PI.18 will develop a geo-cultural itinerary across the Bregaglia, Valchiavenna, Moesa and Ticino Valleys, guiding the excursionists to discover some large landslides that have strongly shaped these territories. Among these, the historical catastrophic event that certainly had the strongest impact, remaining impressed on the collective imagination and artistic representations, is the Piuro landslide, that in 1618 buried an entire village causing at least 1000 losses. To reconstruct the history of that event and build up a scientifically based narrative, a multidisciplinary investigative approach is needed. Several archeological excavations have been performed revealing some parts of the ancient town and giving us some hints on the pre-event ground surface and on the geological features of the landslide body, such as the nature and size distribution of deposits. Geological and geomorphological mapping have permitted to define the detachment zone, the structural and geomechanical features of the rock mass, and the extension of the landslide deposits at the valley bottom. Two well-logs respectively 76 and 25 m deep have been performed for deciphering the thickness of the landslide deposits and the stratigraphy of the sedimentary sequence that fills the valley, also supported by gamma ray and seismic velocities inspections. Geophysical surveys (mainly by HVSR technique) have contributed to the 3D reconstruction of the valley geometry. Moreover, the implementation of numerical models to simulate the slope evolution, in terms of predisposing and triggering instability factors of the 1618 Piuro landslide, is undergoing. The route will be equipped with specific installations, and the information will be also shared by mobile applications and social networks tools. Acting in a common historical-landscape context, the cross-border geo-cultural path, which will hinge on the new alpine large landslide center (Centro Transfrontaliero Grandi Frane Alpine) planned in Chiavenna within the project, will contribute to enhance the perception of beauty and the awareness of geo-hazard towards the risk mitigation within these territories in constant evolution. The present work was co-funded through the EU, Regional Development European Fund, by Italian State, Helvetic Confederation and Cantons under the Interreg V-A IT-CH 2014-2020 Cooperation Program. Italy-Switzerland Cooperation Program, A.M.AL.PI.2018 “Alpi in Movimento, Movimento nelle Alpi. Piuro 1618-2018, ID 594274 – Axis 2 “Cultural and natural enhancement”.