The Rigopiano tragedy: dendrochronological analyses of the trees along the avalanche track

In the afternoon of 18 January 2017, an avalanche destroyed the luxury resort Hotel Rigopiano on the Gran Sasso d'Italia massif, in the municipality of Farindola (in the province of Pescara, in the Abruzzo region of Italy) causing the death of 29 people. The hotel walls were brought down, and the entire building was moved ten metres downhill. This is the most serious tragedy caused by an avalanche, in Italy since 1916. Apart from the avalanche, from 24 August 2016, all of central Italy was subjected to repeated earthquakes, denominated the "Seismic Sequence of Amatrice-Norcia-Visso" by the INGV (the National Institute of Geophysics and Volcanology). About four hours before the Rigopiano avalanche, there were fouraftershocks. Moreover, from 5-21 January, 2017, a powerful wave of cold weather affected a large part of Europe, including Italy, causing heavy snowfall even along the coast, but especially along the Apennines. Hence, at Rigopiano, earthquakes, low temperatures and an avalanche occurred at the same time. Today, the Rigopiano disaster is subject to legal investigations and scientific studies. The most important issue is to assess whether avalanches have come down at Rigopiano before, perhaps regularly, and with a similar force of that of 18 January. The trees brought down by the avalanche, and those in the surrounding beech woodland, were analysed dendrochronologically in order to: a) estimate the trees' ages, with a view to determining possible previous avalanches; b) assess the presence of potential injuries or traumas in the wood, caused by avalanches or debris flows, particularly along the edge of the avalanche track and in the 2017 detachment zone; c) analyse the dendrochronological series in order to identify indications of previous disturbances that may have influenced tree growth. A mean chronology was set up, spanning 99 years, from 1918 to 2016. The average age of the samples is 65.5 years, ranging from 32 to 99 years of age. The trees' germination period varies but it is concentrated in the 1930s. In addition, sensitivity, pith eccentricity, pointer and event years were recorded. During the Conference, the results will be presented and discussed.