Investigation and preliminary assessment of the Casamicciola landslide in the island of Ischia (Italy) on November 26, 2022

On 26^th November 2022, as a consequence of heavy rainfall, diffuse landslides were triggered in the Northern sector of Ischia. The present study investigated the main features of the debris flow originated in a small catchment basin falling within the Casamicciola Terme Municipality. The process under study affected about 30 buildings causing 12 casualties and several injured, more than 200 people displaced, and severe damages to the road network, resulting one of the most destructive landslide event occurred in the island. A multidisciplinary works for preliminary assessment, including on-field investigation, data analysis, and numerical modelling, was performed taking also into account geomorphological, geological and climate evidence.

The debris flow, originated around 05:00 a.m. from the Northern slope of Mt. Epomeo, travelled about 850m before impacting a populated area, destroying buildings, and claiming many casualties. Along the pre-existing channel were observed a marked erosional behaviour with maximum removed thickness of about 5.5m while the material deposition largely occurred after the impact on buildings. The total volume mobilised by the debris flow can be estimated at approximately 40,000m³.

Considering the geological and geomorphological conditions, as well as the high vulnerability and the socio-economic importance of the area, a careful monitoring and risk management activities in the next months are necessary.