20 April 2023
The 26 November 2022 Casamicciola landslide on the island of Ischia in Italy
On 26 Novmeber 2022, a substantial debris flow, now termed the Casamicciola landslide, was triggered by heavy rainfall on the island of Ischia in Italy. This landslide, which killed 12 people and injured several more, has been described in an initial but rigorous analysis (Romeo et al. 2023) published in the journal Landslides.
The analysis shows that the landslide had a volume of about 40,000 cubic metres, which is very large for a landslide through an urban area. There is excellent data on the landslide, including field mapping, remotely sensed data, high quality rainfall records from nearby and a seismic record that has captured the landslide movement. The authors have analysed 16 years of rainfall records, from 2006 to 2022. The rainfall event that triggered the landslide, was 176.8 mm in 24 hours, the highest total in the record. The second highest value, 111 mm in 24 hours in 2009, also triggered extensive landslides on Ischia.
There is a very interesting drone video on Youtube that shows the track of the landslide:-
This video includes this still, which captures the track of the landslide through the upper part of the town:-
The authors conclude that the failure occurred in saturated debris high on the slope, with contributions from rockfalls and smaller debris flows along the track, The landslide turned into a classic channelised debris flow. Unfortunately deposition did not start until Casamicciola had been reached, meaning that the buildings took the full force of the flow. The peak velocity was in the range of 20 metres per second.
The timing of the landslide, which was one of several that occurred that day, may well have played a role in the loss of life. The landslide was triggered at about 5 am, when most people would have been asleep. Given the highly destructive nature of the landslide, there was little chance of escape.
Romeo, S., D’Angiò, D., Fraccica, A. et al. 2023. Investigation and preliminary assessment of the Casamicciola landslide in the island of Ischia (Italy) on November 26, 2022. Landslides https://doi.org/10.1007/s10346-023-02064-0