25 November 2019
Savona: a landslide-induced bridge collapse in Italy
Over the weekend extremely heavy rainfall affected a wide swathe of Europe, most notably in France and Italy. The Italian region of Liguria has suffered from multiple landslides, the most dramatic of which occurred on an elevated section of the A6 motorway on the road between Savona and Turin. There are severe rainfall alerts in Emilia Romagna (red); in Abruzzo, Calabria, Piedmont, Veneto, Marche, Lombardy and Puglia (orange); and in Val d’Aosta, Trentino, Alto Adige, Campania, Molise, Basilicata, Umbria, Sicily and Sardinia (yellow).
The event near to Savona was serious – it was fortunate that there was no loss of life given the impact:-
On first inspection this appears to be a slip in soil and regolith in a steep topographic depression or bowl. The released debris appears to have transitioned to become a channelised debris flow that has exceeded the capacity of the channel below the road.
The Savona landslide occurred close to Madonna del Monte at 44.295, 8.434. The topographic depression from which the landslide originated can be clearly seen:-
In essence this event will be down to inappropriate design of the channel below the road. It highlights the difficulty of designing structures that are able to handle the very short lived, high discharge events that occur when chanellised debris flows evolve from slope failures. As usual, I highlight the video from the 2008 Lantau events in Hong Kong to illustrate the dramatic and devastating effects of these landslides.