Observations on 1998 Campanian debris avalanches and debris flows

The debris avalanches and debris flows of the western Campanian relief are among the most hazardous landslides in the Italian Apennines. On 5/6 May 1998 over twenty flows hit the piedmont towns of Sarno, Quindici, Siano, Bracigliano, 30 Km to the east of Naples. Triggered by intense rainfalls, high velocity flows destroyed a large number of houses killing 161 people. The typical geological environment of such debris flows is characterized by the presence of limestone bedrock mantled by pyroclastic deposits originating from the eruptions of Campi Flegrei and Somma-Vesuvius volcanoes. The surveys performed pointed out that the landslides initiated in the upper part of the slope and of the main and secondary gullies; the largest number of cases indicate that the natural or artificial scarps have an important role in triggering mechanisms. The presence of filling material in the gullies is also crucial in developing the high-velocity flows