It is widely recognised that soil slips and debris flows are triggered by short intense storms. Owing its geologic, geomorphologic and climatic settings, the Piedmont Region (NW Italy) is highly prone to the occurrence of this kind of landslides. In the last two centuries, in fact, a total of 105 severe meteoric events which triggered shallow failures occurred and, of these, 18 events took place from 1990 to 2002. A fair number of rainfall thresholds have been proposed in the literature, defined both on empirical or on physical bases. Empirical thresholds are defined collecting rainfall data for landslide meteoric events and for events without landslides, while physical thresholds are based on numerical models that consider the relation between rainfall, pore pressure and slope stability.

The main objective of this paper is the identification of the empirical triggering thresholds for the Piedmont Region. Four meteoric events were selected and analysed (November 4–5, 1994; July 7–8, 1996; April 27–30, 2000; October 13–16, 2000) because they supply a wide range of variation for both rainfall parameters (duration, intensity, cumulative rainfalls) and the number of induced landslides.