Influence of the Antecedent Long-term Precipitations on the Initial Conditions in a Sloping Pyroclastic Deposit

The hydrological response of a shallow sloping deposit in unsaturated pyroclastic soils is being monitored since 2002. The area is located in Cervinara, Campania Region (Southern Italy), where a catastrophic flowslide occurred on December 16th, 1999, as a consequence of a 2-day cumulative rainfall of 320 mm causing heavy damage and five deaths. The installed devices provide information about rainfall height, soil suction and, recently, also about volumetric water content at several locations and depths along the slope. The huge number and high quality of data allowed to develop a consistent model about the hydrological slope response and particularly to correlate the antecedent long-term precipitations with the soil matric suction at the beginning of a potential triggering rainfall, focusing on the hydrological conditions that establish in the different seasons. In particular, this can help in assessing the likely initial suction values at the time of a potential triggering rainstorm.