Monitoraggio di un pendio naturale in depositi piroclastici sciolti

"Hilly areas in Northern Campania are characterised by steep slopes covered by loose volcanic ashes covering a calcareous bedrock. Slope inclination is often larger than the internal friction angle of ash (around 38°), thus slope stability is assured by the contribution of apparent cohesion due to soil suction. Shallow landslides are frequently triggered during intense and persistent rainfall events, due to soil saturation and suction decrease. Triggered landslides often turn into debris flows, which cause huge damages and, in some cases, even casualties. Field hydrological monitoring is an useful tool to develop reliable models of slope response to rainfall, and hence to define the triggering conditions.. An automatic monitoring station has been recently installed in Cervinara, 30 Km East of Naples, where a catastrophic landslide occurred in December 1999. The station consists of a tipping bucket rain gauge, with a sensitivity to rainfall height of 0.2 mm; eight jet fill tensiometers, for the measurement of soil suction at different depths from 0.50 m to 1.70 m below the ground surface; seven TDR probes of various lengths, connected through a multiplexer to a reflectometer, for the measurement of volumetric water content profile from ground surface up to a depth of 1.60 m. All sensors are connected to a datalogger for the automatic data acquisition at hourly frequency. Such data are stored into a magnetic memory which is periodically downloaded into a PC. The entire station is operated by a lithium battery connected to a solar panel. Preliminary data confirm the usefulness of simultaneous monitoring, at high temporal resolution, of rainfall height, soil suction and soil water content for a better understanding of slope infiltration processes.