Steep-slope monitoring in unsaturated pyroclastic soils

Based on monitoring results, the paper describes the hydrological response of a steep hillslope covered by unsaturated pyroclastic soils. The instrumented site is located just beside an area which experienced a catastrophic flowslide two years prior to the survey. Monitoring involved rainfall and matric suction measured at different locations and depths. Investigations focused on the hydrological response of the slope so as to model the effects of rainfall and then predict the onset of slope failure triggered by critical rainfall.

► Monitoring can be a useful tool to predict the hydrological response of slopes.
► The slope behaviour at a given time depends on history of both wet and dry phases.
► The effects of precipitation and evaporation on the pore pressure regime are delayed.
► Monitoring enables to extrapolate a threshold value for daily evapotranspiration.