Hydrological characterisation of possible triggering scenarios in slope instability

One of the most frequent landslide triggering causes are rainfalls which can determine such variation in pore pressures to reduce the shear strength and to determine slope instabilities. To realize failure mechanisms, surveys, investigations and analysis are expensive indispensable conditions. Then hydrological models are very useful to define scenarios that could trigger landslides generally classifiable and connected to homogeneous geoenvironmental contexts. Three classes of instabilities are considered: shallow (SH), medium deep (MD) and deep (DD) landslides. The hydrological analysis has been carried out referring to geo-environmental contexts in which landslides, referable to the considered classes, are traceable. For SH the employed procedure consists of analysing the heaviest rainy events. The analysis of rainfalls cumulated at the daily scale on prolonged periods or an indirect analysis of the soil moisture content, through the AR(l) autoregressive model, are used to study MD. For the DD, temporal periods longer than one rainy season are considered. A monthly temporal scale is then adopted with reference to cumulated rainfall and to the AR(l) model. Results allow us to define possible triggering scenarios for the considered instability classes and in the ambit of the geo-environmental,contexts chosen as references. The scenarios we found may allow us to calibrate the instability mechanisms referring to simplified geotechnical schemes individuated as representative of homogeneous geo-environmental contexts.