Analytical estimation of hazard and risk in landslide prone areas

The evaluation of hazard, considered as the probability of landslide occurring within a given time, can be performed by means of several methods. For specific sites where the value of the element at risk is very high the use of probabilistic methods of analysis appears to be more and more necessary. The geometry of the slope, the piezometric pressures, and the mechanical properties of soils involved must be known to evaluate stability. For applying probabilistic methods the variability of all previously listed parameters must be known. In particular in defining the soil model a sufficient number of data must be collected to describe mechanical soil variability. Analogously the water regime must be recorded and studied to define the variability of piezometric pressures. The first variability (of soil properties) is independent of time,the second (of water regime) is strictly dependent on time. Further triggering events to be considered are: Man made actions, and earthquakes. The paper highlights some of the aspects previously listed and specifically those concerning soil resistance, permeability and water pressures, considering the variability models to be used for a soil mass, and subsequently, probabilistic approaches.