Prediction and forecasting of mass-movements

In the attempt of mitigating landslide risks, the capability of quantitatively assessing hazard, that is the probability of occurrence of a possibly damaging event in time and space, is fundamental. In this chapter, we will briefly review the main operational methods for the prediction and the forecasting of the time of occurrence of mass movements and present some relevant examples concerning different landslide typologies and hazard settings. We differentiate between slope scale and basin scale approaches, and between process-based and empirically-based methods. In this framework, we distinguish three main approaches in the way the prediction is made: methods to predict failure based on slope displacement monitoring, methods based on triggering monitoring and methods based on numerical modelling. Furthermore, we hint that prediction may concern different physical variables, such as failure time, factor of safety estimation, thresholding of a signal or of a given initiation process. Although we will mainly focus on the prediction of failure time, alternative methods will be discussed also for cases where such estimation is difficult or impossible. This chapter will not treat the prediction of the failure location that is left to a specific section.