Evaluating the terrain susceptibility to mass movements

The variability of landslide phenomena in terms of types, velocity and size, makes it difficult to establish a unique methodology for the definition of landslide susceptibility, with different approaches proposed in the literature for the prediction of landslide occurrence. In addition, the extent of the study area and the characteristics of the available data may influence the selection of the susceptibility models. For these reasons, landslide susceptibility studies described in the literature use different modelling approaches adopting a variety of mapping units and thematic information. In this chapter, we first use a database of 565 articles from a recent systematic review of the literature to illustrate and describe a synthesis of relevant information on landslide susceptibility modelling and terrain zonation. We then present examples of susceptibility zonations prepared at four different scales: (i) continental (Europe), (ii) national (Italy), (iii) sub-national (Umbria Region, Italy), and (iv) catchment scale (Collazzone area, Italy), using different data types and resolutions, different mapping units, and various statistically-based modelling approaches. We use these four examples to provide our reflections on the proprieties of the geo-environmental data, and the main characteristics of the modelling approaches at different scales. We conclude with a few steps that could become a starting point for the discussion and definition of a standard for statistically-based landslide susceptibility methods and zonation.