Landslide Susceptibility Mapping at National Scale: The Italian Case Study

Landslide susceptibility maps are key tools for land use planning, management and risk mitigation. The Landslide susceptibility map of Italy, scale 1:1,000,000 is being realized by using the Italian Landslide Inventory – Progetto IFFI and a set of contributing factors, such as surface parameters derived from 20 to20 m DEM, lithological map obtained from the geological map of Italy 1:500,000, and land use map (Corine Land Cover 2000). These databases have been subjected to a quality analysis with the aim of assessing the completeness, homogeneity and reliability of data, and identifying representative areas which may be used as training and test areas for the implementation of landslide susceptibility models. In order to implement the models, physiographic domains of homogeneous geology and geomorphology have been identified, and landslides have been divided into three main classes in order to take into account specific sets of conditioning factors: (a) rockfalls and rock-avalanches; (b) slow mass movements, (c) debris flows. The modelling tests performed with different techniques (Discriminant Anaysis, Logistic Regression, Bayesian Tree Random Forest) provided good results, once applied with the appropriate selection of training and validations sets and with a significant number of statistical units.