Integrating Spatial Multi-criteria Evaluation and Expert Knowledge for Country-Scale Landslide Susceptibility Analysis: Application to France

Information on landslide susceptibility and hazard at the national scale is of fundamental importance for the design and implementation of risk management policies and the prioritarization of the allocation of resources. Lack of such information in Europe and the implementation of the European Union’s Thematic Strategy for Soil Protection (Commission of the European Communities, Thematic strategy for soil protection. COM(2006)231 final. Brussels, 2006a; Commission of the European Communities, Proposal for a Directive of the European Parliament and of the Council establishing a framework for the protection of soil and amending directive 2004/35/EC. COM(2006)232 final. Brussels, 2006b) let to an initiative of JRC (Joint Research Centre, European Commission) to setup a European Landslide Expert Group in order to identify the areas in Europe where landslides are likely to occur. In this context, this work presents the method developed for the creation of the ‘Tier 1’ landslide susceptibility map for France at a 1:1M scale, where susceptibility is defined as the spatial probability of occurrence of an event. The method is applied by differentiating three categories of landslide types, namely slides, falls and flows. More specifically, the method combines a weighting-rating procedure of both factors and classes of factors using a spatial-multi-criteria evaluation technique (SMCE) and an objective calibration of the weights based on statistics on the distribution of observed landslides per slope angle, lithology and landcover classes. The quality of the nation-scale map is evaluated with references (1) to the French landslide inventory map BDMvT, and (2) to regional or local susceptibility maps available in the literature or created for planning purposes.