Improvement of landslide hazard assessments for regulatory zoning in France: STATE–OF–THE-ART perspectives and considerations

TLDR: Through this synthesis carried out as part of the regulatory mapping of landslide hazards and risks in France, a state-of-the-art spatial assessment of current landslide hazards is performed and the new tools and databases to support this type of analysis are described.

Abstract: In France, in the context of regulatory mapping (PPRNs –Prevention Plans of Natural Risk based on French regulatory rules), landslide hazard assessment follows an empirical approach and uses basic available data. Therefore, the results are closely linked to the quality of the expertise and divergent opinions may arise in some specific cases. In recent years, numerical approaches using GIS, the availability of new databases, the development of new acquisition tools in the field and web visualization services have improved the knowledge of phenomena and different landslide-prone areas. Numerical approaches using GIS, that allow the transparency and traceability of results, have various levels of complexity and require different quantities of input data. However, they are often neglected by experts and new data and tools are not currently used to develop regulatory mapping documents. Numerous scientific examples show that these numerical approaches, web services and new tools can be a significant help in improving knowledge and provide a credible alternative to the expert approach, even in a regulatory context such as a PPRN. Thus, through this synthesis carried out as part of the regulatory mapping of landslide hazards and risks in France, a state-of-the-art spatial assessment of current landslide hazards is performed. The new tools and newly available databases to support this type of analysis are then described. Finally, the perspectives and limitations of alternative approaches and new tools and data are discussed, leading to some considerations for the improvement of the current method of producing landslide hazard maps for PPRNs in France.