Debris flow hazard assessment and mapping; application to a case study in the French Alps

The paper presents a methodology developed to determine the spatial "debris-flow initiation hazard". Through the field study of twelve catchments prone to debris flows in the French Alps and the laboratory analyses of many samples of debris-flow deposits and source-area materials, data on the environmental setting are provided. The potential debris-flow source-areas are localized, and their characteristics compared. Relying on this analysis, the author has selected five predisposition factors that are relevant to debris-flow initiation, which are related to slope angle, geology, mass movements, volumes and granulometric properties of superficial deposits. The data related to these factors were quantified and processed using an algorithm, and maps of the "debris-flow initiation" hazard were produced. The methodology provides a special emphasize on geotechnical data and quaternary geology. They illustrate the spatial distribution of potential events and allow identifying potential source areas and planning works in order to mitigate the risk.
QC 20181026