Meteorological conditions of the mudflow origin in the northern part of the French Alps

Abstract

A mudflow phenomena are at the top of the list of dangerous natural hazards in the mountains areas all over the world. Among factors resulting in a mudflow phenomena triggering, meteorological conditions are considered to be the most relevant. The general objective of this study was to identify meteorological parameters controlling the triggering of mudflow phenomena in one part of the French Alps over the last 40 years. Major factors are quite well explored at the global scale or contrariwise in very precise territory in particular catchment areas. However, for now we have a poor knowledge of those factors at the scale of a medium-sized region (including catchments with different geomorphic characteristics over several km²) especially in the French Alps. In addition, in this region only a few studies focused on relationships with climate. To understand mudflow phenomena activity and their link with meteorological parameters in the north region of the French Alps, we used a multivariate statistical approach. Regional meteorological parameters (such as mean monthly temperature and precipitation) were first computed from a Principal Component Analysis of observed meteorological data from four weather stations. A binomial monthly logistic regression probability model was then fitted between the main principal components and mudflow phenomena data base composed of 298 debris flow events triggered between 1971 and 2008. Results revealed that the most successful model including two meteorological predictors (minimal monthly temperature and the number of rainy days between May and September) correctly explains more than 60% of the mudflow phenomena events.