The granulometry analysis identified that the debris flows were from granular type. First, the analysis of the dangerousness of the sources areas indicates that the central corridor has the higher probability of debris flows trigger. A short chapter will introduce the influence of climate change on this phenomenon.įor the specific analysis, the main purposes were to characterize the dangerousness of the sources areas, to know the type of debris flows, to estimate their sizes and to perform simulations of spread within the watershed. The frequency analysis of the watershed permit to show the importance of seasonality on the probability of occurrence of debris flows. It was possible to detect sectors that are clearly more dangerous than others. The conclusions were that the watershed is composed by two types of dynamic (high frequency and low to medium intensity or low frequency and exceptional intensity) and that the role of the deposition area (accumulation – remobilisation) is important. This approach has allowed to identify signs of previous torrential activities and thus to make some assumptions on the dynamics of the torrent. Regarding to the general analysis of the watershed, the two main goals were to create a map of phenomena and makes hypotheses on the dynamic of the watershed. An analysis of the influence of the permafrost as an aggravating factor triggering debris flows (secondary purpose). A diagnosis of debris flow hazard answering the questions when? how far? which intensity? and 4. A specific analysis of the watershed that responds to the questions why? how? and How much ? 3. A general analysis of the watershed that responds to the questions where? and what? 2. The methodology has been divided into four parts which are: 1.

The village of Versegères is on the fan, which is partly in danger. The aim of this work is to diagnose the main hazard for debris flows in the North watershed of Mt-Rogneux which is located in the Val de Bagnes in Valais / Switzerland.

Nord torrent