Debris flows on 9 and 14 August 2015 in the Southwestern Alps. 

From 9th to 14th August 2015 the Southwestern Alps have been affected by heavy rainstorms, which caused debris flows within small basins already affected by such processes. On August 9th, a series of rain-cells in rapid succession went to crossing a narrow mountainous alpine belt oriented southwest/northeast, affecting at first the Clarée valley in French territory, then the Higher Susa valley and the Cenischia valley. On 14th August other downpours still occurred marginally affecting the Clarée valley, then the opposite slopes of the Col Clapier at the Mont Cenis pass, the Cenischia valley and the left slope of the Arc stream, in France. With the aim to check the effects on land of the rain showers we surveyed locally the geological and morphological set up conditioning the debris flow’s occurrence; thus the source areas, triggering conditions, debris volumes involved and types of processes have been assessed through direct onsite recognitions. The data collected improve the knowledge yet acquired and allow to better understand the triggering and behavior of the mass transport processes.

Keywords: Debris flow, southwestern Alps, geology.