Analyse d'une lave torrentielle dans le torrent de Faucon (bassin de Barcelonnette, Alpes-de-Haute-Provence). Détermination des zones de déclenchement et de contribution / Study of a debris flow event in the Faucon stream (Barcelonnette basin, Alpes-de-Haute-Provence). Determination of triggering areas and contribution areas

摘要

Abstract A geomorphic study was carried out for the first time on the Faucon torrent (Barcelonnette basin, Alpes-de-Haute-Provence), where a debris flow occurred on August 19th 1996. This flow was triggered by a severe thunderstorm in the upper part of the catchment. The rupturing of a natural dam in the stream channel caused the debris-flow. Grain-size distribution and pétrographie analysis of the debris-flow deposit bring out the granular character of the flow during the first hectometre, and its cohesive character beyond that point and as far as the debris fan. Geomorphic observations and laboratory tests show the existence of two source areas: a triggering area and several contributing areas. These contributing areas seem to have supplied the bulk of the flow material.