Catastrophic debris flow triggered by an extreme rainfall event in the Volcán village, January 2017. Cordillera Oriental of Argentina

Abstract. Slides, rockfalls, debris floods and debris flows are periodical events in the dry mountainous regions of Argentina, during times of torrential rainfalls. In the Grande River basin, Jujuy Province, these processes take place almost every summer. Extreme rainfall on January 10, 2017 caused the seasonal acceleration of large-scale and slow-moving landslides in the Los Filtros River basin. These slides broke down into a disaggregated mass, triggering a debris flow which transformed progressively downstream into a debris flood, producing widespread damage along a narrow valley (named Quebrada de Humahuaca), with the Volcán village withstanding the worst of the disaster. The event caused four fatalities and great economic losses, mainly destroying infrastructure and buildings. In order to document this catastrophic event and to explore its causes, a morphometric analysis of the Los Filtros river basin, tributary of the western margin of the Grande River and located on the Cordillera Oriental area, was carried out. The drainage network was derived from digital elevation models. In addition, some landslides were mapped using high-resolution satellite data acquired before and after the event. Of a total landslide area of 2.39 km², 0.60 km² was considered as active and 0.089 km² as new sliding area (from 2015 to 2017) associated to the large-scale and slow-moving landslides. The geological characteristics of the study basin are very favourable conditioning factors in landslide generation. Precambrian-age low grade metaclastics shatter in the frost climate of the higher mountains and poorly consolidated Quaternary deposits along the sides of the gully erode readily and become source material for landslide that damage or bury roads, railroads, and houses. Finally, this study aims to increase knowledge of all the above-mentioned events in order to provide several methods of analysis for landslide prevention and control.