Assessment of geomorphological, hydrometeorological and geological trigger conditions of debris flows in northern Patagonia Andes

Abstract

Debris flows represent significant threats in the Northern Andes of Patagonia (NAP). On May 1, 2019, during the winter season, an extreme hydrometeorological event of 122 mm accumulated in 24 h triggered debris flows in the Chaiguaco sector (42.1°S/72.4°W), cutting off different sections of the interregional highway with their deposits, leading southern Patagonia with no connection to the rest of Chile. The Chaiguaco debris flow represents the largest event generated at 1,240 m a.s.l. in an area heavily affected by faults. In this study, we conducted a comprehensive assessment of the factors influencing the generation of debris flows in the area, integrating field and laboratory analyses based on this representative event. The study explores three main aspects. The study explores a comprehensive interconnection of geomorphological, hydrometeorological, geotechnical, lithological, structural and mineralogical analysis, emphasizing the initiation of mass movements that can evolve into debris flows. We conclude that the Chaiguaco event represents a typical case of the NAP where an extreme hydrometeorological event in an environment where multiple factors interact triggers debris flows. We suggest addressing future studies from an interdisciplinary perspective, which can serve as baseline inputs for decision-making entities within the framework of the civil protection system of the NAP.