Geomorphological evolution of the Blanco Este River after recent eruptions of the Calbuco volcano, Chile

In this paper, we retrace the geomorphological evolution of a 6.5 km-long segment of the Blanco Este River, which drains the Calbuco volcano in southern Chile, highlighting the geomorphic signatures of the disturbances caused by the 1961 and 2015 eruptions. In particular, we track the geomorphological changes and the evolution of the geomorphological units and discuss the underlying processes. In addition, we use the NDVI (Normalize Difference Vegetation Index) to characterise the vegetation recovery at the basin and the active channel scales. The reconstruction of the geomorphological changes is performed by means of photointerpretation and super-vised classification image analysis. Moreover, we quantify braiding indices and active channel widths to char-acterise the fluvial corridor and to describe its evolution after the two eruptive events. It is found that the evolutionary trajectories of the Blanco River immediately after the eruptive events of 1961 and 2015 exhibited strong similarities. In fact, the major geomorphological adjustment of the Blanco Este River occurred during the first period of observation (19 years) after the 1961 eruption. Subsequently the river progressed gradually to-wards an advanced relaxation stage in 2014. For 53 years (between 1961 and 2014), the reduction of the active channel width was the dominant process, followed by erosion, which favoured the regeneration and consequent expansion of vegetation cover within the river corridor. The 2015 eruption reset the fluvial landform and a new cycle of sedimentation, braiding and formation of central bars began; the highly dynamic pattern is still observed today.

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This paper investigates the geomorphological evolution of a segment of the Blanco Este River in southern Chile, focusing on the disturbances caused by the eruptions in 1961 and 2015. The study reconstructs the geomorphological changes using photointerpretation and image analysis, and analyzes the evolution of geomorphological units and processes. The study also examines the vegetation recovery using the NDVI and characterizes the fluvial corridor using braiding indices and active channel widths. The findings show similar evolutionary trajectories after the 1961 and 2015 eruptions, with major adjustments occurring in the first period of observation after the 1961 eruption, followed by gradual relaxation and regeneration of vegetation cover. The 2015 eruption reset the fluvial landform and initiated a new cycle of sedimentation and braiding.