Exploring the hydrodynamic response of a highly perturbed river due to volcanic eruptions: the Blanco River, Chait?n (Chile)

This work explored the hydrodynamic response of the Blanco River to three-phase flows (water, sediment, and wood), in a context of volcanic disturbance. The scarce hydrological information makes the use of traditional methods difficult, so an alternative methodological approach was defined to determine the flood hazard through numerical modelling (Iber) and scenario design. The results showed that the discharge required to flood the town varied between 850 and 950 m3 /s for single-phase flows (water only), while for three-phase flows the discharge was much lower (between 700 and 800 m3 /s). In addition, significant differences in flooded areas were observed between scenarios with different roughness and proportion of sediment and wood in the flow. The results show the great complexity and sensitivity of the Rio Blanco River system.