Cascading geomorphic hazards triggered by fluvial floods in an anthropogenically-impacted beach

Beach erosion represents a major hazard to coastal regions worldwide, yet the role of fluvial floods remains an understudied component of beach dynamics. Accounting for fluvial flooding is essential, as its neglect introduces biases and uncertainties in coastal zone management, particularly in complex, anthropized environments. We propose an integrated approach to investigate the relationship between fluvial floods and beach erosion along an anthropogenically impacted beach of the Atacama Desert in northern Chile. Bathymetric changes induced by flood events (2015 and 2017) were delimited on the beach formed by mining-related tailings accumulation (1938–1975). Interannual variations in beach erosion rates were quantified using satellite imagery by comparing post-flood conditions with the pre-flood period. In addition, a numerical model was implemented to assess the spatial variability of wave-driven erosion and to identify the main factors controlling the post-flood increase in erosion. Simulated erosion rates based on post-flood bathymetry are consistent with shoreline change rates derived from satellite data. We conclude that anthropogenic beach modification, combined with flood-triggered processes, generated a positive feedback cascade that led to a prolonged erosive phase lasting several years after the flood events.