Unravelling Multi-Hazard Events in a Coastal Catchment: Implications of Climate Change for Central Chile

Climate change is severely altering rainfall patterns and increasing the frequency and severity of wildfires, resulting in significant changes in the physical characteristics of catchments. These changes, particularly in hydrological and stability characteristics, contribute to an increased occurrence of hillslope hydrological hazards, including landslides, debris flows, flash floods, and hillslope erosion. The dynamic interplay between climate-induced changes and catchment characteristics drives complex multi-hazard interactions—such as cascading, compounding, conditional, and concurrent events— that amplify the magnitude and impact of these hazards on communities and infrastructure.

Central Chile is particularly vulnerable to climate change, especially to El Niño-Southern Oscillation (ENSO) variability, which affects rainfall patterns, and to prolonged droughts, which climate projections indicate will increase wildfires. This study examines the Marga-Marga catchment, a highly urbanised coastal area in central Chile, which has experienced large-scale wildfires in recent years that have removed significant vegetation cover, leaving hillslopes more prone to hillslope hydrological hazards during rainfall events.

This study uses advanced multi-hazard modelling and climate scenario analysis to investigate the response of the Marga-Marga catchment to evolving climate conditions. By integrating high-resolution geospatial data and physically-based modelling, and scenario simulations, it explores how climate change-driven alterations in catchment characteristics intensify multi-hazard dynamics and interactions. Preliminary results show that key catchment characteristics - such as soil infiltration capacity, moisture content and slope stability are significantly affected by vegetation loss and soil degradation due to wildfires and urbanisation. These characteristics respond differently to rainfall, thereby increasing the susceptibility of the catchment to hillslope hydrological hazards interactions.

The results provide valuable insights into the mechanisms driving multi-hazard interactions and illustrate how these processes amplify risks to natural and urban systems. This research highlights the urgent need for adaptive urban planning and disaster risk reduction strategies to mitigate these impacts. By addressing critical gaps in the understanding of multi-hazard dynamics under climate change, this study provides actionable recommendations for improving resilience in Mediterranean coastal catchments.