Analysis of hydrological response in high-hazard and semi-arid catchments of southern Calabria, Italy: Historical extreme floods and current forest fires-related events

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Study Region: The research focuses on the semi-arid Mediterranean environment, specifically on southern Calabria (Italy), an area highly prone to hydrogeological hazards due to the combined influence of natural and anthropogenic factors. Here, the Aspromonte massif is subject to multi-hazard risk: it is among the most severely affected by the large-scale, high-intensity wildfires that occurred in August 2021 and is regularly exposed to intense rainfall events that can generate severe floods. Study Focus: This study quantifies the hydrological effects of forest fires at the watershed scale in scenarios of frequent and extreme precipitation, including historically severe events. A past extreme flood was reconstructed to calibrate and validate a hydrological model capable of simulating pre- and post-fire conditions. The model was then applied to evaluate changes in peak flow rates New Hydrological Insights for the Region: Results show that, contrary to expectations, rainfall events with shorter return periods cause the greatest percentage increases in flow rate, demonstrating that forest protective action tends to decrease in conjunction with an increase in return period. The results contribute to increasing knowledge on wildfire impacts, highlighting the effectiveness of forests in reducing peak flood rates, especially during frequent rainfall events.