Intensified floods after mega forest fires in southeast Australia

Forest fires are commonly expected to exacerbate local flood hazards. Yet, it's not well-established if such an effect is evident across broader geographic regions concurrently, particularly when considering the compounded influences of forest fires and climate variability on floods. Here, we show that recent 2019–2020 mega forest fires in southeast Australia, characterized by unprecedented burned areas, have significantly increased the flood peak discharges in the ensuing two years. The impact varied regionally, being more pronounced in areas with winter-dominated and uniform rainfall patterns, while it was insignificant in regions with summer-dominated rainfall. This regional divergence in fire impacts can be attributed to the differences in burned areas and dominant flood generating mechanisms. Given the increasing influence of climate change on fire activities, people living in these fire-prone regions might face escalating risks of cascading flood hazards following fires in the future.