Recommended citation: Gimeno, L., Nieto, R., Stojanovic, M., Sorí, R., Pérez-Alarcón, A. (2026). Atmospheric rivers are associated with nine out of every 10 floods in major global river basins. RGS-IBG Annual International Conference 2026. London, United Kingdom, 1-3 September 2026.

Abstract

Atmospheric rivers (ARs) are increasingly recognised as a key driver of extreme precipitation. However, their global role in generating floods across major river basins remains incompletely quantified. In this study, we examine the relationship between ARs and 119 significant flood events that occurred in 50 major river basins worldwide between 1999 and 2018. Using an objective, global AR detection algorithm and a comprehensive flood database, we analyse the spatiotemporal coincidence of ARs with flood-affected areas and entire river basins. We consider both the flood periods themselves and the three days preceding flood onset, in order to capture both immediate and antecedent effects. Our results demonstrate that ARs intersected 74% of flood-affected areas and influenced up to 89% of corresponding river basins, showing that almost nine out of ten major floods worldwide are associated with AR activity. The influence of ARs extends beyond direct overlap with flooded regions, emphasising the importance of upstream precipitation and basin-scale hydrological processes in flood generation. AR-related impacts were identified across a wide range of climatic zones, including basins where AR–flood relationships have previously been poorly documented, from mid-latitude to tropical regions. In many cases, ARs acted as both immediate flood triggers and antecedent preconditioners, increasing soil moisture and lowering runoff thresholds prior to flood onset. In addition to their hydrological relevance, AR-associated floods were linked to substantial societal impacts, including fatalities and large-scale population displacement, particularly in densely populated and vulnerable river basins. Overall, our findings establish ARs as dominant and pervasive drivers of major flood events on a global scale, with important implications for flood forecasting, risk assessment and climate change adaptation strategies.