Haile, G. G., Islam, S., Tang, Q., & Wood, D. (2026). Unravelling global patterns of drought-flood alternations. Journal of Hydrology, 135718.

Abstract

Droughts and floods are among the most damaging climate extremes, yet their abrupt alternations, rapid shifts from one to the other, remain poorly understood on a global scale. This study presents a comprehensive spatiotemporal analysis of abrupt drought-to-flood (DTF) and flood-to-drought (FTD) alternations worldwide from 1981 to 2023. Results show that these events are frequent, spatially widespread, and often occur concurrently with increasing levels of abrupt transitions in both directions. Regions with increasing FTD and DTF trends include the Yangtze Basin, Eastern India, Pakistan, and Southeast Africa, while California, Southern Africa, and Emilia-Romagna show declining trends, with California exhibiting a statistically significant decrease in FTD events (p < 0.1). In Southern Africa, the FTD coverage peaked at 5.5% in 1990, then declined to 4.6% in 2016. Emilia-Romagna (Italy) demonstrated greater temporal variability, with FTD areas rising from 7% in 1982 to 11% in 2005, before falling to 9% by 2022. DTF events were most frequent in Southern Africa (7.06 DTFs in 43 years) and Emilia-Romagna (7.13), while FTD events were highest in the Mississippi (8.73) and Yangtze (6.86) basins. Conversely, Eastern India and California exhibited consistently low frequencies of both DTF and FTD. These spatial disparities underscore the complex and region-specific dynamics of hydroclimatic extremes. Improved understanding of drought-flood alternations is essential for strengthening early warning systems, risk management, and adaptation strategies in vulnerable regions worldwide.