Abrupt drought-to-flood transitions in Australia

This study examines historical abrupt drought-to-flood transition (ADFT) events (Figure 1) across Australia using the Standardized Precipitation and Evapotranspiration Index (SPEI) at 1-, 3-and 6month scales, representing short-, mid-, and long-term transitions.On average, more than 18 ADFT events occurred per location during 1965-2024, with northern and southwestern regions emerging as hotspots, each experiencing more than 20 events.These events typically lasted about six months while can persist up to nine months.The intensity of ADFT events generally falls within the range of 2.6-3.2, as measured by the cumulative absolute SPEI over the drought and ensuing wet phases, with similar intensity for drought and subsequent wet phases.We detected statistically significant increasing trends in the frequency and intensity of ADFT events in short-term transitions.Although event durations have not lengthened, drought phases have intensified more than the wet phase, indicating more polarised hydroclimatic extremes.These findings highlight the need to account for compound climate risks in national and regional strategies, including water security, agricultural adaptation, and resilient infrastructure planning, to better navigate Australia's evolving climate reality.