Amplified Drought and Flood Risk Under Future Socioeconomic and Climatic Change

Abstract

The economic stress and damage from natural hazards are escalating at an alarming rate, calling for anticipatory risk management. Yet few studies have projected flood and drought risk, owing to large uncertainties, strong non-linearities, and complex spatial-temporal dynamics. Here, we develop an integrative global risk analysis framework encapsulating future changes in flood and drought hazards as well as associated exposure and vulnerability dimensions. Flood characteristics are quantified by fitting a generalized extreme value distribution (GEV) to the annual flow maxima time series, while drought properties are characterized by the standardized precipitation evapotranspiration index (SPEI) and the standardized precipitation index (SPI). The drivers of drought and flood risk changes at the global and regional scales are explored, and the wide cascade of uncertainties in the risk assessment is decomposed. We find a substantial increase in both flood and drought risk towards the end of the century over most of the globe, driven by compounding changes in exposure, vulnerability, and hazard. A shift from a fossil-fueled development to a sustainable one decreases the global area facing a risk doubling from 61% to 33% for flood and from 41% to 23% for drought. South America and Africa are identified as hotspot regions where a concomitant, large increase in both flood and drought risk are projected. The hazard quantification method is ubiquitously the dominant uncertainty source for drought risk changes, while the contribution of uncertainty sources for flood risk changes is highly variable in space.