Exploring drought-to-flood interactions and dynamics: A global case review

This study synthesizes the current understanding of the hydrological, impact, and adaptation processes underlying drought-to-flood events (i.e., consecutive drought and flood events), and how they interact. Based on an analysis of literature and a global assessment of historic cases, we show how drought can affect flood risk and assess under which circumstances drought-to-flood interactions can lead to increased or decreased risk. We make a distinction between hydrological, socio-economic and adaptation processes. Hydrological processes include storage and runoff processes, which both seem to mostly play a role when the drought is a multiyear event and when the flood occurs during the drought. However, which process is dominant when and where, and how this is influenced by human intervention needs further research. Processes related to socio-economic impacts have been studied less than hydrological processes, but in general, changes in vulnerability seem to play an important role in increasing or decreasing drought-to-flood impacts. Additionally, there is evidence of increased water quality problems due to drought-to-flood events, when compared to drought or flood events by themselves. Adaptation affects both hydrological (e.g., through groundwater extraction) or socio-economic (e.g., influencing vulnerability) processes. There are many examples of adaptation, but there is limited evidence of when and where certain processes occur and why. Overall, research on drought-to-flood events is scarce. To increase our understanding of drought-to-flood events we need more comprehensive studies on the underlying hydrological, socio-economic, and adaptation processes and their interactions, as well as the circumstances that lead to the dominance of certain processes.