A global stocktake of research on the interactions between flood and drought risk

Floods and droughts are opposite extremes on the hydrological cycle, yet their risks are highly interconnected. Their interactions emerge through temporal and spatial overlaps, system dependencies, and dynamics across not only hazard but also vulnerability, exposure, and response determinants. However, existing research on flood–drought interactions remains scattered. Existing syntheses focus on hazard dynamics, providing limited insight into how they translate into societal risk. Here, we address this gap by systematically reviewing literature addressing flood-drought interactions beyond hazard determinants.

Using a Web of Science search, we retrieved 1,909 papers using flood, drought, interactions, and dynamics-related keywords. Following a preliminary round of manual coding, we applied a machine learning classifier to remove 1,115 unrelated documents, achieving an accuracy of 78%. We then conducted two levels of full-text screening on the potentially relevant articles (n=794) to identify (i) the considered risk determinants, and (ii) their level of risk assessment: single-risk, multilayer single-risk (i.e. risk of multiple hazards without interactions), or multi-risk.

Preliminary findings show that only 43 studies could be classified as multi-risk and explicitly focus on flood-drought interactions beyond hazard determinants. In fact, most research, including studies labeled as “multi-risk”, treats floods and droughts as separate phenomena and provides little insight into their interactions. For these 43 studies, we conducted a full-text analysis to capture information on the types of dynamics considered, the impacted sectors, additional hazards considered, the applied methods, and the spatial and temporal scales of the analyses. In general, most studies focused on response-related (72%) and temporal dynamics (72%), whereas spatial dynamics and interactions across sectors remain understudied (26% and 42%, respectively).

In the next steps, we will use insights from the reviewed evidence to assess these dynamics across past flood-drought events and show how comprehensively studies address the full risk framework. The methodological approaches used to explore these interactions will be synthesised to identify how they are studied, best practices, and remaining gaps. Finally, this review will contribute to a comprehensive understanding of compound flood–drought events and their systemic risks by revealing the diversity of their dynamics and non-linear relationships, while also providing a structured basis to guide future research efforts toward the most critical knowledge gaps and methodological priorities needed to advance multi-risk assessments.