Recent Changes in the Magnitude of Flood-Generation Mechanisms across Africa: Relative Contributions of Climate Change and Decadal Variability

African countries are highly vulnerable to floods, with several studies reporting an increase in mortality rate and exposure in recent decades. Therefore, to improve flood forecasting and associated resilience to such natural hazards, a better understanding of the dominant flood-generating mechanisms and their evolution across Africa is of paramount importance. According to a recent study, excess rains on saturated soils in western Africa, and long rains for catchments in northern and southern Africa, are the two dominant mechanisms, contributing to more than 75% of all flood events. While the dominance of flood-generating mechanisms was not reported to change significantly in recent decades, the magnitude of those events may have changed in response to changing rainfall patterns (wetter or drier average conditions) across Africa. Here, we first estimate how much the magnitude of events with excess rainfall on saturated soils and long rains have changed over the last 65 years, before examining the statistical relationship between these changes, globally warming temperatures, and “natural” modes of decadal climate variability (e.g., Atlantic Multidecadal Variability [AMV], Pacific Decadal Variability [PDV]). To do so, we use a non-linear extreme value modelling approach with multiple covariates, applied to multiple observational datasets (e.g., ERA5, REGEN) and large ensembles from the Sixth Phase of the Coupled Model Intercomparison Project (CMIP6). This study, therefore, contributes to further the understanding of recent flood hazards in Africa, and identifies regions that will likely become more vulnerable to climate change and its decadal variability over the decades to come.