Spatiotemporal analysis and classification of flood-generating processes in the District of Abidjan using satellite-based rainfall estimates

Abstract Urban flooding is one of the most frequent and impactful natural disasters that significantly impacts communities in major cities of West Africa. Understanding the spatial and temporal variations of floods is essential for effective disaster management associated with them. This study presents the first comprehensive evaluation of satellite rainfall estimates (SREs) across the District of Abidjan, utilising an enhanced urban rain gauge network from 2019 to 2022. Using multiple SRE products, namely IMERG (EARLY and FINAL runs) and CHIRPS, we analyse the dynamics of urban flooding from 1990 to 2022, examine flood-generating processes, and assess seasonal and interannual flood variability through a geo-historical approach. In terms of SRE product performance, IMERG-EARLY stands out at the daily scale, whereas CHIRPS clearly performs better in detecting extreme rainfall values. Moreover, the findings reveal that approximately 210 flood events occurred in the District of Abidjan, with the majority (146, representing 70%) occurring in June. These events resulted in more than 350 casualties, including 170 deaths and 180 injuries, as well as considerable material and economic damages. Heavy rainfall events (> 30 mm day –1 ) constitute the most significant share across all datasets and municipalities, underscoring their critical role in triggering floods. Moreover, these flood events are classified to identify the different flood drivers: excess rainfall, prolonged rainfall, and short rainfall. Thus, the results revealed that nearly 75% of the identified flood events were linked to excessive or short-duration rainfall episodes, driven by soil saturation and intense precipitation occurring before and/or during the flood events. These findings could contribute to the development of effective flood risk management strategies, including early warning systems and policy measures that enhance urban resilience.