Spatio-temporal variability of flooded areas in the Ouémé floodplain (Benin, West Africa) from 2015 to 2023

Ouémé floodplain, southern Benin, West Africa. The Ouémé floodplain is a vast hydrological system feeding the Nokoué lagoon via the Sô and Ouémé rivers, crossing an extensive wetland region. Driven by the African monsoon, this area is marked by pronounced seasonal and interannual hydrological variability, leading to recurrent flooding that significantly threatens local communities’ safety and livelihoods. This study aims to assess the spatio-temporal variability of flooded areas in the Ouémé floodplain from 2015 to 2023, using both in-situ measurements and satellite remote sensing. The analysis reveals a clear seasonal cycle of flooding, modulated by interannual variability. Sentinel-1A data show that flood extent fluctuates widely, ranging from 20 to 160 km², and identify the Sô region as the most flood-prone area. Importantly, the study detects a significant upward trend in flood extent over the study period. Flood dynamics are primarily governed by cumulative January–September rainfall, with a critical threshold of 1070 mm beyond which flooding expands rapidly. Altimetry data further indicate that a 6 m rise in water surface elevation north of the Ouémé river results in increased flood expansion. Temporary hydrological connections appear during flood events, adding complexity to floodplain hydrodynamics and enhancing connectivity across the basin. Overall, this study provides new insights into the mechanisms driving floods in the Ouémé floodplain using remote sensing. • We depict spatio-temporal variations of the Ouémé floodplain (Benin) using S-1A data. • Floods spread southwest and create hydrological connections across the floodplain. • Flood extent varies from 20 km 2 (2015) to 160 km² (2022). • Flood extent strongly increases once cumulative rainfall exceeds ∼1070 mm. • A 6-meter water-level rise north of the Ouémé river triggers flooding extent.