The Kayanga-Anambé watershed, located in Haute-Casamance (Senegal), is a strategic area for national food security, yet remains exposed to recurrent flooding that threatens hydro-agricultural developments. This study aims to map flood-susceptibility zones using an integrated approach combining Geographic Information Systems (GIS) with a multi-criteria model built on seven (7) parameters: Flow Accumulation, Rainfall Intensity, Land Use, Geology, Slope, Terrain Elevation, and Distance to drainage (FIGUSED). The methodology relies essentially on cross-referencing morphometric factors (slope, drainage density), climatic factors (rainfall intensity), and anthropogenic factors (land use, infrastructure). Data derived from digital elevation models and Sentinel-2 imagery were processed through an Analytic Hierarchy Process (AHP) to weight the influence of each parameter. The results highlight a strong susceptibility of the Anambé basin, exacerbated by gentle slopes and the rapid saturation of hydromorphic soils during monsoon peaks. The high-susceptibility zone (high and very high classes) totals 40.64% of the watershed area, that is 1257.46 km2, corresponding geographically to the Anambé basin and the floodplain of the Kayanga and its tributaries. The most represented class is high susceptibility, at nearly 28%, closely followed by moderate susceptibility at 25.52% of the total area, indicating an overall heightened susceptibility of the watershed to inundation. The resulting susceptibility map thus constitutes an essential decision-support tool for planning agricultural campaigns through SODAGRI and for protecting human settlements in tropical rural areas.
The interruption of natural reproduction in the Chinese sturgeon, Acipenser sinensis, is an urgent ecological concern, and the thermal mechanisms underlying its stepped deterioration warrant attention. To systematically elucidate these mechanisms, this study quantified thermal dynamics throughout the reproductive cycle using a multi-scale retrospective analysis of water temperature and historical spawning records. A pronounced, stepwise mismatch between Yangtze River water temperatures and the reproductive requirements of the Chinese sturgeon was identified, manifested as significantly intensified thermal stress and temporal delay. Kernel density estimation (KDE) was used to quantify the thermal requirements for overwintering gonadal development and spawning. Period-stratified statistical tests were then applied to evaluate the alignment between ambient thermal regimes and species-specific requirements. Based on the interdecadal evolution of this mismatch, an intersection analysis between seasonal cooling curves and median spawning temperature was introduced to evaluate synchrony between spawning dates and thermal cues. These analyses revealed that spawning dates passively followed the postponement of the thermal cue, whereas the preferred temperature remained fixed. Collectively, this study demonstrates that thermal mismatches have intensified stepwise through both absolute exceedance of overwintering thresholds and mistimed arrival of suitable spawning temperatures, leading to the sequential degradation of reproduction.
