Recent Changes in Hydroclimatic Patterns over Medium Niger River Basins at the Origin of the 2020 Flood in Niamey (Niger)

Niamey, the capital of Niger, is particularly prone to floods, since it on banks Niger River, which in its middle basin has two flood peaks: one summer (the red flood) and winter black flood). In 2020, River Niamey reached all-time highest levels following an abundant rainy season. On other hand, floods have been frequent last decade, a symptom change hydroclimatic behaviour already observed end great droughts 1970s 1980s identified with name Sahelian Paradox. This study, starting from analysis 2020 update rating curve hydrometric station, analyses rainfall–runoff relationship basins Medium Basin (MNRB) that are at origin local flood. The comparative runoffs, annual maximum flows (AMAX) runoff coefficients various rainfall indices calculated gridded datasets allowed hydroclimatically characterise decade as different period wet before drought, dry post-drought one. Compared one, current characterised by sustained increase hydrological indicators (AMAX +27%) consistent both accumulation precipitation (+11%) number (+51%) magnitude (+54%) extreme events MNRB. Furthermore, greater concentration extremes (+78%) August contributes reinforcing flood’s positive anomalies (+2.23 st.dev 2020). study indicates under these conditions frequency will tend further also because concurrence drivers such river-bed silting levee effects. Consequently, concludes need for comprehensive flood-risk assessment city considers recent trends urbanisation dynamics zones hence defining most appropriate risk-reduction strategies.