101. Recent Changes in Hydroclimatic Patterns over Medium Niger River Basins at the Origin of the 2020 Flood in Niamey (Niger)
- Author
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Elisa Sauzedde, Leandro Rocchi, Alessandro Pezzoli, Théo Vischel, Sara Burrone, Giovanni Massazza, Gaptia Lawan Katiellou, Gérémy Panthou, Vieri Tarchiani, Mohamed H. Ibrahim, Andrea Terenziani, Edoardo Fiorillo, Maurizio Rosso, Tiziana De Filippis, Maurizio Tiepolo, Maurizio Bacci, Luc Descroix, Università degli studi di Torino (UNITO), Consiglio Nazionale delle Ricerche Area della Ricerca di Pisa (CNIT), Patrimoines locaux, Environnement et Globalisation (PALOC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU), Air Liquide Healthcare, Air Liquide [Siège Social], Dpt of Physical Science [Nigeria], Landmark University, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), University of Turin, Politecnico di Torino = Polytechnic of Turin (Polito), and Università degli studi di Torino = University of Turin (UNITO)
- Subjects
Disaster risk reduction, River flood, Early warning systems, Runoff coefficients, Hazard, CHIRPS, Niger, Niamey ,Wet season ,TerraClimate ,010504 meteorology & atmospheric sciences ,Geography, Planning and Development ,0207 environmental engineering ,Drainage basin ,02 engineering and technology ,flood risk ,River flood ,Aquatic Science ,Structural basin ,01 natural sciences ,Biochemistry ,Early warning systems ,Urbanization ,Sahel ,Middle Niger River Basin ,Disaster risk reduction ,Niger ,Precipitation ,rating curves ,020701 environmental engineering ,TD201-500 ,0105 earth and related environmental sciences ,Water Science and Technology ,CHIRPS ,Hydrology ,geography ,geography.geographical_feature_category ,Niamey ,Water supply for domestic and industrial purposes ,Flood myth ,Hydraulic engineering ,runoff coefficients ,floods ,early warning system ,levees ,hazard thresholds ,13. Climate action ,[SDE]Environmental Sciences ,Environmental science ,TC1-978 ,Levee ,Surface runoff ,Hazard - Abstract
International audience; Niamey, the capital of Niger, is particularly prone to floods, since it is on the banks of the Niger River, which in its middle basin has two flood peaks: one in summer (the red flood) and one in winter (the black flood). In 2020, the Niger River in Niamey reached its all-time highest levels following an abundant rainy season. On the other hand, the floods in Niamey have been particularly frequent in the last decade, a symptom of a change in hydroclimatic behaviour already observed since the end of the great droughts of the 1970s and 1980s and which is identified with the name of Sahelian Paradox. This study, starting from the analysis of the 2020 flood and from the update of the rating curve of the Niamey hydrometric station, analyses the rainfall–runoff relationship on the Sahelian basins of the Medium Niger River Basin (MNRB) that are at the origin of the local flood. The comparative analysis of runoffs, annual maximum flows (AMAX) and runoff coefficients with various rainfall indices calculated on gridded datasets allowed to hydroclimatically characterise the last decade as a different period from the wet one before the drought, the dry one and the post-drought one. Compared to the last one, the current period is characterised by a sustained increase in hydrological indicators (AMAX +27%) consistent with the increase in both the accumulation of precipitation (+11%) and the number (+51%) and magnitude (+54%) of extreme events in the MNRB. Furthermore, a greater concentration of rainfall and extremes (+78%) in August contributes to reinforcing the red flood’s positive anomalies (+2.23 st.dev in 2020). The study indicates that under these conditions the frequency of extreme hydrological events in Niamey will tend to increase further also because of the concurrence of drivers such as river-bed silting and levee effects. Consequently, the study concludes with the need for a comprehensive flood-risk assessment on the Niamey city that considers both recent hydroclimatic trends and urbanisation dynamics in flood zones hence defining the most appropriate risk-reduction strategies.
- Published
- 2021