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Article

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

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Dipartimento Interateneo di Scienze, Progetto e Politiche del Territorio (DIST), Politecnico di Torino & Università di Torino, 10129 Torino, Italy
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Agenzia Interregionale per Il Fiume Po (AIPo), 10024 Moncalieri, Italy
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Istituto per la BioEconomia–Consiglio Nazionale delle Ricerche (IBE-CNR), 50019 Sesto Fiorentino, Italy
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Unité Mixte de Recherche Patrimoines Locaux, Environnement & Globalisation (PALOC), Institut de Recherche pour le Développement (IRD), Muséum National d’Histoire Naturelle (MNHN), Sorbonne Université, 75231 Paris, France
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Direction de l’Hydrologie (DH), Ministère de l’Hydraulique et de l’Assainissement du Niger, Niamey 8004, Niger
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Direction de la Météorologie Nationale (DMN), Ministère des Transports du Niger, Niamey 8001, Niger
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Institut des Géosciences de l’Environnement, Université Grenoble Alpes, 38058 Grenoble, France
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Dipartimento di Ingegneria dell’Ambiente, del Territorio e delle Infrastrutture (DIATI), Politecnico di Torino, 10129 Torino, Italy
*
Author to whom correspondence should be addressed.
Academic Editor: Margarida Lopes Rodrigues Liberato
Water 2021, 13(12), 1659; https://doi.org/10.3390/w13121659
Received: 29 March 2021 / Revised: 7 June 2021 / Accepted: 9 June 2021 / Published: 14 June 2021
(This article belongs to the Special Issue Assessment of Hydrological and Hydro-Meteorological Extreme Events)
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. View Full-Text
Keywords: Middle Niger River Basin; Niamey; Sahel; floods; rating curves; runoff coefficients; early warning system; flood risk; levees; hazard thresholds; CHIRPS; TerraClimate Middle Niger River Basin; Niamey; Sahel; floods; rating curves; runoff coefficients; early warning system; flood risk; levees; hazard thresholds; CHIRPS; TerraClimate
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MDPI and ACS Style

Massazza, G.; Bacci, M.; Descroix, L.; Ibrahim, M.H.; Fiorillo, E.; Katiellou, G.L.; Panthou, G.; Pezzoli, A.; Rosso, M.; Sauzedde, E.; Terenziani, A.; De Filippis, T.; Rocchi, L.; Burrone, S.; Tiepolo, M.; Vischel, T.; Tarchiani, V. Recent Changes in Hydroclimatic Patterns over Medium Niger River Basins at the Origin of the 2020 Flood in Niamey (Niger). Water 2021, 13, 1659. https://doi.org/10.3390/w13121659

AMA Style

Massazza G, Bacci M, Descroix L, Ibrahim MH, Fiorillo E, Katiellou GL, Panthou G, Pezzoli A, Rosso M, Sauzedde E, Terenziani A, De Filippis T, Rocchi L, Burrone S, Tiepolo M, Vischel T, Tarchiani V. Recent Changes in Hydroclimatic Patterns over Medium Niger River Basins at the Origin of the 2020 Flood in Niamey (Niger). Water. 2021; 13(12):1659. https://doi.org/10.3390/w13121659

Chicago/Turabian Style

Massazza, Giovanni, Maurizio Bacci, Luc Descroix, Mohamed H. Ibrahim, Edoardo Fiorillo, Gaptia L. Katiellou, Geremy Panthou, Alessandro Pezzoli, Maurizio Rosso, Elisa Sauzedde, Andrea Terenziani, Tiziana De Filippis, Leandro Rocchi, Sara Burrone, Maurizio Tiepolo, Théo Vischel, and Vieri Tarchiani. 2021. "Recent Changes in Hydroclimatic Patterns over Medium Niger River Basins at the Origin of the 2020 Flood in Niamey (Niger)" Water 13, no. 12: 1659. https://doi.org/10.3390/w13121659

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