Impacts socio-économiques et environnementaux des risques d’inondation dans le bassin versant de l’Oti au Togo (Afrique de l’Ouest)

The Oti River watershed, in Togo, is currently confronted with climate variability phenomena characterised by recurrent flooding events that weaken human and environmental systems. The objective of this study is to analyse the socio-economic and environmental impacts of floods in the Oti watershed in Togo. To this end, rainfall data (daily rainfall from 1961-2017), hydrometric data (daily flows from 1961-2017) and epidemiological data from the Mango health district were used. Similarly, agricultural statistics and socio-economic survey data were used. Rainfall and flow anomaly indices and McKee's (1993) classification were used to characterise flood hazard thresholds. Field surveys were carried out among the population to find out the impacts caused by floods in the watershed. The results show that 1962, 1964 and 2015 were extremely wet years and 1968, 1999, 2012 and 2013 are very wet years in the whole Oti watershed. The hydrometric indices show a significant variation in annual maximum flows from the 1960s onwards in the Oti sub-watershed of Mango and Mandouri. This means that the evolution in the series of maximum flows is linked to the extreme daily rainfall. The risk of flooding in the watershed has socio-economic, health and environmental impacts. These impacts can be summarised as loss of human life, precious objects and income of economic actors, increase in cases of diarrhoeal diseases and malaria, psychological scars of victims, soil erosion, loss of plant and animal biodiversity, water and nature pollution, etc