RAINFALL TRENDS AND FLOOD FREQUENCY ANALYSES IN THE LOWER MONO RIVER BASIN IN TOGO, WEST AFRICA

Author : Joshua Ntajala, Benjamin L. Lampteyb, Jean Mianikpo Sogbedjic , Wilson-Bahun K. Kpotivid, .

Summary:

ABSTRACT
Flooding is the most devastating hydro-meteorological disaster in Togo leading to death of people and destruction of socioecological sys-tems each year, which calls for rainfall and return period analyses to help plan early warning systems. Hence, the foucus of this study was to examin the trend of rainfall in the basin and also estimate flood return periods, and the associated magnitude of river flow. The study em-ployed Gumbel’s Generalized Extreme Value (GEV) and Goodrich Exponential Distribution in trend and flood frequency estimation. The pat-tern of rainfall in the entire Mono Basin was considered due to the fact that the cause of flooding at the downstream is partly due to ex-treme high rainfall in the upstream. The results revealed a significant decreasing trend in rainfall is observed at the station of Sokode (up-stream), while an insignificant increase in rainfall is observed in the downstream (Atakpame, Sotouboua, Aklakou and Tabligbo). The results also show that the lower part of the Mono River Basin is likely to be mostly affected by 2-year and 5-year floods. The magnitudes of 2-year and 5-year floods are also found to be 567.4 m3/s and 847.1 m3/s respectively. Floods with annual return periods are also observed but are considered as the normal flow of the river with little or no impacts on the communities.

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