Flood Disaster Risk Mapping in the Lower Mono River Basin in Togo

Author : Joshua NTAJAL, 2015.


Flood disaster is the most devastating hydro-meteorological event in the Lacs District, Togo. Communities in the Lower Mono River Basin experience flooding almost every two years. In light of this, the study focused on assessment and mapping of flood disaster risk in six selected communities in the Lacs District. Specifically, the study examined the pattern of rainfall in the basin, estimated and predicted flood return periods and the associated magnitude of river flow and, also mapped the nature of flood risk in the area. The study combined GIS and Remote Sensing, and statistical methods in risk mapping and analysis. Weighted overlay tool in ArcGIS was used for flood risk mapping, while statistical methods were employed in trend and flood frequency predictions. The study considered the pattern of rainfall in the entire Mono Basin due to the fact that the cause of flooding at the downstream is partly due to high rainfall in the upstream (Mono River).
Significant decreasing trend in rainfall was found at the station of Sokode (upstream), while an insignificant increase in rainfall was observed at Atakpame, Sotouboua, Aklakou and Tabligbo. Flood return periods for each 2 years and 5 years are 567.4 m3/s and 847.1 m3/s respectively. The resultant risk map shows that all the communities are exposed to flood disaster risk but Agbanakin, Azime Dossou and Togbavi communities are found in areas with high risk levels. Positive attitude towards early warning systems, collaboration among disaster relief institutions and appropriate building codes were recommended towards reducing flood disaster risk.
Key Words: Flood Disaster, Flood Risk, Mapping, Return Period, GIS, Mono River Basin,