Seismic Risk Analysis for Large Dams in West Africa Region

Dams are critical infrastructures, the failure of which would cause a catastrophic effect on a regional scale. West Africa has more than 150 large dams across the region, constructed in strategic locations which pose a potential risk for people and properties at the downstream paths. A method of seismic risk analysis for large dams within the West Africa region is discussed to evaluate the seismic hazard rating at the dam sites and the risk rating of its appurtenant structures. Although the study region is considered as a stable continental, two major earthquakes with casualty figures have been reported in Ghana and Guinea areas of the study basins in 1939 and 1983, respectively. This paper summarizes the procedures for analyses seismic risk and explain the seismic hazards of seventeen large dams selected within the study basins based mostly on the significance of each dam and location of earthquakes in and around the dam sites. The results show the values of peak ground acceleration (PGA) at dam sites ranges from 0.02 g to 0.45 g. A hazard map of PGA indicating preliminary analysis of dam structures was developed for the study basins. Based on the results of this analyses, 59% of the analysed dams identified as high-risk dams while the rest dams fall within the moderate-risk class. These dams require further analyses for their safety to protect the populace and the built environments along the downstream paths.