FLOODS RISKS IN THE MFOUNDI UPSTREAM DRAINAGE BASIN IN YAOUNDE: A RESPONSE TO CLIMATIC MODIFICATIONS OR TO HUMAN IMPACTS?

Located at 217 km of the estuary of the Wouri, the city of Yaoundé is exposedto seismic risks, to mass movement and mainly to flood risks. From 1980 to 2008, 128 floodshave been counted and caused important material damages and more than 70 deaths. The main goal of this paper is to show the role of climatic and human factors in the triggering and the expansion of flooding in the city of Yaoundé in general and in the Mfoundi upstream drainage basin in particular. In fact, it has been noted that although the annual rainfall has decreased from 60 mm after years 1980, we observed a tiny increase of rainfall during dries months, explaining therefore unexpected floods observed in the dry season. The urbanization of the drainage basin and its consequences (waterproofing, obstructions of gutter, bridge etc.)aggravate this phenomenon over the time.