Landslides in West Africa: Impact, mechanisms and management

Abstract

Enormous resources are lost to landslides annually in Africa. Expectations are that as the effect of climate-driven changes becomes more pronounced in the continent, the frequency, distribution and severity of landslides will change significantly. To adapt and survive any resulting changes in their environment, the International Program on Landslides project 150 "Capacity building and the impact of climate-driven changes on regional landslide distribution, frequency and scale of catastrophe" designed a capacity-building curriculum that encompassed training and skill acquisition. Under this project, students, professionals and laymen interact to learn, brainstorm and seek effective ways of managing landslides and other related geo-hazards. The interaction has led to the understanding that in West Africa's unique circumstances, investment in applied research should be the first step toward a safer environment. As a way of minimizing the huge amount of human and material resources lost to landslides, the International Program on Landslides project 150 assessed the impact and mechanism of landslides in some West African countries. Findings show that the impact varied greatly with topography, geomorphology, amount of rainfall, intensity of excavation activities and human population. On the other hand, while geology and climate played significant roles in landslide mechanisms, the particular mechanism leading to debris flows and debris avalanches in the West African region was similar regardless of locality. Most of the landslides in West Africa occur during the rainy season when heavy and prolonged rainfall trigger mass movements that are often catastrophic. Although the landslides occur in igneous, metamorphic and sedimentary terrains, most of the documented debris flows and debris avalanches have occurred in nonsedimentary terrains. Some landslides that are a good representation of most other landslides have been selected and used to explain the impact, mechanisms and management of landslides in West Africa. The major aim of this on-going project is to produce a regional landslide risk map and to install alert systems at the most threatened and vulnerable localities, such as the mountainous areas of Benue state, Nigeria.