Geo-environmental Study of Soils Within the Double Landslide Area of Foreke-Dschang (Cameroon Western Highlands)

Abstract

Humid tropical mountainous areas are often vulnerable to mass movements and thus necessitate an in-depth study for best management practices. The aim of this work is to characterize the soils of the Foreke-Dschang (Cameroon Western Highlands) double landslide area on a geotechnical and physico-chemical basis. In effect, this area recently experienced a tragic double landslide on 5th November 2024 causing considerable human and material loss. Field work involved landscape analysis, geological description, soil prospection and sample collection (rocks and soils). In the laboratory, rock thin sections were cut and observed under the microscope while soil samples were analyzed by standard procedures. Results indicate that the primary parent material of the soil is a granite-gneissic (basement). The geotechnical study of the soils shows a silty clayey texture, high porosity (>29%), high water saturation rate (>60% water), low cohesion (<0.5 bar) and high angle of internal friction (18°–25°). Such characteristics, alongside steep slopes (>30°), exceptionally heavy rainfall (>2500mm/year) in 2024, low (<2%) organic matter content (due to reconversion of the forest into cropland), vibrations generated by heavy traffic on the National Road No. 4, inappropriate agricultural practices on the slopes and absence of water drainage structures are at the origin of a translational type landslide. The implementation of drainage measures, slope reduction and grassing, construction of retaining walls and geotechnical developments to reinforce the stability of slopes along the road and the implementation of appropriate agroforestry practices are highly recommended to control soil movement.