An Assessment of Landslides along Mountain Forest Roads: Bamenda Ring Road Segment through Bafut and Befang Forests on the Cameroon Volcanic Line.

Abstract

Purpose: Landslides cause distress in communities worldwide, disrupt socio-economic activities and cause damage to roads infrastructure. The purpose of this study was to undertake a comprehensive assessment of the recurrent landslide events along the Bamenda Ring Road (BRR) segment through the Bafut and Bafang mountain forests in the North West Region of Cameroon, located along the Cameroon Volcanic Line (CVL).
 Methodology: Topographic and geologic map studies, foot-borne surveys, hydro-meteorological data analysis and soil permeability tests were employed to the study. Results at the time of this study reveal 35 new slide scarps in Bafut and 16 along the Befang forests.
 Findings: The topography culminates between 670-1300 m altitude, while more than 50% of the slopes in the study area are convex, the rest are convexo-linear, concave, while a few of them are linear. Natural slope gradients vary from 35-600, while prevalent number of slides occur on sub-vertical road-cut embankments. The slides are classified as small volume, short distance-travelled shallow translational than rotational debris flows. Base rocks of the study zone are essentially coarse-grained leucocratic granites with quartz, feldspars, biotite and muscovite minerals which appear liable to weathering. Meanwhile, residual soil samples are permeable, have increased pore water pressure and has a high liquefaction tendency due to its high clay content. The absence of recent or historic earthquakes suggests that causative factors of landslides could be linked to steep gradients, lithology, deep weathering profiles, considerable affinity for water of the weathered materials and prolonged rainy seasons. As such we highlight the contribution of the landslide hazard with the direct risk based on the extensive deterioration of the road characterized by multiple road defects and reduced socio-economic activities and the indirect risk linked to difficulties in the movement of goods and persons and management of resources.
 Recommendations: This study recommend present officials to improve on their documentation and skills in monitoring rainfall and landslide hazard and manage disaster emergency; sensitize the population on landslide hazard and associated risk. There is need for government to establish a road authority for the management of landslide hazard, disaster relief and the land inside and outside the road.