State of Rural Mountain Road Deterioration in the absence of Strategic Maintenance planning: case of Santa Bamenda Highway and the Bamenda Wum Road of the North West Region of Cameroon

Santa-Bamenda Highway (SBHW) and Bamenda Wum Road (BWR) are two major roads in the North West Region (NWR) which is situated mid-way along the continental sector of the Cameroon Volcanic Line (CVL). Defects along these roads were studied, dips of slopes and dimensions of landslides measured. Rock and soil samples were studied for their mineral contents and later the geotechnical engineering properties of the soil samples were determined. Base maps, satellite images and hydro-meteorological data for rainfall, temperatures and relative humidity of the road environment were analyzed. These roads have been cut across mountainous slopes 25°-90° of dip on lateritic regolith developed on granite and tertiary rhyolite and trachytes that measure 30m in some places. Hydro-meteorological conditions as daily temperatures that may reach 32° C, relative humidity of 97% and annual rainfall of 2400mm render these soils dusty during the dry season and vulnerable to landslide hazard during the rainy season. From laboratory results, these soils show Atterberg Limits and drops in strength values of angles of internal friction and cohesion with increased water content. In the absence of strategic road maintenance programmes, this road environment bears several small-volume, shallow, short-traveled and a few, deep, large-volume landslides triggered by rainfall which exacerbate the degradation of the roads emphasized by defects such as cracks, potholes, ruts, ravels, dust etc. We recommend that the road authorities promote research to develop various mixtures of chemical additives and local geo-materials as suitable stabilization products at reduced costs and adopt appropriate maintenance strategies for these roads.