Integrated subsurface screening for bioengineering suitability and erosion control on a tropical cut slope

Tropical cut slopes are highly susceptible to erosion and shallow landslides because intense rainfall interacts with deeply weathered residual soils, yet bioengineering interventions are frequently designed without adequate subsurface characterization.This study aimed to conduct an integrated geological, geophysical, and geotechnical characterization of a tropical cut slope on the Kenny Hill Formation, Selangor, Malaysia, in order to evaluate its suitability for bioengineering.Field reconnaissance and weathering grade classification were combined with a two-dimensional electrical resistivity survey, soil penetration resistance, near-surface moisture content, and erosion rate measurements collected across three vegetation coverage plots over 24 months.The slope was classified as Grade III to IV weathered metasedimentary rock with a sandy clay loam surface texture.Resistivity imaging identified a high resistivity, coarse-textured near-surface layer of 20,000 to 360,000 Ωm at 0 to 5 m depth, overlying a low resistivity, moisture-affected zone of 300 to 800 Ωm at 5 to 14.8 m depth.Penetration resistance increased significantly under vegetation cover, reaching 4.4 kPa in the densely vegetated plot compared with 2.9 kPa in the control, while nearsurface moisture content and hydraulic conductivity rose progressively, and erosion rate declined by up to 74.04% relative to the initial condition.These results indicate that the near-surface zone provides mechanically, hydrologically, and ecologically favorable conditions for root establishment, whereas the deeper zone offers limited support for root anchorage.The corresponding reduction in erosion rate confirms that the subsurface conditions identified through this integrated approach translate into measurable improvement in slope performance.Overall, combining weathering grade classification, resistivity zonation, and penetration resistance testing provides a reliable, fielddeployable framework for screening tropical cut slopes prior to bioengineering intervention.