Evaluating the Potential of Vetiver Grass Systems for Soil Erosion Control and Slope Stabilisation in Anambra State

This study evaluates the effectiveness of vetiver grass systems for soil erosion control and shallow slope stabilisation in the intensely gully-eroded terrain of Anambra State, South East Nigeria, combining field plot experiments with root mechanical analysis to characterise both hydrological and geotechnical stabilisation performance. Vetiver grass systems are internationally recognised as a versatile, low-cost bioengineering solution for erosion control on steep slopes, but their performance in the specific soil and rainfall conditions of South East Nigeria, characterised by highly erodible ultisols and extreme rainfall intensities, requires local empirical characterisation. Vetiver hedgerow plots were established at three sites with contrasting slope gradients in Nnewi, Awka South, and Anambra West Local Government Areas, with bare soil control plots maintained at each site. Runoff volumes and sediment concentrations were measured from instrumented bounded plots during natural rainfall events over two rainy seasons. Root tensile strength was measured on vetiver roots of different diameters using a tensiometer device, and root distribution profiles were characterised. Slope stability modelling using Bishop's simplified method incorporated root reinforcement parameters from the measured data. Results show that established vetiver hedgerows reduce plot-scale sediment yield by 87 percent relative to bare controls during the first year and 94 percent in the second year, attributable to flow velocity reduction and surface protection. Root tensile strength averages 40 megapascals, and root area ratio at the potential failure plane provides a calculated cohesion increment of 8 to 16 kilopascals. Slope stability modelling confirms that vetiver root reinforcement increases the safety factor by 0.3 to 0.5 for typical shallow landslide failure surfaces. Keywords: vetiver grass, erosion control, bioengineering, slope stabilisation, Anambra State.