Sustainable Assessment of Vetiver-Based Nature-Based Solutions for Landslide Hazard Mitigation Under Groundwater, Surcharge, and Pseudo-Static Seismic Conditions

Sustainable landslide hazard mitigation requires scenario-based assessment of nature-based solutions under realistic hydromechanical and multi-hazard conditions. This study evaluates the mechanical effect of Vetiver grass ( Chrysopogon zizanioides ) on slope stability in Loja, southern Ecuador, through an integrated framework combining geotechnical characterization, direct shear testing, finite element modelling, limit equilibrium analysis, and targeted statistical evaluation. Three fine-grained soils, classified as CH, MH, and ML, were analysed under baseline groundwater conditions, groundwater with an 8 kN/m 2 surcharge, and groundwater with surcharge plus pseudo-static seismic loading. Vetiver reinforcement increased apparent cohesion by 8.92–27.65% and internal friction angle by 6.90–17.43%, with the highest cohesion gain in ML soil. Numerical results showed that stabilization was controlled by soil type, slope geometry, loading condition, and interaction between the 2.0 m root-reinforced layer and the governing failure mechanism. Under surcharge loading, FS for ML at 0.5H:1V increased from 1.056 to 1.450. Under combined loading, FS increased from 0.217 to 1.440 for ML at 1H:1V and from 0.587 to 2.060 for CH at 1H:1V. Targeted ANOVA/MANOVA for MH soil confirmed the influence of geometry and combined loading. Therefore, Vetiver should be considered a complementary, site-specific, and risk-informed mitigation measure rather than a universal stabilization solution.