Analyzing the effects of eco-DRR practices on slope stability in a landslide-prone transport corridor in the Western Ghats, India

Landslides pose a significant threat to infrastructure and human life, especially in mountainous roads that have poorly protected slopes. This study focuses on the Kallar-Ponmudi road corridor in the Western Ghats of Kerala, India, which is susceptible to rainfall-induced shallow landslides. To assess slope stability, we used the Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability (TRIGRS) model, a physics-based, GIS-integrated FORTRAN program that simulates the timing and distribution of shallow landslides triggered by rainfall. Using this model, high susceptibility regions were selected to evaluate the effectiveness of different ecosystem-based disaster risk reduction (eco-DRR) measures in stabilizing the slopes. Initially, geotechnical parameters were derived from soil samples collected from these selected unstable slopes and used in the laboratory to recreate (simulate) real-field conditions. Five different slope conditions were tested under artificial rainfall: natural (unprotected), jute mesh, synthetic mesh, shallow-rooted grass, and deep-rooted vegetation. Jute mesh is selected for its affordability, biodegradability, and excellent soil contact, which supports vegetation growth and regulates surface erosion whereas synthetic mesh is included for its durability, adaptability, and effectiveness in reinforcing soil and improving drainage. Vegetative solutions using shallow- and deep-rooted species are considered due to their ability to strengthen soil through root reinforcement. Additionally, shallow roots reduce surface erosion whereas deep roots facilitate improved shear strength and subsurface stability, while also being readily available and low-cost. The results show that vegetative measures, particularly deep-rooted plants like vetiver grass, significantly enhanced slope stability compared to other reinforcements. Thus, this study highlights the importance of site-specific ecological interventions in improving road resilience in landslide-prone terrains, giving much impetus to eco-DRR measures.