This study investigates the role of tree removal in a landslide that occurred in Spain, where a historical fill supported by a retaining wall collapsed, damaging multiple buildings. An earlier ground movement, attributed to an overturning effect from tree loading at the crest, prompted the removal of vegetation. However, this intervention did not prevent the subsequent and more severe failure. The research aims to quantify the impact of this tree removal on slope stability. To understand the failure mechanism, a detailed timeline of events was reconstructed, and a comprehensive post-failure site characterization was conducted. These data were incorporated into a finite element method (FEM) numerical model that considers both the mechanical reinforcement provided by roots and the hydrological influence of partial soil saturation. The modelling approach reflects current advances in simulating vegetation effects on slope stability, particularly in unsaturated conditions. The results reveal that both root cohesion and partial saturation played significant roles in maintaining slope stability prior to failure. Their removal, through vegetation clearance and increased moisture due to an irrigation leak, contributed to the eventual collapse. This case study emphasizes the need to integrate biological and hydro-mechanical factors into slope stability analyses, which are often overlooked in conventional engineering practice. Overall, the findings demonstrate that vegetation management, if not carefully evaluated, can inadvertently reduce slope stability. Incorporating root reinforcement and unsaturated soil behaviour into numerical models offers a more realistic and robust framework for assessing landslide risk.
Ciantia et al. (Wed,) studied this question.