A three-dimensional study of vegetation management on cut slopes

Infrastructure slopes often become covered in dense vegetation due to poor vegetation management. Despite increasing cohesion and enhancing slope stability, high water demand vegetation leads to serviceability problems, primarily towards the end of the summer. Drastic approaches, however, such as vegetation clearance, have caused instabilities during wet seasons. Therefore, appropriate, effective, and continuous vegetation management is of essence and should consider both biodiversity and the engineering asset, while accounting for the contribution of vegetation in battling climate change. Developing numerical methodologies and models can be particularly useful in acquiring insight into the complex mechanism and processes taking place during slope-plant-atmosphere interactions. The work presented here focused for the first time on combining three-dimensional (3D) stability and serviceability issues through the development of a 3D numerical model to investigate different vegetation management strategies for a slope covered in high evapotranspiration demand vegetation and suffering serviceability problems. Different 3D patterns of vegetation removal and of replacement with lower water demand vegetation were considered and the effect of each of these on the serviceability and stability of the slope during the subsequent year was examined. The results demonstrated that replacement was preferable to removal, as stability and serviceability should be considered concurrently, and that, occasionally, clearance may have detrimental effects not only on stability but also on serviceability. The importance of considering out-of-plane displacements, which have traditionally been ignored, was revealed, thus providing numerical evidence that a shift in field monitoring is required, to capture the three-dimensionality of the problem.