Hydro-mechanical effects of deciduous forest on slope stability: First results from a case study in Western Norway

¹ The Norwegian Geotechnical Institute, Natural Hazards, Sandakerveien 140, 0484 Oslo, Norway
² University of Oslo, Physical geography and Hydrology, Sem Sælands vei 1, 0371 Oslo, Norway

^* Corresponding author: amanda.johansen.dibiagio@ngi.no

Abstract

The use of vegetation as a nature-based solution for shallow landslide risk reduction is receiving increased attention in the scientific community, as plants can provide hydro-mechanical reinforcement of slopes. Although numerous studies on this topic are well-documented in the literature, the hydro-mechanical effects of vegetation on partially saturated slopes under Nordic conditions remain unexplored. In this study, the first results from a newly established case study site located in Western Norway are presented. The study site is situated on a natural slope partially used as hayfield and partially covered by deciduous forest. The study includes an assessment of both the hydrological and mechanical reinforcement effects of the forest, as compared with the control scenario represented by the hayfield. Reinforcement effects analysed include changes in soil suction and volumetric water content induced by the forest and mechanical root reinforcement acting on the basal plane of a potential slip surface. The preliminary results show that the deciduous forest significantly contribute to slope stability through both hydrological and mechanical reinforcement. Despite the short monitoring period, these results provide valuable insights into the role of deciduous forest in mitigating shallow landslides in Western Norway.