The 3rd Hutchinson lecture: numerical modelling of forests with uprooting as a nature-based solution to mitigate flow-type landslides

Abstract To protect human lives and infrastructure in mountainous regions from flow-type landslides, engineered countermeasures, such as rigid and flexible barriers, are installed along predicted flow paths. Over recent years, research efforts in physical and numerical modelling have helped advance the understanding of impact mechanisms involved and enabled the optimization of the design of engineered solutions. With the advent of sustainable engineering, attention has shifted towards the use and development of nature-based solutions to impede flow-type landslides. A simple nature-based solution is to consider the effects of forests on the mobility of flow-type landslides. However, to leverage forests, the complex flow-stem interactions and effects of uprooting need to be captured. In this paper, details and results of a new GPU-empowered MPM-LSDEM numerical solver that simulates the effects of flows through tree stems that can uproot are presented along with systematic evaluation of the solver. Simulations of flow-forest interaction with and without uprooting show that forests have profound effects on flow forest interaction. For dense forests, uprooted stems can push flow material to enhance its runout distance. Additionally, uprooted stems tend to concentrate near the front of the flows even if they were evenly distributed throughout the model forest at the beginning. The impact force exerted by a stem can be considered concentrated loading and can damage barriers along the flow path. Taken together, hazard assessment tools that can model the effects of uprooting are crucial to close predictions of hazard extent (i.e., runout distance) and the design of physical countermeasures such as barriers.