When a tree falls into a river becomes instream large wood and promotes fundamental changes in river hydraulics and morphology, playing a relevant role in river ecology. By interacting with the flow and sediment, the instream large wood (i.e., downed trees, trunks, root wads and branches) contributes to maintaining the river's physical and ecological integrity. However, large quantities of wood can be transported and deposited during floods, enhancing the adverse effects of flooding at critical sections like bridges. Accurate predictions of large wood dynamics in terms of fluxes, depositional patterns, trajectories, and travel distance, still need to be improved, and observations remain scarce. Only recently, numerical models can help to this end.
In contrast to other fluvial components such as fluid flow and sediment, for which numerical models have been extensively developed and applied over decades, numerical modelling of wood transport is still in its infancy. In this talk, I will describe the most recent advances and challenges related to the numerical modelling of instream large wood transport in rivers, focusing on the numerical model Iber-Wood. Iber-Wood is a two-dimensional computational fluid dynamics model that couples a Eulerian approach for hydrodynamics and sediment transport to a discrete element (i.e., Lagrangian) approach for wood elements. The model has been widely validated using flume and field observations and applied to several case studies and has been proven to accurately reproduce wood trajectories, patterns of wood deposition, and impacts of wood accumulations during floods.