Two-Dimensional Numerical Modeling of Large Wood Transport in Bended Channels Considering Secondary Current Effects

The modeling of large wood (LW) transport in rivers has received increasing interest from researchers in the last decade due to the widely recognized role of LW concerning flooding risk. For this purpose, few 2D depth-averaged hydraulic models have been coupled with LW transport models. However, such models usually neglect the effects of secondary currents on LW trajectories in river bends. In this work, the model Iber-Wood was enhanced to simulate the effects of secondary currents in river bends on LW trajectories. The proposed methodology presents a new formulation for considering secondary current effects on the flow field derived from the Manning formula and considers a new approach for reproducing the surface flow field that develops at channel bends. The enhanced model was tested to reproduce a series of laboratory experiments on wood transport in a sharp channel bend. The methodology introduces two new parameters in the model related to the secondary current effects, that is, the secondary current intensity and the adaptation length. These parameters were calibrated using available data from laboratory experiments. The good agreement between observed and simulated dowel trajectories in a sharp channel bend validated the proposed approach to simulate LW transport in the case of secondary currents. The study of the transport of wood in rivers has grown tremendously over the last decades due to its beneficial influence on river habitat and potential hazards, especially regarding the interaction with in-channel structures (i.e., bridges). As field observations of large wood (LW) during floods are usually missing, LW transport dynamics is commonly studied using physical or numerical models. Numerical simulation of LW transport is the focus of the present work, to propose a new methodology to reproduce the transport of LW at river bends or meanders. To achieve this goal, a numerical model has been enhanced to simulate the effect of the hydrodynamics on the lateral drift of wood that can be commonly seen in river bends. The model was tested with previous laboratory experiments on wood transport in a sharp channel bend. Numerical results showed good agreement with observations, thus validating the proposed approach. We simulate the free surface velocity field in channel bends, including secondary helicoidal flows, by enhancing a 2D numerical modelWe implement a model for predicting the trajectories of large wood in tight channel bendsWe test the model by comparing the simulated trajectories with observations from previous laboratory experiments

Automated summary

In recent years, there has been increasing interest in the modeling of large wood transport in rivers. However, existing models often neglect the effects of secondary currents on wood trajectories in river bends. This study enhances a numerical model to simulate the effects of secondary currents on wood trajectories, and validates the proposed approach through laboratory experiments.