Predicting bedload transport through river vegetation

A river’s ecosystem is significantly impacted by its aquatic vegetation. The self-purification capacity and healthy habitat provided by plants contribute to biodiversity within the river. While terrestrial vegetation serves to block wind and fix sand, aquatic vegetation reduces water flow velocity and influences the movement of sediment particles. However, the health of this system is impacted by riverbed scours and sediment deposition.

Understanding bedload transport — large particles such as sand and gravel rolling or sliding along a riverbed — is essential for ecological river restoration. The Meyer-Peter-Müller formula predicts bedload transport rate in vegetated flows, but its predictions are often compromised because of challenges associated with the precise estimation of bed shear stress.

Wang et al. modified the coefficients of the Meyer-Peter-Müller formula and developed a novel predictive formula for the bedload transport rate grounded in an effective bed shear stress model tailored for vegetated flows.

“By studying and constructing appropriate hydraulic and vegetation parameters, it becomes possible to quantify the impact of vegetation on bedload sediment transport in rivers,” said author Xiang Wang. “This understanding is crucial for comprehending changes in riverbed morphology and holds significant importance for ecological restoration efforts in river systems.”

The team determined that energy loss generated by vegetation is characterized through turbulent kinetic energy and developed their bed shear stress model through direct measurement. The resulting formula proved to be more precise than existing models.

“Our simplified formula offers a more accurate prediction of bedload transport rates in vegetated flows, making it suitable for use in computational fluid dynamics models and with potential extensions to real-world applications,” said Wang.

Source: “An improved formula for bed-load rate in open channel flows with emergent vegetation,” by Xiang Wang, Carlo Gualtieri, Wenxin Huai, Honghua Liu, and Songli Yu, Physics of Fluids (2024). The article can be accessed at https://doi.org/10.1063/5.0185667 .

This paper is part of the Flow and Plants Collection, learn more here.