Author(s): Hanwen Cui; Stefan Felder
Linked Author(s): Stefan Felder
Keywords: Eco-hydraulics; Friction factor; Vegetated waterways; Nature-based solutions; Physical modellin
Abstract: High-velocity supercritical flows down grassed spillways are characterized by complex hydraulic behavior that presentssignificant experimental and numerical challenges. In these flows, the grass canopy not only alters the flow structure by generating canopy-scale vortices, but the canopy is also continuously modified by scouring and erosion. Previous research on grassed spillways often assumed a static channel bed and reported time-averaged hydraulic properties, overlooking the influence of evolving channel bed conditions. Herein, this research investigated supercritical spillway flows along a grassed spillway with 10.8° slope, comparing the change of flow resistance during the erosion of three different real grass species. While all grass species showed time variation in friction factors, there were overall variations in flow resistance for different grass types. Couch grass with dense canopy demonstrated larger friction factors compared to Couch grass with sparser canopy and thicker underlying soil, while Buffalo grass had the highest flow resistance due to stronger root structures and wider canopies. The results emphasized the importance of considering time-variation in flow resistance, and provided practical guidance on grass cover for erosion protection of embankments.
Year: 2025