Author(s): Xinya Liang; Yunsong Wang; Jiarui Lei
Linked Author(s):
Keywords: Open channel flows Sediment erosion Nature-based solutions
Abstract: Submerged aquatic vegetation plays a crucial role in coastal and river ecosystems by reducing flow velocity and preventing sediment erosion. Although extensive research has explored the velocity profiles of submerged meadows covering entire channels, natural SAV distributions are often patchy and interact with three-dimensional velocity fields. Those near-bed turbulent intensities within vegetated flows, such as turbulent kinetic energy, dominate the sediment transport process. However, examining near-bed TKE within vegetated flows, as well as sediment transport, has rarely been addressed within existing theoretical frameworks. In this study, we investigate the complex physical mechanisms that govern flow-vegetation-sediment interactions through rigorous theoretical derivations and controlled laboratory experiments. A two-layer model was developed to predict the velocities and TKE both within and outside the 3-D meadows. Experimentally, we conducted flume experiments using rigid 3-D vegetation models, varying meadow density and width, and measured detailed flow fields across distinct zones. An RGB-D based sandbed reconstruction method was developed and was well-validated using the scales on each stem so that the scouring holes and ripple formations were quantified. Our results reveal a strong correlation between TKE and vegetation characteristics. The TKE outside the vegetation increases to triple the levels found within the meadow, significantly influencing bedform development and increasing the roughness height 5 to 13 times. Additionally, as the density and coverage of 3-D meadows increase, the magnitude of local scours around the stems decreases.
Year: 2025