The Evolution of Hydrodynamic Intensities and Sediment Erosion Along Submerged Aquatic Vegetation

Abstract

Submerged aquatic vegetation, a key component of these solutions, 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 submerged aquatic vegetation distributions are often patchy and interact with three-dimensional velocity fields. Although some studies have shown that vegetation patches improve sediment deposition, the effects of 3-D meadows on flow structures and sediment transport remain unclear. This study aims to investigate the physical mechanisms underlying flow-vegetation-sediment interactions. By combining theoretical derivations and laboratory experiments, we examine the impact of 3-D submerged artificial vegetation on sediment transport and flow development in unidirectional flows. Our results reveal a strong correlation between turbulent kinetic energy, vegetation characteristics, and the co-evolved sand bedforms. The root mean square error of our turbulence prediction model, which includes vegetation factors and sand bed friction, is less than 10% in the fully developed region. Furthermore, in the presence of 3-D meadows, the TKE outside the vegetation increases to triple the levels found within the meadow, significantly influencing bedform development and increasing the roughness height $\left(k_s\right)$ 5 to 13 times. The bedform characteristics such as ripple length and steepness, conversely act as the indicator of the near-bed TKE strength. Additionally, local scours around vegetation stems and the overall development of the sand bed correlate with hydrodynamic intensities. As the density and coverage of 3-D meadows increase, the magnitude of local scours around the stems decreases.