A Two‐Layer Turbulence‐Based Model to Predict Suspended Sediment Concentration in Flows With Aquatic Vegetation.

Traditional bed shear stress‐based models (e.g., Rouse model) derived from the classic parabolic profile of eddy viscosity in open‐channel flows fail to accurately predict suspended sediment concentration (SSC) in flows with aquatic vegetation. We developed a two‐layer, turbulence‐based model to predict SSC profiles in emergent vegetated flows. Turbulence generated from vegetation, bed, and coherent structures caused by stem‐bed‐flow interaction are considered into the near‐bed turbulent kinetic energy (TKE) to calculate the effective bed shear velocity, ubeff*. The model, validated by experimental data, further showed that the thickness height of the near‐bed layer (effective bottom boundary layer), Hb, varies with flow velocity and canopy density. Two additional models are provided to estimate Hb and ubeff*. The model is expected to provide critical information to future studies on sediment transport, landscape evolution, and water quality management in vegetated streams, wetlands, and estuaries. Plain Language Summary: Aquatic vegetation serves important roles in wetlands, estuaries, riverine, and coastal areas. It provides shelter for living organisms, protects coastal and riverbank regions from waves, currents, and floods, and makes a contribution to the global carbon circulation. However, under various scenarios of environmental change, the presence of aquatic vegetation continuously decreased in these areas during recent decades. To improve restoration efforts and protect vegetation habitats, understanding vegetation‐sediment dynamics is a paramount and will lead to more accurate models of landscape evolution and water quality management. Traditional suspended sediment models widely applied in open‐channel flows, do not work in regions with aquatic plants. We propose a modified model to predict suspended sediment concentration in vegetated flows, validated with experimental data. The new model showed that near‐bed turbulence generated by bed‐vegetation‐flow interaction is as important as the bed‐ and vegetation‐generated turbulence considered separately. The model is expected to provide critical information for future studies on sediment transport, landscape evolution, and water quality management in vegetated streams, wetlands, and estuaries. Key Points: We present a two‐layer, turbulence‐based model to predict suspended sediment concentration (SSC) in flows with emergent vegetationWe include coherent structures generated by stem‐bed‐flow interactions to calculate near‐bed turbulent kinetic energyWe derive models for effective boundary layer thickness and effective bed shear velocity to predict SSC [ABSTRACT FROM AUTHOR]