Machine‐Assisted Physical Closure for Coarse Suspended Sediments in Vegetated Turbulent Channel Flows.

The parameterization of suspended sediments in vegetated flows presents a significant challenge, yet it is crucial across various environmental and geophysical disciplines. This study focuses on modeling suspended sediment concentrations (SSC) in vegetated flows with a canopy density of avH ∈ [0.3, 1.0] by examining turbulent dispersive flux. While conventional studies disregard dispersive momentum flux for avH > 0.1, our findings reveal significant dispersive sediment flux for large particles with a diameter‐to‐Kolmogorov length ratio when dp/η > 0.1. Traditional Rouse alike approaches therefore must be revised to account for this effect. We introduce a hybrid methodology that combines physical modeling with machine learning to parameterize dispersive flux, guided by constraints from diffusive and settling fluxes, characterized using recent covariance and turbulent settling methods, respectively. The model predictions align well with reported SSC data, demonstrating the versatility of the model in parameterizing sediment‐vegetation interactions in turbulent flows. Plain Language Summary: This research focuses on the movement of suspended sediments in rivers, specifically in areas with vegetation. Traditional models cannot depict this process, prompting the development of a new methodology that merges conventional scientific techniques with advanced machine learning. The proposed approach has demonstrated superior performance, particularly in transitional areas between vegetated and non‐vegetated zones. The significance of this study lies in its contribution to modeling an often‐overlooked spatial term (called "turbulent dispersive flux") by showing that its magnitude is much greater than conventionally supposed. This study also advances the current methodology of including physics‐based artificial intelligence to model sediment dynamics in vegetated river systems. The proposed approach is versatile and can be included in the large‐scale transport models. Key Points: Rouse budget without dispersive flux cannot describe coarse sediment concentration in vegetated flowsA machine‐assisted physical closure for turbulent dispersive flux from spatial average is proposedPredicted sediment concentration results agree with reported experimental data in the literature [ABSTRACT FROM AUTHOR]