Turbulence Dictates Bedload Transport in Vegetated Channels Without Dependence on Stem Diameter and Arrangement.

Vegetation provides habitat and nature‐based solutions to coastal flooding and erosion, drawing significant interest in its restoration, which requires an understanding of sediment transport and retention. Laboratory experiments examined the influence of stem diameter and arrangement on bedload sediment transport by considering arrays of different stem diameter and mixed diameters. Bedload transport rate was observed to depend on turbulent kinetic energy, with no dependence on stem diameter, which was shown to be consistent with the impulse model for sediment entrainment. Existing predictors of bedload transport for bare beds, based on bed shear stress, were recast in terms of turbulence. The new turbulence‐based model predicted sediment transport measured in model canopies across a range of conditions drawn from several previous studies. A prediction of turbulence based on biomass and velocity was also described, providing an important step toward predicting turbulence and bedload transport in canopies of real vegetation morphology. Plain Language Summary: Coastal and floodplain vegetation, such as saltmarsh and mangrove forest, damps current, waves, and storm surge, which can reduce flooding, prevent erosion, promote nutrient and soil carbon retention, and provide habitat that supports biodiversity. There is significant interest in the restoration and maintenance of these important ecosystems, which requires an understanding of sediment intake and retention. This study revealed that within regions with vegetation, the transport of sediment maintaining close contact with bed (called bedload) is determined by the intensity of turbulence but does not directly depend on stem diameter, which means that a prediction of turbulence intensity is sufficient to predict bedload transport. A prediction of turbulence intensity based on vegetation biomass and velocity was also described, providing an important step toward describing turbulence and bedload transport within vegetated regions, enabling prediction of coastal and riverbank evolution, which can provide insights into wetland protection and restoration. Key Points: In vegetation canopies, bedload transport can be predicted from turbulent kinetic energy, with no dependence on stem size or distributionThe critical turbulent kinetic energy for sediment motion can be estimated from incipient thresholds defined previously by bed shear stressTurbulence and bedload within vegetation may be predicted from biomass and velocity [ABSTRACT FROM AUTHOR]