On the Effects of Turbulence Modulation Driven by Suspended Sediment Stratification in Emergent Rigid Canopies

Abstract

Aquatic vegetation has the potential to increase suspended sediment capture while also increasing sediment resuspension and bedload transport. Suspended sediment can induce density stratification, which modulates the turbulence in the water column. We derive a Rouse-based formulation for suspended sediment concentration (SSC) including the effect of sediment-induced density stratification. We perform Large Eddy Simulations of vegetated and non-vegetated channels to explicitly highlight the effect of stratification on SSC profiles. We found that the impact of stratification is dominant in the near-bed region within the bottom boundary layer, affecting both sediment resuspension and bedload transport. Stratification reduces the likelihood of both dominant sweep and ejection events in the near the bed region which may affect sediment entrainment and bedload transport. Modifications to existing models of sediment entrainment and bedload transport are suggested to account for the effects of sediment induced stratification in vegetated and non-vegetated channels.