A Turbulence-Based Bed-Load Transport Model for Bare and Vegetated Channels

Abstract

Previous studies have shown that sediment transport models based on bed shear stress (τ) are not accurate for regions with vegetation. The present study demonstrated that the inaccuracy arises from the influence of vegetation-generated turbulence. Bed-load transport rate, Qs, and near-bed velocity were measured in a sediment-recirculating flume with model vegetation of different vegetation volume fractions (ϕ) and with bare sand beds. At the same τ, the measured Qs increased with increasing ϕ, suggesting that vegetation-generated turbulence, which also increased with increasing ϕ, was augmenting the bed-load transport. At the same near-bed turbulent kinetic energy, kt, the Qs measured in both bare and vegetated channels agreed within uncertainty, suggesting that kt may be a more universal predictor of bed-load transport than bed shear stress. A τ-based bed-load transport model was reinterpreted as a kt-based model. The new kt-based model predicted the Qs measurements for both bare and vegetated channels.