Quantifying the Impact of Temporal and Spatial Heterogeneity in Turbulence on Bed‐Load Transport Over Vegetated Beds Under Wave‐Current Conditions

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Abstract
Laboratory experiments measured velocity and bedload transport in vegetated channels under current‐dominated, combined wave‐current conditions. Waves and vegetation, respectively, introduced temporal and spatial heterogeneity in the velocity, which significantly impacted sediment transport rate. Compared to pure‐current, the addition of waves only moderately increased (<40%) the time‐mean turbulent kinetic energy (TKE) but introduced temporal peaks in TKE that triggered an exponential increase in sediment transport. Similarly, local regions of intense TKE, reflected in the TKE spatial variance, enhanced channel‐average sediment transport. The TKE spatial variance decreased with increasing area density of vegetation stems, such that the influence of spatial variance was strongest in sparse canopies. The impacts of spatial and temporal heterogeneity were incorporated into a new model for bedload transport, which significantly improved prediction. The enhancement in sediment transport from both temporal and spatial heterogeneity is most significant when hydrodynamic forcing is near the critical threshold for sediment motion.
Funding Information
  • National Natural Science Foundation of China (12272349)
  • National Natural Science Foundation of China (52339005)

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