Turbulence and Bedload Transport in Submerged Vegetation Canopies

Using a constant channel velocity, (Formula presented.), flume experiments investigated how canopy density ((Formula presented.), with canopy frontal area per unit volume (Formula presented.), and canopy height (Formula presented.)) and submergence ratio ((Formula presented.), with (Formula presented.) the flow depth) impacted near-bed velocity, turbulence, and bedload transport within a submerged canopy of rigid model vegetation. For (Formula presented.)  2, the near-bed TKE was insensitive to (Formula presented.) and (Formula presented.), because of a trade-off between decreasing stem-generated turbulence and increasing canopy-shear-generated turbulence, as (Formula presented.) and (Formula presented.) increased. However, the near-bed velocity declined with increasing (Formula presented.) and (Formula presented.), such that, even with a constant TKE, (Formula presented.) also declined. These trends highlight that both TKE and velocity were important in controlling bedload transport. Models to predict velocity, TKE, and bedload transport were developed and validated with measurements. The models were then used to explore conditions more relevant to the field, specifically with constant energy slope ((Formula presented.)) and flexible vegetation. For a constant energy slope, (Formula presented.) increased as (Formula presented.) decreased and as (Formula presented.) increased, which in turn influenced the in-canopy velocity and TKE. The highest (Formula presented.) occurred with the greatest (Formula presented.) and smallest (Formula presented.), corresponding to the highest (Formula presented.) and greatest contribution of canopy-shear-generated turbulence, reflecting the importance of canopy-shear-generated turbulence in submerged canopies. The lowest (Formula presented.) occurred with smallest (Formula presented.) and highest (Formula presented.), corresponding to the smallest (Formula presented.) and least contribution of canopy-shear-generated turbulence. © 2024. The Author(s).