Publication Date:
2016-10-26
Description:
This laboratory study advances our understanding of sediment transport in vegetated regions, by describing the impact of stem density on the critical velocity, U c r i t , at which sediment motion is initiated. Sparse emergent vegetation was modeled with rigid cylinders arranged in staggered arrays of different stem densities. The sediment transport rate, Q s , was measured over a range of current speeds using digital imaging, and the critical velocity was selected as the conditions at which the magnitude of Q s crossed the noise threshold. For both grain sizes considered here (0.6-0.85mm and 1.7-2mm), U c r i t decreased with increasing stem density. This dependence can be explained by a threshold condition based on turbulent kinetic energy, k t , suggesting that near-bed turbulence intensity may be a more important control than bed shear stress on the initiation of sediment motion. The turbulent kinetic energy model unified the bare-bed and vegetated channel measurements.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
