Environmental Fluid Mechanics

, Volume 5, Issue 6, pp 527–551 | Cite as

Mass Transport in Vegetated Shear Flows



Submerged aquatic vegetation has the potential to greatly improve water quality through the removal of nutrients, particulates and trace metals. The efficiency of this removal depends heavily upon the rate of vertical mixing, which dictates the timescale over which these constituents remain in the canopy. Continuous dye injection experiments were conducted in a flume with model vegetation to characterize vertical mass transport in vegetated shear flows. Through the absorbance–concentration relationship of the Beer–Lambert Law, digital imaging was used to provide high-resolution concentration profiles of the dye plumes. Vertical mass transport is dominated by the coherent vortices of the vegetated shear layers. This is highlighted by the strong periodicity of the transport and its simple characterization based on properties of the shear layer. For example, the vertical turbulent diffusivity is directly proportional to the shear and thickness of the layer. The turbulent diffusivity depends upon the size of the plume, such that the rate of plume growth is lower near the source. In the far-field, mass is mixed more than twice as rapidly as momentum. Finally, plume size is dictated predominantly by X, a dimensionless distance that scales upon the number of vortex rotations experienced by the plume.


mass transport shear layer turbulence turbulent Schmidt number vegetated flow vortex 


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Copyright information

© Springer 2006

Authors and Affiliations

  1. 1.Centre for Water ResearchUniversity of Western AustraliaCrawleyAustralia
  2. 2.Ralph M. Parsons Laboratory, Department of Civil and Environmental EngineeringMassachusetts Institute of TechnologyCambridgeUSA

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