Scale constraints in a vegetated shear-layer

As discussed earlier, the velocity profile near the top of the canopy is characterized by a region of strong shear arising from the discontinuity in drag. In this region the 

The canopy dissipation, ec, represents the damping of shear-scale turbulence by canopy drag (e.g. Wilson [648]) 

Finally, the viscous dissipation, ev, is generally negligible relative to the canopy dissipation (Wilson, 1988 [648]). 

As described above, terms b, c, and d, as well as the viscous dissipation, ev, may be neglected from a first-order energy budget within the shear-layer. The remaining terms suggest that the vortex (and shear-layer) growth will be arrested (D(ks)/Dt = o) when the shear-production balances the canopy dissipation. This balance implies 

The turbulence statistics included in the right-hand-side of (6.38) have similar profile shapes across a free-shear-layer, with maximum values uw = -0.01 AC/2, u 2 = 0.03AU2,w 2 = 0.015AU2, and v 2 = 0.02AU2, where AU = u2 - ux is the velocity 

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