Aquatic vegetation exposed to flowing waters in fluvial systems experiences physical forces imposed by flow and alters the surrounding flow via resistance forces. These interactions affect transport and mixing processes in natural streams and hence are of great importance for ecology of river ecosystems. Until recently the effect of vegetation on flow has been of primary interest only in respect to complex roughness characteristics imposed by vegetation on the river channel. Customary logarithmic law stemming from perturbed boundary layer approximation was used as an analytical framework for flows over vegetative canopies (Kouwen & Unny 1973; Murota et al. 1984; Stephan & Gutknecht 2002). However, recent laboratory studies with scaled model vegetation (Ghisalberti & Nepf 2002) have indicated that flow within and just above a canopy behaves more like a mixing layer rather than a boundary layer.