5 Conclusions
Field experiments were conducted in floodplains of Poyang Lake, China,
to investigate the influence of AV on flow structures under combined
current and wind-driven wave conditions. Spectral decomposition was used
to decompose the wave and turbulent components from the instantaneous
velocity series, and the vertical distributions of time-averaged
velocity (Uhoriz ), wave orbital velocity
(Uw ) and turbulent kinetic energy (TKE )
with the presence of AV were analyzed separately. WithEw /S (= 0.03 ~ 0.3)
< 0.5 for all cases tested here the interaction between waves
and vegetation was weak and the vertical profiles ofUhoriz and TKE were more similar to that
under pure-current conditions. Without significant wave-induced current
generated within canopy, Uhoriz distributed
uniformly through the entire water column or increased gradually from
bed to water surface for emergent vegetation and in the lower part of
submerged vegetation. As Red varied between 3 and
90, no stem-generated turbulence was expected to produce within
vegetation, leading to the TKE within canopy was comparable for
all cases in present study. Near the top of submerged vegetation,Uhoriz increased rapidly with increasing distance
to the bottom, and shear turbulence was expected to be generated near
the canopy interface, leading to TKE reaching its maximum near
the vegetation interface and decrease toward both bed and water surface.
With weak wave-plant interaction, the measured Uwfor the vegetated cases agreed with predictions by linear wave theory
through the entire water column, suggesting that the wave velocity was
not attenuated by AV. Although the mean and turbulent flow structures
within vegetation were not altered by waves with weak wave-plant
interaction in present study, the shear turbulence generated at the top
of vegetation penetrated a deeper depth within vegetation with the
influence of waves than without.