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Flow Structures Within Aquatic Vegetation under Combined Current and Wind-driven Wave Conditions: Field Observations in Floodplains of Poyang Lake, China
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  • Yinghao Zhang,
  • Xijun Lai,
  • Jingxu Ma,
  • Qian Zhang,
  • Ru Yu,
  • Xin Yao,
  • Huanguang Deng
Yinghao Zhang
Liaocheng University
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Xijun Lai
Nanjing Institute of Geography and Limnology Chinese Academy of Sciences
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Jingxu Ma
Liaocheng University
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Qian Zhang
Liaocheng University
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Ru Yu
Liaocheng University
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Xin Yao
Liaocheng University
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Huanguang Deng
Liaocheng University
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Abstract

Field measurements were conducted in floodplains of Poyang Lake (China) to study the influence of aquatic vegetation on flow structures under combined current and wave conditions. Wave and turbulent velocity components were decomposed from the time series of instantaneous velocity and analyzed separately. With weak wave-plant interaction, indicated as the ratio of wave excursion to stem spacing Ew/S < 0.5 in present study, the vertical distributions of time-averaged velocity (Uhoriz) and turbulent kinetic energy (TKE) with the presence of vegetation were similar to that under pure current conditions. For emergent conditions, Uhoriz and TKE distributed uniformly through the entire water column or increased slightly toward the water surface. Similar distributions were present in the lower part of submerged vegetation, above which the Uhoriz and TKE increased with increasing distance to bed bottom and TKE reached its maximum near the top of vegetation. With small Ew/S the wave orbital velocity (Uw) was not attenuated within vegetation compared with that above the vegetation or near the water surface, and Uw through the entire water column can be predicted by the linear wave theory. However, the turbulence generated near the top of canopy can penetrate a deeper depth into vegetation with the presence of wind-driven waves than without.