Laboratory simulations of wave attenuation by an emergent vegetation of artificial phragmites australis: an experimental study of an open-channel wave flume

Yiping L. et al., 2015. Journal of environmental engineering and landscape management

Original research (primary data)
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This paper presents a well-controlled laboratory experimental study to evaluate wave attenuation by artificial emergent plants (Phragmites australis) under different wave conditions and plant stem densities. Results showed substantial wave damping under investigated regular and irregular wave conditions and also the different rates of wave height and within canopy wave-induced flows as they travelled through the vegetated field under all tested conditions. The wave height decreased by 6%–25% at the insertion of the vegetation field and towards the downstream at a mean of 0.2 cm and 0.32 cm for regular and irregular waves respectively. The significant wave height along the vegetation field ranged from 0.89–1.76 cm and 0.8–1.28 cm with time mean height of 1.38 cm and 1.11 cm respectively for regular and irregular waves. This patterns as affected by plant density and also location from the leading edge of vegetation is investigated in the study. The wave energy attenuated by plant induced friction was predicted in terms of energy dissipation factor (fe) by Nielsen’s (1992) empirical model. Shear stress as a driving force of particle resuspension and the implication of the wave attenuation on near shore protection from erosion and sedimentation was discussed. The results and findings in this study will advance our understanding of wave attenuation by an emergent vegetation of Phragmites australis, in water system engineering like near shore and bank protection and restoration projects and also be employed for management purposes to reduce resuspension and erosion in shallow lakes.

Case studies

Basic information

  • Case ID: INT-235-1
  • Intervention type: Created habitats
  • Intervention description:

    experiments were conducted in an open wave flume constructed in the Coastal, Harbor and O shore Engine- ering Hydraulics Laboratory at Hohai University, China. A series of experimental runs were performed for waves propagating over an array of plastic artifcial emergent plants Artifcial plastic plants were used in this study to simulate aquatic vegetation. these plants mimicked real species of common reed (Phragmites Australis). ey are produced from material to generate appropriate density and flexural rigidity to approximate the real plants as possible. e plants have biomechanical and morphological resemblance to the real species they mimic and were thus suitable to be used in our studies. four vegetation densities (stems/m2) ranging from 30 to 90 stems/m2 which represent a typical aquatic con gura- tion in most rivers in the eastern china

  • Landscape/sea scape ecosystem management: No
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Storm surge  Positive wave height reduction wave energy disipation changes in shear stress which is a driving force behind sediment resuspension and erosion - a proxy to infer how they may contribute to erosion reduction
    Coastal erosion  Positive wave height reduction wave energy disipation changes in shear stress which is a driving force behind sediment resuspension and erosion - a proxy to infer how they may contribute to erosion reduction
  • Approach implemented in the field: No
  • Specific location:

    Eastern china

  • Country: China
  • Habitat/Biome type: Created wetland |
  • Issue specific term: Not applicable


  • Notes on intervention effectivness: assess effectiveness by monitoring how the vegetation alter the outcome measures upon entering and moving through the vegetation as opposed to their initial values before entering the vegetation. but note they do not have a control, scenario with no vegetation also test how effectiveness varies depending on the density of the vegetation (find in some cases more effective with increasing density) "In this study it was established that shear stress which is a driving force behind sediment resuspension and erosion (Hamilton, Mitchell 1997) within the ow depth is subs- tantially reduced under emergent conditions as the wave- induced ow is reduced. "
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Not applicable
  • Compare effectivness?: No
  • Compared to the non-NBS approach: Not applicable
  • Report greenhouse gas mitigation?: No
  • Impacts on GHG: Not applicable
  • Assess outcomes of the intervention on natural ecosystems: No
  • Impacts for the ecosystem: Not reported
  • Ecosystem measures:
  • Assess outcomes of the intervention on people: No
  • Impacts for people: Not reported
  • People measures:
  • Considers economic costs: No
  • Economic appraisal conducted: No
  • Economic appraisal described:
  • Economic costs of alternative considered: No
  • Compared to an alternative: Not reported

Evaluation methodology

  • Type of data: Quantitative
  • Is it experimental: No
  • Experimental evalution done: Not applicable
  • Non-experimental evalution done: Empirical case study
  • Study is systematic: