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Front. Mar. Sci. | doi: 10.3389/fmars.2018.00449

Predicting current-induced drag in emergent and submerged aquatic vegetation canopies

 Arnold van Rooijen1, 2, 3, 4, 5*,  Ryan Lowe1, 2, 3, 5,  Marco Ghisalberti2, 3, 6, Mario Conde-Frias2, 3, 5 and Liming Tan7
  • 1School of Earth Sciences, Faculty of Science, University of Western Australia, Australia
  • 2Oceans Institute, University of Western Australia, Australia
  • 3Oceans Institute, University of Western Australia, Australia
  • 4Unit of Marine and Coastal Systems, Deltares, Netherlands
  • 5ARC Centre of Excellence for Coral Reef Studies, Australia
  • 6Department of Infrastructure Engineering, School of Engineering, University of Melbourne, Australia
  • 7Ocean College, Zhejiang University, China

Canopies formed by aquatic vegetation, such as mangroves, seagrass and kelp, play a crucial role in altering the local hydrodynamics in rivers, estuaries and coastal regions, and thereby influence a range of morphodynamic and biophysical processes. Prediction of the influence of canopies on these hydrodynamic processes requires a fundamental understanding of canopy drag, which varies significantly with both flow conditions and canopy properties (such as density and submergence). Although our knowledge on canopy drag has increased significantly in recent decades, a conclusive, physics-based description for canopy drag that can be applied to both emergent and submerged canopies is currently lacking. Here, we extend a new theoretical canopy drag model (that employs the velocity between canopy elements as the reference velocity) to submerged aquatic canopies. The model is validated for the first time with direct measurements of drag forces exerted by canopies across broad ranges of flow conditions and canopy density and submergence. The skill and broader applicability of the model are further assessed using a comprehensive set of existing experimental data, covering a broad range of natural conditions (including flexible vegetation). The resulting model provides a simple tool to estimate canopy drag forces, which govern hydraulic resistance, sediment transport and biophysical processes within aquatic ecosystems.

Keywords: Ecohydraulics, vegetated flows, Flow-plant interactions, Drag model, drag coefficient

Received: 27 Aug 2018; Accepted: 08 Nov 2018.

Edited by:

Roshanka Ranasinghe, IHE Delft Institute for Water Education, Netherlands

Reviewed by:

Vanesa Magar, Ensenada Center for Scientific Research and Higher Education (CICESE), Mexico
Tomohiro Suzuki, Flanders Hydraulics Research, Belgium  

Copyright: © 2018 van Rooijen, Lowe, Ghisalberti, Conde-Frias and Tan. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mr. Arnold van Rooijen, School of Earth Sciences, Faculty of Science, University of Western Australia, Perth, 6009, Western Australia, Australia, aavrooijen@gmail.com