A comparison of biohydrodynamic interaction within mangrove and saltmarsh boundaries
A comparison of biohydrodynamic interaction within mangrove and saltmarsh boundaries
Mangrove forests and saltmarshes are recognized for their roles in wave and current attenuation, although a comparison of in situ observations between woody and herbaceous plants is needed in order to understand the different mechanisms of bio-physical interaction within coastal wetlands. The aim of our study was to compare the mechanisms of flow reduction and energy dissipation by mangrove trees and saltmarsh grass in a subtropical area where tidal currents dominate. Fieldwork was conducted to measure the hydrodynamic processes occurring at the boundaries between a bare mudflat and vegetated tidal flat, as the flow transitions from a bare mudflat to either mangrove or saltmarsh. Synchronous ADV measurements at three sites revealed that the mangrove was more effective than the saltmarsh grass at flow reduction. In addition, a considerable rotation in flow direction was observed as the flow entered the mangrove trees, while rotation was considerably less pronounced within the saltmarsh edge. The mechanism for this difference was explained through a combination of changes in drag force and eddy viscosity over the two vegetation types. Although overall the mangrove was observed to dissipate energy more effectively than the saltmarsh, the relative efficiency of the vegetation at dissipating turbulent energy was found to vary with the maximum water level of tidal cycle. When the maximum water level remained below the mangrove canopy bottom (‘bio-line’), the energy dissipation ability of the mangrove was relatively low, a result of the presence of rigid, sparse trunks rather than denser saltmarsh grass found near the bed; when the maximum water level was sufficiently high to reach the mangrove canopy, the ability of the mangrove to dissipate energy was significantly increased, becoming more effective than the saltmarsh grass.
Mangrove, Saltmarsh, Hydrodynamics, Vegetation Drag
1967-1979
Chen, Yining
9bd0c98e-117f-4e81-b9cf-49a621abb63c
Li, Yan
d4b90b76-cde3-4166-9b65-36130e424d83
Cai, Tinglu
229971fd-173f-41ca-bfb5-62b884b41317
Thompson, Charlotte
2a304aa6-761e-4d99-b227-cedb67129bfb
Li, Yi
76dfac3c-5e81-4b4e-8887-98e9d91dd119
6 October 2016
Chen, Yining
9bd0c98e-117f-4e81-b9cf-49a621abb63c
Li, Yan
d4b90b76-cde3-4166-9b65-36130e424d83
Cai, Tinglu
229971fd-173f-41ca-bfb5-62b884b41317
Thompson, Charlotte
2a304aa6-761e-4d99-b227-cedb67129bfb
Li, Yi
76dfac3c-5e81-4b4e-8887-98e9d91dd119
Chen, Yining, Li, Yan, Cai, Tinglu, Thompson, Charlotte and Li, Yi
(2016)
A comparison of biohydrodynamic interaction within mangrove and saltmarsh boundaries.
Earth Surface Processes and Landforms, 41 (13), .
(doi:10.1002/esp.3964).
Abstract
Mangrove forests and saltmarshes are recognized for their roles in wave and current attenuation, although a comparison of in situ observations between woody and herbaceous plants is needed in order to understand the different mechanisms of bio-physical interaction within coastal wetlands. The aim of our study was to compare the mechanisms of flow reduction and energy dissipation by mangrove trees and saltmarsh grass in a subtropical area where tidal currents dominate. Fieldwork was conducted to measure the hydrodynamic processes occurring at the boundaries between a bare mudflat and vegetated tidal flat, as the flow transitions from a bare mudflat to either mangrove or saltmarsh. Synchronous ADV measurements at three sites revealed that the mangrove was more effective than the saltmarsh grass at flow reduction. In addition, a considerable rotation in flow direction was observed as the flow entered the mangrove trees, while rotation was considerably less pronounced within the saltmarsh edge. The mechanism for this difference was explained through a combination of changes in drag force and eddy viscosity over the two vegetation types. Although overall the mangrove was observed to dissipate energy more effectively than the saltmarsh, the relative efficiency of the vegetation at dissipating turbulent energy was found to vary with the maximum water level of tidal cycle. When the maximum water level remained below the mangrove canopy bottom (‘bio-line’), the energy dissipation ability of the mangrove was relatively low, a result of the presence of rigid, sparse trunks rather than denser saltmarsh grass found near the bed; when the maximum water level was sufficiently high to reach the mangrove canopy, the ability of the mangrove to dissipate energy was significantly increased, becoming more effective than the saltmarsh grass.
Text
Chen et al ESPL_accepted.pdf
- Accepted Manuscript
More information
Accepted/In Press date: 25 April 2016
e-pub ahead of print date: 2 June 2016
Published date: 6 October 2016
Keywords:
Mangrove, Saltmarsh, Hydrodynamics, Vegetation Drag
Organisations:
Coastal & Shelf Research
Identifiers
Local EPrints ID: 393685
URI: http://eprints.soton.ac.uk/id/eprint/393685
ISSN: 0197-9337
PURE UUID: 1c746a98-ef9d-46fc-b054-4b4f6330f61f
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Date deposited: 09 May 2016 16:08
Last modified: 15 Mar 2024 05:32
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Author:
Yining Chen
Author:
Yan Li
Author:
Tinglu Cai
Author:
Yi Li
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