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Differential sediment trapping abilities of mangrove and saltmarsh vegetation a subtropical estuary

Differential sediment trapping abilities of mangrove and saltmarsh vegetation a subtropical estuary
Differential sediment trapping abilities of mangrove and saltmarsh vegetation a subtropical estuary
Saltmarsh and mangrove are common coastal wetland types and their ability to enhance deposition has been investigated extensively, but rarely compared directly. This study carried out in situ observations to compare the sediment transport processes between a bare mudflat, a mangrove stand and a saltmarsh stand within a subtropical estuary. Turbidity variations over the latter portion of a spring tide were recorded, alongside measurements of flow data, to estimate sediment trapping by hydraulic forces under similar hydroperiods. In addition, vegetation was transplanted to compare the direct sediment trapping by high- and short-standing seedlings. The suspended sediment concentration (SSC) time series showed an overall reduction between the bare mudflat and the vegetated flats. Suspended sediment flux estimates revealed that a considerable amount of sediment was trapped by the saltmarsh and the mangrove edges. The flux estimates find that the saltmarsh edge is more efficient than the mangrove edge in trapping sediments transported normal to the edge. The sediment trapping mechanisms were considered based on two approaches: the hydrodynamic related sediment settling and direct trapping by vegetation. The calculation of deposition tendency showed that the presence of vegetation altered the flow direction and the tidal asymmetry of the deposition process, resulting in a higher deposition tendency during the flood phase to enhance sediment settling. In addition to sediment settling, vegetation surfaces were found to trap sediments directly. In combination with rinsing by precipitation, these trapped sediments accumulated on the bed and contributed to the deposition. Against the background of similar inundation periods, the saltmarsh grass showed a greater sediment trapping ability than the mangrove trees, in terms of both the hydraulic sediment trapping and the direct trapping by vegetation surface.
0169-555X
270-282
Chen, Yining
9bd0c98e-117f-4e81-b9cf-49a621abb63c
Li, Yan
c1e2518d-f89d-404f-9a82-27046e844764
Thompson, Charlotte
2a304aa6-761e-4d99-b227-cedb67129bfb
Wang, Xinkai
8fe408e5-e739-496c-8a19-0c2af75d3af1
Cai, Tinglu
229971fd-173f-41ca-bfb5-62b884b41317
Chang, Yang
38cabd15-4c96-4fbc-8790-92354fe29978
Chen, Yining
9bd0c98e-117f-4e81-b9cf-49a621abb63c
Li, Yan
c1e2518d-f89d-404f-9a82-27046e844764
Thompson, Charlotte
2a304aa6-761e-4d99-b227-cedb67129bfb
Wang, Xinkai
8fe408e5-e739-496c-8a19-0c2af75d3af1
Cai, Tinglu
229971fd-173f-41ca-bfb5-62b884b41317
Chang, Yang
38cabd15-4c96-4fbc-8790-92354fe29978

Chen, Yining, Li, Yan, Thompson, Charlotte, Wang, Xinkai, Cai, Tinglu and Chang, Yang (2018) Differential sediment trapping abilities of mangrove and saltmarsh vegetation a subtropical estuary. Geomorphology, 318, 270-282. (doi:10.1016/j.geomorph.2018.06.018).

Record type: Article

Abstract

Saltmarsh and mangrove are common coastal wetland types and their ability to enhance deposition has been investigated extensively, but rarely compared directly. This study carried out in situ observations to compare the sediment transport processes between a bare mudflat, a mangrove stand and a saltmarsh stand within a subtropical estuary. Turbidity variations over the latter portion of a spring tide were recorded, alongside measurements of flow data, to estimate sediment trapping by hydraulic forces under similar hydroperiods. In addition, vegetation was transplanted to compare the direct sediment trapping by high- and short-standing seedlings. The suspended sediment concentration (SSC) time series showed an overall reduction between the bare mudflat and the vegetated flats. Suspended sediment flux estimates revealed that a considerable amount of sediment was trapped by the saltmarsh and the mangrove edges. The flux estimates find that the saltmarsh edge is more efficient than the mangrove edge in trapping sediments transported normal to the edge. The sediment trapping mechanisms were considered based on two approaches: the hydrodynamic related sediment settling and direct trapping by vegetation. The calculation of deposition tendency showed that the presence of vegetation altered the flow direction and the tidal asymmetry of the deposition process, resulting in a higher deposition tendency during the flood phase to enhance sediment settling. In addition to sediment settling, vegetation surfaces were found to trap sediments directly. In combination with rinsing by precipitation, these trapped sediments accumulated on the bed and contributed to the deposition. Against the background of similar inundation periods, the saltmarsh grass showed a greater sediment trapping ability than the mangrove trees, in terms of both the hydraulic sediment trapping and the direct trapping by vegetation surface.

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GEOMOR-7016R2 (1) - Accepted Manuscript
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Accepted/In Press date: 25 June 2018
e-pub ahead of print date: 28 June 2018
Published date: 1 October 2018

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Local EPrints ID: 422058
URI: http://eprints.soton.ac.uk/id/eprint/422058
ISSN: 0169-555X
PURE UUID: bba88fc0-d5bc-48a2-963f-8d2a67b41f4a

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Date deposited: 13 Jul 2018 16:30
Last modified: 07 Oct 2020 05:53

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