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Sediment transport over an accretional intertidal flat with influences of reclamation, Jiangsu coast, China

Sediment transport over an accretional intertidal flat with influences of reclamation, Jiangsu coast, China
Sediment transport over an accretional intertidal flat with influences of reclamation, Jiangsu coast, China
This paper focuses on the hydrodynamic and suspended sediment transport processes in response to sequential reclamations over the intertidal flat, Jiangsu coast, which used to be one of the widest intertidal flats in China. Investigations into the sediment transport patterns reveal that net suspended sediment fluxes increased from 102 kg m?1 on the upper intertidal flat to 103–4 kg m?1 on the lower intertidal flat, per tidal cycle. This variation was caused mainly by the phases of the current velocity, suspended sediment concentration (SSC), local bed geomorphology, inundation patterns, and extreme weather conditions. The longshore component of tidal currents intensifies seaward over the intertidal flat. Extreme weather conditions (e.g. storms) and strong winds were important factors affecting the current velocity structures, the intensity of residual currents, and the SSCs. The SSCs were characterized by several peaks throughout the tidal cycle. These peaks were associated with strong currents, combined wave-current interactions and intense turbulences due to the initial flood surge. Furthermore, the suspended sediment was finer and contained more clay materials during the flood phase of the tidal cycle, than during the ebb. Fine particles were transported within the upper water column by landward residual currents, but coarse particles were transported within the lower water column by seaward residual currents. Overall, residual currents were apt to transport fine-grained sediment landward and coarse-grained sediment seaward. This pattern indicates that the suspended sediment fluxes are highly variable in the water column, even for very shallow tidal environments. The cross-shore component accounted only for a small percentage of the total sediment flux. However, this part of sediment supply dominated accretion over the intertidal flat.

The intertidal flat has become narrower and steeper, following sequential reclamations. A negative feedback process existed to maintain the convex profile shape, although the human activities (i.e. reclamation) could have modified the natural process. The surficial sediment tended to become finer on the mid-upper intertidal flat but coarser on the lower intertidal flat following reclamations, in response to a reduction in the tidal currents over the intertidal zone and enhancement of wave action over the lower intertidal flat. Accretion, with high rates, was maintained by landward transport of sediment. In such an accretional system with influences of reclamation, the width or slope of the intertidal flat is adjusted continuously. Before the cease of reclamation, the intertidal flat is unable to achieve an equilibrium shape.
current-wave interactions, suspended sediment concentrations, intertidal flats, reclamation, Jiangsu coast
0025-3227
147-161
Wang, Ya Ping
39ca2e13-2d50-4fef-9258-f0c1a1f7681b
Gao, Shu
467252e2-525c-4729-8e99-b98cde7ee1d9
Jia, Jianjun
522e1897-347b-45e0-b4a4-08f76a96754d
Thompson, Charlotte E.L.
2a304aa6-761e-4d99-b227-cedb67129bfb
Gao, Jianhua
5cf171d3-075d-4d7c-80e7-c3ce512cc5d1
Yang, Yang
d1e03c97-703a-4139-bb00-6db4be624188
Wang, Ya Ping
39ca2e13-2d50-4fef-9258-f0c1a1f7681b
Gao, Shu
467252e2-525c-4729-8e99-b98cde7ee1d9
Jia, Jianjun
522e1897-347b-45e0-b4a4-08f76a96754d
Thompson, Charlotte E.L.
2a304aa6-761e-4d99-b227-cedb67129bfb
Gao, Jianhua
5cf171d3-075d-4d7c-80e7-c3ce512cc5d1
Yang, Yang
d1e03c97-703a-4139-bb00-6db4be624188

Wang, Ya Ping, Gao, Shu, Jia, Jianjun, Thompson, Charlotte E.L., Gao, Jianhua and Yang, Yang (2012) Sediment transport over an accretional intertidal flat with influences of reclamation, Jiangsu coast, China. Marine Geology, 291-294, 147-161. (doi:10.1016/j.margeo.2011.01.004).

Record type: Article

Abstract

This paper focuses on the hydrodynamic and suspended sediment transport processes in response to sequential reclamations over the intertidal flat, Jiangsu coast, which used to be one of the widest intertidal flats in China. Investigations into the sediment transport patterns reveal that net suspended sediment fluxes increased from 102 kg m?1 on the upper intertidal flat to 103–4 kg m?1 on the lower intertidal flat, per tidal cycle. This variation was caused mainly by the phases of the current velocity, suspended sediment concentration (SSC), local bed geomorphology, inundation patterns, and extreme weather conditions. The longshore component of tidal currents intensifies seaward over the intertidal flat. Extreme weather conditions (e.g. storms) and strong winds were important factors affecting the current velocity structures, the intensity of residual currents, and the SSCs. The SSCs were characterized by several peaks throughout the tidal cycle. These peaks were associated with strong currents, combined wave-current interactions and intense turbulences due to the initial flood surge. Furthermore, the suspended sediment was finer and contained more clay materials during the flood phase of the tidal cycle, than during the ebb. Fine particles were transported within the upper water column by landward residual currents, but coarse particles were transported within the lower water column by seaward residual currents. Overall, residual currents were apt to transport fine-grained sediment landward and coarse-grained sediment seaward. This pattern indicates that the suspended sediment fluxes are highly variable in the water column, even for very shallow tidal environments. The cross-shore component accounted only for a small percentage of the total sediment flux. However, this part of sediment supply dominated accretion over the intertidal flat.

The intertidal flat has become narrower and steeper, following sequential reclamations. A negative feedback process existed to maintain the convex profile shape, although the human activities (i.e. reclamation) could have modified the natural process. The surficial sediment tended to become finer on the mid-upper intertidal flat but coarser on the lower intertidal flat following reclamations, in response to a reduction in the tidal currents over the intertidal zone and enhancement of wave action over the lower intertidal flat. Accretion, with high rates, was maintained by landward transport of sediment. In such an accretional system with influences of reclamation, the width or slope of the intertidal flat is adjusted continuously. Before the cease of reclamation, the intertidal flat is unable to achieve an equilibrium shape.

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More information

Published date: 2012
Keywords: current-wave interactions, suspended sediment concentrations, intertidal flats, reclamation, Jiangsu coast
Organisations: Coastal & Shelf Research

Identifiers

Local EPrints ID: 338074
URI: http://eprints.soton.ac.uk/id/eprint/338074
ISSN: 0025-3227
PURE UUID: 2d276f15-f4bf-4d3e-acf8-0bb9e5a247e6
ORCID for Charlotte E.L. Thompson: ORCID iD orcid.org/0000-0003-1105-6838

Catalogue record

Date deposited: 08 May 2012 15:31
Last modified: 15 Mar 2024 03:05

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Contributors

Author: Ya Ping Wang
Author: Shu Gao
Author: Jianjun Jia
Author: Jianhua Gao
Author: Yang Yang

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