The University of Southampton
University of Southampton Institutional Repository
Warning ePrints Soton is experiencing an issue with some file downloads not being available. We are working hard to fix this. Please bear with us.

The role of salinity in fluvio-deltaic morphodynamics: a long-term modelling study

The role of salinity in fluvio-deltaic morphodynamics: a long-term modelling study
The role of salinity in fluvio-deltaic morphodynamics: a long-term modelling study
Salinity difference between terrestrial river discharge and oceanic tidal water plays a role in modifying the local flow field and, as a consequence, estuarine morphodynamics. Although widely recognized, recent numerical studies exploring the long-term morphological evolution of river-influenced estuaries with two-dimensional, depth-averaged models have mostly neglected salinity. Using a three-dimensional morphodynamic model, we aim to gain more insight into the effect of salinity on the morphodynamics of fluvio-deltaic systems. Model results indicate that the resultant estuarine morphology established after 600 years differs remarkably when a salinity gradient is included. A fan-shaped river-mouth delta exhibits less seaward expansion and is cut through by narrower channels when salinity is included. The inclusion of salinity tends to generate estuarine circulation, which favours landward sediment transport and hence limits the growth of the delta while enhancing the development of intertidal areas. The formation of deltaic channel–shoal patterns resulting from morphodynamic evolution tends to strengthen salinity stratification, which is characterized by an increased gradient Richardson number. The direction of the depth-averaged residual sediment transport over a tide may be opposite to the direction of residual velocity, indicating the significant influence of baroclinic effects on the net sediment transport direction (and hence morphological change). The effect of salinity on morphological evolution becomes less profound when the strength of tidal or fluvial forcing is dominant over the other. The effects of sediment type and flocculation, which are particularly important when salinity gradients are present, are also discussed. Overall, this study highlights that neglecting salinity to simulate long-term estuarine morphodynamics requires more careful justification, particularly when the environment is characterized by fine sediment types (favouring suspended transport), and relatively large river discharge and estuarine depth (favouring baroclinic effects).
baroclinic effect, estuarine morphodynamics, fluvio-deltaic systems, long-term morphodynamic modelling, salinity gradients
1674-2370
590-604
Zhou, Zeng
9679ce91-b86e-4355-901d-5a68abc50483
Chen, Luying
0b3e19dc-18de-4126-a62c-b6cd1d404585
Tao, Jianfeng
6cfe19e9-575c-4b61-8ed2-c6ea8b798fcf
Gong, Zheng
8fec227f-4dcc-431e-85c3-13a520574886
Guo, Leicheng
17e93f75-1537-481e-bba6-c9217b42428f
van der Wegen, Mick
d2a102db-0ab2-4563-a437-3f11f230d2c7
Townend, Ian
f72e5186-cae8-41fd-8712-d5746f78328e
Zhang, Changkuan
dfdb560e-6606-4ba2-86be-f7068ef48393
Zhou, Zeng
9679ce91-b86e-4355-901d-5a68abc50483
Chen, Luying
0b3e19dc-18de-4126-a62c-b6cd1d404585
Tao, Jianfeng
6cfe19e9-575c-4b61-8ed2-c6ea8b798fcf
Gong, Zheng
8fec227f-4dcc-431e-85c3-13a520574886
Guo, Leicheng
17e93f75-1537-481e-bba6-c9217b42428f
van der Wegen, Mick
d2a102db-0ab2-4563-a437-3f11f230d2c7
Townend, Ian
f72e5186-cae8-41fd-8712-d5746f78328e
Zhang, Changkuan
dfdb560e-6606-4ba2-86be-f7068ef48393

Zhou, Zeng, Chen, Luying, Tao, Jianfeng, Gong, Zheng, Guo, Leicheng, van der Wegen, Mick, Townend, Ian and Zhang, Changkuan (2020) The role of salinity in fluvio-deltaic morphodynamics: a long-term modelling study. Water Science and Engineering, 45 (3), 590-604. (doi:10.1002/esp.4757).

Record type: Article

Abstract

Salinity difference between terrestrial river discharge and oceanic tidal water plays a role in modifying the local flow field and, as a consequence, estuarine morphodynamics. Although widely recognized, recent numerical studies exploring the long-term morphological evolution of river-influenced estuaries with two-dimensional, depth-averaged models have mostly neglected salinity. Using a three-dimensional morphodynamic model, we aim to gain more insight into the effect of salinity on the morphodynamics of fluvio-deltaic systems. Model results indicate that the resultant estuarine morphology established after 600 years differs remarkably when a salinity gradient is included. A fan-shaped river-mouth delta exhibits less seaward expansion and is cut through by narrower channels when salinity is included. The inclusion of salinity tends to generate estuarine circulation, which favours landward sediment transport and hence limits the growth of the delta while enhancing the development of intertidal areas. The formation of deltaic channel–shoal patterns resulting from morphodynamic evolution tends to strengthen salinity stratification, which is characterized by an increased gradient Richardson number. The direction of the depth-averaged residual sediment transport over a tide may be opposite to the direction of residual velocity, indicating the significant influence of baroclinic effects on the net sediment transport direction (and hence morphological change). The effect of salinity on morphological evolution becomes less profound when the strength of tidal or fluvial forcing is dominant over the other. The effects of sediment type and flocculation, which are particularly important when salinity gradients are present, are also discussed. Overall, this study highlights that neglecting salinity to simulate long-term estuarine morphodynamics requires more careful justification, particularly when the environment is characterized by fine sediment types (favouring suspended transport), and relatively large river discharge and estuarine depth (favouring baroclinic effects).

Text
rv2_submitted - Accepted Manuscript
Download (6MB)
Text
Submitted manscript for 10.1002/esp.4757
Restricted to Repository staff only
Request a copy

More information

Accepted/In Press date: 23 October 2019
e-pub ahead of print date: 23 January 2020
Published date: 15 March 2020
Keywords: baroclinic effect, estuarine morphodynamics, fluvio-deltaic systems, long-term morphodynamic modelling, salinity gradients

Identifiers

Local EPrints ID: 437615
URI: http://eprints.soton.ac.uk/id/eprint/437615
ISSN: 1674-2370
PURE UUID: 26c0660b-1b22-463a-84e2-42fc159ae119
ORCID for Ian Townend: ORCID iD orcid.org/0000-0003-2101-3858

Catalogue record

Date deposited: 06 Feb 2020 17:32
Last modified: 26 Nov 2021 02:45

Export record

Altmetrics

Contributors

Author: Zeng Zhou
Author: Luying Chen
Author: Jianfeng Tao
Author: Zheng Gong
Author: Leicheng Guo
Author: Mick van der Wegen
Author: Ian Townend ORCID iD
Author: Changkuan Zhang

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×