Hydrodynamics and sedimentary processes in the main drainage channel of a large open coast managed realignment site

Jonathan Dale, Heidi M. Burgess, David J. Nash, Andrew B. Cundy

Research output: Contribution to journalArticle

2 Citations (Scopus)
3 Downloads (Pure)

Abstract

Managed Realignment (MR) is becoming increasingly popular with many coastal managers and engineers. Monitoring of MR sites has provided growing evidence that many of the saltmarshes created in these environments have lower biodiversity than naturally formed intertidal marshes, and may not fully deliver the anticipated ecosystem services such as carbon sequestration and coastal flood defence. Despite the importance of the sedimentary environment in developing an intertidal morphology suitable for plant establishment and succession, the evolution of the sediment erosion, transportation, deposition and consolidation cycle in newly breached sites is rarely examined. This study evaluates the hydrodynamics and concentration of suspended sediment exported and imported along the main drainage channel within the Medmerry Managed Realignment Site, West Sussex, UK, the largest open coast realignment in Europe (at the time of breaching). Measurements were taken over a one year period (November 2015–October 2016) at the breach, at the landwards extremity where freshwater drains into the site, and in an excavated channel in the centre of the site. At the latter site, 1.7 cm of sediment accreted over the study period. Suspended sediment concentration (SSC) measurements indicate that, under ambient conditions, sediment is imported into and exported from the Medmerry site, although similar concentrations of sediment were recorded being internally redistributed around the site (typically 0.11 g/l measured in the breach area compared to 0.12 g/l measured in the centre of the site). Sediment is removed from the site following large (1–2 mm/hour) rainfall events, which take several tidal cycles to drain through the site. Peaks in SSC corresponding with lower intensity rainfall events, especially during periods when the intertidal mudflats have been exposed, have also been observed. Analysis of the hydrodynamics and patterns of sedimentation during and following storm occurrences (the 2015-16 Storms Eva, Imogen and Katie) however demonstrate the relative resilience (i.e. rapid recovery and minimal disturbance) of the site to extreme storm events.

Original languageEnglish
Pages (from-to)100-111
Number of pages12
JournalEstuarine, Coastal and Shelf Science
Volume215
Early online date16 Oct 2018
DOIs
Publication statusPublished - 31 Dec 2018
Externally publishedYes

Fingerprint

managed realignment
drainage channels
hydrodynamics
drainage
coasts
sediments
coast
suspended sediment
sediment
drain
ecological succession
rain intensity
plant establishment
tidal cycle
mudflat
precipitation intensity
salt marshes
engineers
carbon sequestration
ecosystem service

Bibliographical note

NOTICE: this is the author’s version of a work that was accepted for publication in Estuarine, Coastal and Shelf Science. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Estuarine, Coastal and Shelf Science, [[215], (2018)] DOI: 10.1016/j.ecss.2018.10.007

© 2017, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/

Keywords

  • Altimeter
  • Hydrodynamics
  • Managed realignment
  • Medmerry managed realignment site
  • Storms
  • Suspended sediment concentration
  • United Kingdom
  • West sussex

ASJC Scopus subject areas

  • Oceanography
  • Aquatic Science

Cite this

Hydrodynamics and sedimentary processes in the main drainage channel of a large open coast managed realignment site. / Dale, Jonathan; Burgess, Heidi M.; Nash, David J.; Cundy, Andrew B.

In: Estuarine, Coastal and Shelf Science, Vol. 215, 31.12.2018, p. 100-111.

Research output: Contribution to journalArticle

@article{1ec1bb771e81486db9880417f507b244,
title = "Hydrodynamics and sedimentary processes in the main drainage channel of a large open coast managed realignment site",
abstract = "Managed Realignment (MR) is becoming increasingly popular with many coastal managers and engineers. Monitoring of MR sites has provided growing evidence that many of the saltmarshes created in these environments have lower biodiversity than naturally formed intertidal marshes, and may not fully deliver the anticipated ecosystem services such as carbon sequestration and coastal flood defence. Despite the importance of the sedimentary environment in developing an intertidal morphology suitable for plant establishment and succession, the evolution of the sediment erosion, transportation, deposition and consolidation cycle in newly breached sites is rarely examined. This study evaluates the hydrodynamics and concentration of suspended sediment exported and imported along the main drainage channel within the Medmerry Managed Realignment Site, West Sussex, UK, the largest open coast realignment in Europe (at the time of breaching). Measurements were taken over a one year period (November 2015–October 2016) at the breach, at the landwards extremity where freshwater drains into the site, and in an excavated channel in the centre of the site. At the latter site, 1.7 cm of sediment accreted over the study period. Suspended sediment concentration (SSC) measurements indicate that, under ambient conditions, sediment is imported into and exported from the Medmerry site, although similar concentrations of sediment were recorded being internally redistributed around the site (typically 0.11 g/l measured in the breach area compared to 0.12 g/l measured in the centre of the site). Sediment is removed from the site following large (1–2 mm/hour) rainfall events, which take several tidal cycles to drain through the site. Peaks in SSC corresponding with lower intensity rainfall events, especially during periods when the intertidal mudflats have been exposed, have also been observed. Analysis of the hydrodynamics and patterns of sedimentation during and following storm occurrences (the 2015-16 Storms Eva, Imogen and Katie) however demonstrate the relative resilience (i.e. rapid recovery and minimal disturbance) of the site to extreme storm events.",
keywords = "Altimeter, Hydrodynamics, Managed realignment, Medmerry managed realignment site, Storms, Suspended sediment concentration, United Kingdom, West sussex",
author = "Jonathan Dale and Burgess, {Heidi M.} and Nash, {David J.} and Cundy, {Andrew B.}",
note = "NOTICE: this is the author’s version of a work that was accepted for publication in Estuarine, Coastal and Shelf Science. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Estuarine, Coastal and Shelf Science, [[215], (2018)] DOI: 10.1016/j.ecss.2018.10.007 {\circledC} 2017, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/",
year = "2018",
month = "12",
day = "31",
doi = "10.1016/j.ecss.2018.10.007",
language = "English",
volume = "215",
pages = "100--111",
journal = "Estuarine, Coastal and Shelf Science",
issn = "0272-7714",
publisher = "Elsevier",

}

TY - JOUR

T1 - Hydrodynamics and sedimentary processes in the main drainage channel of a large open coast managed realignment site

AU - Dale, Jonathan

AU - Burgess, Heidi M.

AU - Nash, David J.

AU - Cundy, Andrew B.

N1 - NOTICE: this is the author’s version of a work that was accepted for publication in Estuarine, Coastal and Shelf Science. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Estuarine, Coastal and Shelf Science, [[215], (2018)] DOI: 10.1016/j.ecss.2018.10.007 © 2017, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/

PY - 2018/12/31

Y1 - 2018/12/31

N2 - Managed Realignment (MR) is becoming increasingly popular with many coastal managers and engineers. Monitoring of MR sites has provided growing evidence that many of the saltmarshes created in these environments have lower biodiversity than naturally formed intertidal marshes, and may not fully deliver the anticipated ecosystem services such as carbon sequestration and coastal flood defence. Despite the importance of the sedimentary environment in developing an intertidal morphology suitable for plant establishment and succession, the evolution of the sediment erosion, transportation, deposition and consolidation cycle in newly breached sites is rarely examined. This study evaluates the hydrodynamics and concentration of suspended sediment exported and imported along the main drainage channel within the Medmerry Managed Realignment Site, West Sussex, UK, the largest open coast realignment in Europe (at the time of breaching). Measurements were taken over a one year period (November 2015–October 2016) at the breach, at the landwards extremity where freshwater drains into the site, and in an excavated channel in the centre of the site. At the latter site, 1.7 cm of sediment accreted over the study period. Suspended sediment concentration (SSC) measurements indicate that, under ambient conditions, sediment is imported into and exported from the Medmerry site, although similar concentrations of sediment were recorded being internally redistributed around the site (typically 0.11 g/l measured in the breach area compared to 0.12 g/l measured in the centre of the site). Sediment is removed from the site following large (1–2 mm/hour) rainfall events, which take several tidal cycles to drain through the site. Peaks in SSC corresponding with lower intensity rainfall events, especially during periods when the intertidal mudflats have been exposed, have also been observed. Analysis of the hydrodynamics and patterns of sedimentation during and following storm occurrences (the 2015-16 Storms Eva, Imogen and Katie) however demonstrate the relative resilience (i.e. rapid recovery and minimal disturbance) of the site to extreme storm events.

AB - Managed Realignment (MR) is becoming increasingly popular with many coastal managers and engineers. Monitoring of MR sites has provided growing evidence that many of the saltmarshes created in these environments have lower biodiversity than naturally formed intertidal marshes, and may not fully deliver the anticipated ecosystem services such as carbon sequestration and coastal flood defence. Despite the importance of the sedimentary environment in developing an intertidal morphology suitable for plant establishment and succession, the evolution of the sediment erosion, transportation, deposition and consolidation cycle in newly breached sites is rarely examined. This study evaluates the hydrodynamics and concentration of suspended sediment exported and imported along the main drainage channel within the Medmerry Managed Realignment Site, West Sussex, UK, the largest open coast realignment in Europe (at the time of breaching). Measurements were taken over a one year period (November 2015–October 2016) at the breach, at the landwards extremity where freshwater drains into the site, and in an excavated channel in the centre of the site. At the latter site, 1.7 cm of sediment accreted over the study period. Suspended sediment concentration (SSC) measurements indicate that, under ambient conditions, sediment is imported into and exported from the Medmerry site, although similar concentrations of sediment were recorded being internally redistributed around the site (typically 0.11 g/l measured in the breach area compared to 0.12 g/l measured in the centre of the site). Sediment is removed from the site following large (1–2 mm/hour) rainfall events, which take several tidal cycles to drain through the site. Peaks in SSC corresponding with lower intensity rainfall events, especially during periods when the intertidal mudflats have been exposed, have also been observed. Analysis of the hydrodynamics and patterns of sedimentation during and following storm occurrences (the 2015-16 Storms Eva, Imogen and Katie) however demonstrate the relative resilience (i.e. rapid recovery and minimal disturbance) of the site to extreme storm events.

KW - Altimeter

KW - Hydrodynamics

KW - Managed realignment

KW - Medmerry managed realignment site

KW - Storms

KW - Suspended sediment concentration

KW - United Kingdom

KW - West sussex

UR - http://www.scopus.com/inward/record.url?scp=85055350288&partnerID=8YFLogxK

U2 - 10.1016/j.ecss.2018.10.007

DO - 10.1016/j.ecss.2018.10.007

M3 - Article

VL - 215

SP - 100

EP - 111

JO - Estuarine, Coastal and Shelf Science

JF - Estuarine, Coastal and Shelf Science

SN - 0272-7714

ER -