Sediment structure and physicochemical changes following tidal inundation at a large open coast managed realignment site

Jonathan Dale, Andrew Cundy, Kate L. Spencer, Simon J. Carr, Ian Croudace, Heidi Burgess, David Nash

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Managed realignment (MR) schemes are being implemented to compensate for the loss of intertidal saltmarsh habitats by breaching flood defences and inundating the formerly defended coastal hinterland. However, studies have shown that MR sites have lower biodiversity than anticipated, which has been linked with anoxia and poor drainage resulting from compaction and the collapse of sediment pore space caused by the site’s former terrestrial land use. Despite this proposed link between biodiversity and soil structure, the evolution of the sediment sub-surface following site inundation has rarely been examined, particularly over the early stages of the terrestrial to marine or estuarine transition. This paper presents a novel combination of broad- and intensive-scale analysis of the sub-surface evolution of the Medmerry Managed Realignment Site (West Sussex, UK) in the three years following site inundation. Repeated broad-scale sediment physiochemical datasets are analysed to assess the early changes in the sediment subsurface and the preservation of the former terrestrial surface, comparing four locations of different former land uses. Additionally, for two of these locations, high-intensity 3D-computed X-ray microtomography and Itrax micro-X-ray fluorescence spectrometry analyses are presented. Results provide new data on differences in sediment properties and structure related to the former land use, indicating that increased agricultural activity leads to increased compaction and reduced porosity. The presence of anoxic conditions, indicative of poor hydrological connectivity between the terrestrial and post-inundation intertidal sediment facies, was only detected at one site. This site has experienced the highest rate of accretion over the terrestrial surface (ca. 7 cm over 36 months), suggesting that poor drainage is caused by the interaction (or lack of) between sediment facies rather than the former land use. This has significant implications for the design of future MR sites in terms of preparing sites, their anticipated evolution, and the delivery of ecosystem services.
Original languageEnglish
Pages (from-to)1419-1432
Number of pages14
JournalScience of the Total Environment
Volume660
DOIs
Publication statusPublished - 28 Dec 2018

Fingerprint

managed realignment
Coastal zones
Sediments
coast
Land use
sediment
land use
Biodiversity
compaction
Drainage
biodiversity
drainage
Compaction
sediment property
anoxia
pore space
soil structure
X-ray fluorescence
ecosystem service
saltmarsh

Keywords

  • Managed Realignment
  • Microtomography
  • Sediment structure
  • Saltmarsh geochemistry
  • Itrax XRF

Cite this

Dale, Jonathan ; Cundy, Andrew ; Spencer, Kate L. ; Carr, Simon J. ; Croudace, Ian ; Burgess, Heidi ; Nash, David. / Sediment structure and physicochemical changes following tidal inundation at a large open coast managed realignment site. In: Science of the Total Environment. 2018 ; Vol. 660. pp. 1419-1432.
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abstract = "Managed realignment (MR) schemes are being implemented to compensate for the loss of intertidal saltmarsh habitats by breaching flood defences and inundating the formerly defended coastal hinterland. However, studies have shown that MR sites have lower biodiversity than anticipated, which has been linked with anoxia and poor drainage resulting from compaction and the collapse of sediment pore space caused by the site’s former terrestrial land use. Despite this proposed link between biodiversity and soil structure, the evolution of the sediment sub-surface following site inundation has rarely been examined, particularly over the early stages of the terrestrial to marine or estuarine transition. This paper presents a novel combination of broad- and intensive-scale analysis of the sub-surface evolution of the Medmerry Managed Realignment Site (West Sussex, UK) in the three years following site inundation. Repeated broad-scale sediment physiochemical datasets are analysed to assess the early changes in the sediment subsurface and the preservation of the former terrestrial surface, comparing four locations of different former land uses. Additionally, for two of these locations, high-intensity 3D-computed X-ray microtomography and Itrax micro-X-ray fluorescence spectrometry analyses are presented. Results provide new data on differences in sediment properties and structure related to the former land use, indicating that increased agricultural activity leads to increased compaction and reduced porosity. The presence of anoxic conditions, indicative of poor hydrological connectivity between the terrestrial and post-inundation intertidal sediment facies, was only detected at one site. This site has experienced the highest rate of accretion over the terrestrial surface (ca. 7 cm over 36 months), suggesting that poor drainage is caused by the interaction (or lack of) between sediment facies rather than the former land use. This has significant implications for the design of future MR sites in terms of preparing sites, their anticipated evolution, and the delivery of ecosystem services.",
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Sediment structure and physicochemical changes following tidal inundation at a large open coast managed realignment site. / Dale, Jonathan; Cundy, Andrew; Spencer, Kate L.; Carr, Simon J.; Croudace, Ian; Burgess, Heidi; Nash, David.

In: Science of the Total Environment, Vol. 660, 28.12.2018, p. 1419-1432.

Research output: Contribution to journalArticleResearchpeer-review

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T1 - Sediment structure and physicochemical changes following tidal inundation at a large open coast managed realignment site

AU - Dale, Jonathan

AU - Cundy, Andrew

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AU - Carr, Simon J.

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AU - Burgess, Heidi

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KW - Managed Realignment

KW - Microtomography

KW - Sediment structure

KW - Saltmarsh geochemistry

KW - Itrax XRF

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