Morphological evolution of a non-engineered managed realignment site following tidal inundation

Jonathan Dale, Heidi Burgess, Maureen Berg, Conor Strong, Niall Burnside

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There is growing evidence that managed realignment (MR) sites have lower biodiversity than natural saltmarshes, which has been associated with differences in the physical function and morphological evolution following site breaching. This evidence has been derived from MR sites previously used for intensive arable agriculture or modified during site construction. Therefore, the development of these sites may not be representative of the sedimentological evolution that would have otherwise occurred. This paper presents analysis of high spatial resolution digital surface models derived from the images collected using a small-unmanned aerial system from a non-engineered MR site at Cwm Ivy Marsh, Gower Peninsula, Wales. These models are examined alongside a novel combination of high frequency measurements of the rate and patterns of sedimentation, suspended sediment concentration (SSC), and the sub-surface structure and geochemical profiles. Results indicated that although the site became topographically less variable over a four year period, the intertidal morphology developed through an increase in the abundance of higher order creek systems and sediment being deposited at a rate of between 3 and 7 cm/year. The SSC followed an inverse pattern to water depth, with bed elevation increasing and then decreasing during both the flood and ebb tidal phases. Analysis of the sediment subsurface geochemical composition indicated redox profiles similar to natural intertidal environments; evidence of a fluctuating water table was found at a saltmarsh site, in comparison to waterlogging identified at an anoxic mudflat site. These findings provide a new insight to the sedimentological processes in a MR site without the influence of landscaping or site engineering prior to site breaching, which can be used to inform the design of future MR sites.

Original languageEnglish
Article number107510
Pages (from-to)1-11
JournalEstuarine, Coastal and Shelf Science
Publication statusPublished - 17 Jul 2021

Bibliographical note

Funding Information:
The authors would like to thank: Shari Gallop and two other anonymous reviewers for their detailed and supportive comments; Magda Grove and Matthew Leake (both University of Brighton ) for their assistance during field work; Corrinne Benbow (National Trust) and James Moon ( Natural Resources Wales ) for their support, guidance and for providing accommodation during field campaigns; Natural Resources Wales for granting access to previous survey data carried out by Future Aerial Innovations on behalf JBA Consulting. Financial support for this research was provided by Natural Resources Wales and the School of Environment and Technology, University of Brighton.


  • sedimentation rate
  • coastal geomorphology
  • coastal wetlands
  • Small-Unmanned Aerial System (sUAS)
  • Sedimentation rates
  • Coastal wetlands: small-unmanned aerial system
  • Coastal geomorphology


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