Kenneth Pye Associates Ltd.
 Scientific Research, Consultancy and Investigations

              
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Intertidal habitat development on managed retreat sites in Essex, UK
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Project funded by the Department for Environment, Food and Rural Affairs as part of the Estuaries Research Programme (ERP) Uptake Project

Managed retreat is increasingly seen as an important way of reducing coastal squeeze and creating areas of intertidal habitat within a framework of sustainable flood defence management. Several schemes have been established in England and Wales in recent years, including four in the Blackwater estuary, Essex.  The most recent was activated in October 2002 at Abbotts Hall on the north side of  Salcott Creek. The original scheme involved five breaches of the sea wall, creating approximately 20 ha of intertidal habitat.

                            Elevation (m OD)                                                        Lidar image of Salcott Creek
  

A key question in designing any managed retreat site concerns the nature of the habitats which will be created, and their likely long-term development. Studies of historical sea wall failures in Essex have shown that former reclaimed areas may respond to renewed tidal flooding in different ways depending on a number of factors, most importantly the elevation of the land at the time of breach, which governs the frequency and duration of tidal flooding.

In this study, digital terrain modelling was conducted using airborne lidar data.  This data was used to calculate the elevation of the land behind a breach and to predict the likely habitats which will be created.

Bathymetric maps showing one of the breached areas in Salcott Creek. Top left: bathymetric map of the area behind the sea walls before breaching. Top right: model of tidal inundation at mean high water springs after breaching of the sea wall  (inundated areas shown in blue). Bottom left: Predictions of the likely habitats which will be created, based on the elevation of the land in relation to the tidal frame.

Using data from sites of historical sea wall failure in Essex, predictions can be made of the likely evolution of the created habitats in the longer term. At Abbotts Hall, the highest areas above 2.35 m OD are predicted to develop stable saltmarsh, intermediate areas between 2.1 and 2.34 m OD to develop potentially unstable saltmarsh which may undergo internal dissection, and the lowest areas below 2.1 m OD are likely to remain as mudflat or lagoon.  Approximately 38 percent of the combined site is predicted to develop stable saltmarsh, and nearly 50 percent to remain as lagoon or mudflat.

Publications and Reports

Blott, S.J. and Pye, K. (2004) Application of lidar digital terrain modelling to predict intertidal habitat development at a managed retreat site: Abbotts Hall, Essex, UK. Earth Surface Processes and Landforms 29, 893-905.
(click to view the abstract of this paper)

Pye, K. and Blott, S.J. (2002). Saltmarsh Development at Salcott Managed Retreat Site, Essex, UK. SPME, Royal Holloway, University of London, Research Report CS13, 29 pp.

Kenneth Pye Associates Ltd. - Environmental Consultants
Page last modified: July 11, 2007