Jubilee Marsh (Wallasea)

Year Implemented

2015

Project Type

Managed realignment

Country

United Kingdom

Location

Roach Estuary

Longitude

0.859

Latitude

51.6046

Habitat(s) Created
  • Mudflat

  • Saltmarsh

  • Transitional Grassland

  • Supralittoral terrestrial

Size

165 Hectares

Why Undertaken
Project Description Summary

'Wallasea Island Wild Coast' is an RSPB flagship project and the most ambitious marine wetland restoration in Europe. It involved implementing a phased sequence of managed realignments on Wallasea Island at the confluence of the Crouch and Roach Estuaries (Essex). This was done to achieve flood protection objectives and to return the island back to being a mosaic of mudflat marshes and lagoons - as it had once been in the 14th Century. The whole of Wallasea Island is around 800 ha (2,000 acre) and had sunk in elevation after several hundred years of progressive land claim and human intervention. As a result it had become 1.5m lower than a surrounding mean spring tide and, in this condition, there was a severe risk of tidal waters overtopping and breaking through the sea walls. If this future flood was just allowed to occur, it would have done so very rapidly and in such a large volume (11 million m3 - equating to 67% of the Roach Estuary tidal prism) that it would have caused significant, and potentially irreversible, changes to the estuary flow regime (affecting flood protection, water quality and oyster fisheries in the estuary). To address this critical flood defence need (and to restore vulnerable coastal habitat), a range of innovative and sustainable long-term solutions were developed. For Phase 1 (also called Cell 1 or Jubilee Marsh) the solution involved raising the island's landform using 1.65 million m3 of landscaping material from the London Crossrail project. Once completed, the tidal exchange for Jubilee Marsh alone was reduced to 1.2 million m3. This first phase was completed in July 2015 (in partnership with Crossrail and the UK's Environment Agency). Jubilee Marsh is 165 ha (407 acre) in size and included 3 x 100m-wide breaches in the sea-wall. In the years that followed the seawall breaching, the lower elevation sections of the site gradually accreted with sediment (thus further reducing the tidal exchange volumes with the Roach Estuary over time). A morphological complex and biodiverse wetland was created. On 13th January 2020, a standard Wetland Bird Survey (WeBS) of this site showed that it supported 19,056 birds (including 8,200 Knot, 4,000 Dunlin, 1,964 Grey Plover, 1,000 Golden Plover, 1100 Black-tailed Godwit). During the same survey over 33,000 birds were recorded across Wallasea island as a whole.

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