Jacobs: Steart Marshes Managed Realignment Scheme
A sustainable approach to flood protection involving community engagement, hydrodynamic modelling and environmentally friendly construction practices.
What we know
In the UK, managed realignment is the most common method to restore coastal habitat.
This allows the sea to return to areas that had previously been reclaimed from it by creating carefully planned breaches in coastal flood barriers. It can offer a sustainable, long-term management option that restores valuable habitats while reducing pressure on flood defences [source].
In much of the northern hemisphere, saltmarshes and mudflats have historically been reclaimed from the sea to produce grazing or agricultural land. But over the past 20 years, recognition of the value of these areas has increased – due to their role as habitats for sensitive species and for their provision of natural defence against coastal erosion and inland flooding.
Restoration efforts have therefore become more common [source].
The Steart Coastal Management Project undertook a combined managed realignment, with regulated tidal exchange and freshwater restoration techniques used to create a range of sustainable coastal habitats, compensating for habitat losses elsewhere in the Estuary due to rising sea levels.
Image credit: WWT
What we’re doing
requiring detailed hydrodynamic modelling to ensure the scheme would create the maximum possible habitat while minimising impacts on the surrounding estuary.
Technical expertise from Jacobs in the design, permitting, construction and monitoring of Steart Marshes resulted in the successful creation of new valuable habitat.
Since being breached, the new exit channel from the marshes has been carefully monitored in cooperation with academic researchers to further understand of the hydrodynamic processes at work, to inform similar future projects [source].
Image credit: WWT
What it’s worth
The Steart Coastal Management Project has been one of the UK’s largest coastal habitat creation schemes, restoring over 400 ha of natural habitat including large areas of saltmarsh and mudflat which are home to many sensitive species.
Local villages and roads will benefit from improved flood protection [source] and the habitat creation supports both climate change mitigation (through carbon sequestration) and adaptation (through protection from coastal flooding).
Rigorous modelling enabled the scheme’s planning and option selection to be well-informed about how different decisions would affect the flooding characteristics of the newly reclaimed habitat, and its influence on flood protection of nearby dry lands. Careful planning and collaboration ensured the scheme was cost effective and received planning approval on its first submission.
A separate MSc research project demonstrated the considerable economic benefits from the range of ecosystem services provided by the coastal wetland habitats, valuing them between £500,000 and £900,000 annually in 2008 [source].
The overall result was a reduced risk of flooding to the surrounding community and infrastructure. In addition, 183 hectares of saltmarsh, 40 hectares of intertidal mudflat, 79 hectares of coastal grazing marsh and 26 hectares of freshwater lagoon were created, significantly improving the costal environment and biodiversity.