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  4. Turning the tide Severn Estuary

Connecting the largest river in Great Britain with the Bristol Channel, the Severn Estuary is far more than a stretch of water—it’s an untapped powerhouse with the potential to transform lives, economies and the planet. WSP has been involved in understanding the potential of tidal power from the Severn over many decades working for UK Government, Welsh Government, local authorities and most recently the Severn Estuary Commission. Combining our GoldSET digital platform and deep environmental expertise, with our tidal engineering knowledge, we’re helping the Severn Estuary Commission empower local communities and stakeholders to reimagine what’s possible for the future. By fusing smart data-driven analysis with genuine collaboration, we’re contributing to a bold new course based on tidal energy resilience and prosperity. 

At 14.86 meters between its lowest and highest astronomical tides, the Estuary sports the highest tidal range in the UK and the third highest in the world thanks to its one-of-a-kind geography and coastline. This makes it an ideal source of clean, predictable energy independent of weather conditions. The Severn Estuary has the potential to deliver up to 7% of the UK’s electricity demand. Despite the country’s ambitious sustainability goals, climate change adaptation plans and growing energy demand, making use of that potential has proven difficult.

The factors that make the Severn Estuary such a promising clean energy source—its unique environmental features and the surrounding port communities—also create its greatest sensitivities.

Over the last four decades, there have been numerous tidal range studies and projects that have not progressed in the Severn Estuary and many reached the same conclusion: the large, dam-like barrages traditionally associated with tidal range power schemes would have a significant negative impact on both the ports in the Estuary and its many internationally protected habitats. Those plans also met resistance from local stakeholders and proved too expensive. 

Working with the independent Severn Estuary Commission, our expert teams were confident there could be another option, and that a data-driven analysis could be key to unlocking new insights and possibilities for this location. Alongside our coastal and power engineering capabilities, we brought our environmental specialism, digital expertise and the GoldSET platform to the table, exploring the viability of a smaller, first-of-its-kind approach to tidal energy. This helped guide a comprehensive report that lays out an actionable plan to realize the Severn Estuary’s massive power generation and energy resilience capabilities. 

Location

  • United Kingdom

Project Status

  • Complete
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We knew this project would be different when we received the tender–a unique opportunity to use the latest tech and digital capabilities to support our client and showcase the Severn Estuary's capacity to support tidal energy.
Connor May Senior Marine Consultant, WSP UK
Taking a data-driven approach to planning in complex environments by applying the multi-criteria process that underpins GoldSET consistently demonstrates the balance between transparency and robustness of the framework.
Massimo Dragan GoldSET Technical Director, WSP

Diving into data to find the balance

GoldSET is an innovative, web-based set of Geographic Information System and Multi-criteria Analysis tools that offer a clear, systematic approach for clients to monitor projects and compare options. Essentially, it’s a digital platform to help stakeholder groups visualize large amounts of data across a map view, empowering them to explore solutions and make better decisions. 

Most importantly for this project, the platform is designed and deployed by environmental and digital experts to digest, analyze and present results for massive amounts of geospatial, social and ecological data, which the Estuary and its ecology have no shortage of. Our team embarked on a deep dive of this data with GoldSET, building off previous studies of the Estuary’s environment and the other attempts at tidal energy projects.

Andrew Garrad, Chair of the Severn Estuary Commission, explains that “We are faced with a conundrum–we know that we need a lot more electricity to meet our decarbonisation targets, and we know that it should be local and low-carbon. Equally we know that all projects have an environmental impact. Balancing a project’s environmental impact with its broader environmental and economic benefit is the key compromise to be made when considering renewable energy.”

The commission was launched by the Western Gateway Pan Regional Partnership to assess the feasibility of developing tidal range energy from the Severn Estuary given the volatile energy cost increases following Covid and the Ukraine war. The context is the contribution the region could make, as part of the larger effort to drive the UK towards its 2050 net zero and energy cost reduction goals, while also creating regional economic growth and sustainable energy development from the Estuary. 

Using our engineering and environmental expertise, alongside inputs from financial and socio-economic consultants, the Severn Estuary Commission was finally able to buck the trend of previous studies.

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Pushing past limits to uncover new opportunities

In addition to the analysis of different options based on example projects, the team also used the digital tools to workshop, present and discuss key environmental features. This empowered them to conduct an evidence-based review of tidal energy sites across the Estuary in consultation with regulators and major stakeholders. GoldSET guided us to a similar conclusion as prior studies: the barrages used in most tidal energy generation projects are too damaging to the Severn Estuary’s unique environment.

This conclusion was reinforced by stakeholders and the options analysis quickly confirmed that a viable alternative existed in the shape of a tidal lagoon, larger than had been proposed before but located in a less sensitive area of the estuary. This formed the basis of the Commercial Demonstration Project recommended by the Commission.

It comprises a marine wall that forms a relatively small enclosure along the coast, taking up a fraction of the size of a barrage. Where a barrage would stretch across the Estuary from one shore to the other, a lagoon instead resembles a harbour or marina, occupying space on only one side of the shoreline with its smaller footprint. This would allow wildlife and ships to continue passing through the Estuary unhindered, where a barrage would be large enough to obstruct ocean traffic and damage a large swathe of delicate ecosystems. A lagoon would also be less expensive to construct, with the opportunity to build one or more further lagoons in other parts of the Severn Estuary.

The team then used GoldSET to compare how a lagoon and barrage would perform in each potential tidal energy site, using the wealth of data drawn from the estuary’s environment during their analysis. With these metrics, they were able to demonstrate the environmental impacts and energy outputs of each installation – and in turn, why the lagoon was a much better option for the estuary’s unique ecology and the surrounding communities.

The conclusions showed that a lagoon would serve as the most economically and environmentally efficient option, allowing further study of the unknown impacts of tidal development, while also being less disruptive to the Severn Estuary’s unique environment.

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A clearer path ahead for climate change adaptation

In addition to the low-carbon electricity generated and its contribution to the stability of the national transmission grid, a lagoon would also create local jobs during its construction and could offer some amount of protection against sea level rise. Local economic and environmental stakeholders were far more receptive to these plans, in contrast with their almost universal pushback against a barrage. 

“We are pleased to have had this opportunity to support the commission in the evaluation of renewable energy production and that the application of a multi-criteria framework provides a robust foundation for future decisions, that take into consideration the different perspectives and tradeoffs that a project of this scale would require”, noted Massimo Dragan, GoldSET Technical Director.

The report also found that if the initial lagoon is successful, it could lead the way for future installations around the UK, enhancing supply chain opportunities, reducing consumer costs over its long lifetime, improving environmental data collection and helping deliver its net zero goals.

Following the publication of the Commission’s report, WSP has been retained to undertake the environmental and engineering studies to identify acceptable locations for the recommended Commercial Demonstration Project. 

“Although a tidal lagoon is smaller than a large barrage, it is still a significant energy project with an installed capacity of more than 500MW and a projected lifetime of more than 100 years”, notes Peter Kydd, WSP’s tidal power lead. He concludes “Tidal power is a unique example where coastal and hydropower engineering skills co-exist with environmental knowledge and experience to deliver a natural and sustainable energy solution for the next century.” 

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