The Estuary

Severn Estuary Tidal Power - Resource Page

Photo of the Severn Crossing, by Jonny Page

Tidal Power in the Severn Estuary and Inner Bristol Channel


Since the UK Government is committed to generating 20% of the nation's energy from renewable sources by 2020, tidal power in the Severn Estuary could contribute significantly to this target, particularly given the estuary’s high tidal range (second highest in the world). However any schemes are inevitably going to have a range of impacts, from those on habitats and wildlife to those on shipping and ports.

For these reasons tidal power in the Severn Estuary has never been far from the headlines with a range of proposals, including various barrages, tidal lagoons and other schemes, being discussed and debated at both national and local levels.

The Department for Energy and Climate Change announced last year (9th June, 2015) that it had given the Tidal Lagoon Swansea Bay proposal development consent.

Since before the New Year doubts had been expressed over the future of the project after being imposed with a delay of a year, and reports that the government's enthusiasm had cooled in relation to the high strike price.

Most recently, reports have stated that the strike price for the project could be much lower than previously stated, and on a par with the strike price for the new Hinkley Point nuclear power station proposal, also sited in the Severn Estuary area.


Latest News

Other News Articles

Tidal Lagoons


What is a Tidal Lagoon

A harbour- type structure closing off a tidal sea area, and incorporating hydro turbines through which the sea moves to generate electricity.

Further explanation and video (BBC)


Currently, there are various proposals to harness the tidal power in the estuary and parts of the Bristol Channel as well as at other sites in the UK, potentially providing up to 10% of the UK's electricity needs.  Around the estuary/Bristol Channel:

  • Tidal Lagoon Swansea Bay
    • The world’s first, man-made, energy-generating lagoon, with a 320MW installed capacity and 14 hours of reliable generation every day.
    • Renewable and predictable power for over 155,000 homes (equivalent to 90% of Swansea Bay's annual domestic electricity use) for 120 years.
  • Tidal Lagoon Cardiff
    • The UK's first full-scale energy-generating lagoon, with between 1,800MW and 2,800MW installed capacity
    • Renewable and predictable power, enough to power all Welsh homes, for 120 years


Severn Barrage


What is a Tidal Barrage

A dam-like structure spanning a tidal estuary or  inlet. It utilises the potential energy (from the difference in height between high and low tides) to generate electricity



Over the last decade or so, there has been considerable interest in a range of barrage proposals for the Estuary and Inner Bristol Channel.  These have included:

  • The Cardiff – Weston Barrage: from Lavernock Point near Penarth to Brean Down near Weston-super-Mare (2013).
    • This proposal was promoted by Hafren Power, a private sector consortium including major engineering and construction companies (2013).
  • The Government’s Severn Tidal Power Feasibility Study Consultation on a range of barrage and lagoon options (2008 – 2010)
    • this explored a range of technologies, including several barrage alignments.  The study aimed to help identify the best way of capturing the enormous renewable energy resource of the Severn estuary whilst safeguarding its internationally important combination of species and habitats, and bring lasting benefits to local communities. 


Websites, Reports and Conferences

All website links correct as of 10/06/2015, please contact [email protected] if you find any that are broken.

Tidal Power Links in the Severn Estuary and Bristol Channel


Background to Tidal Power on the Severn Estuary

In July 2008 the Government published a list of ten possible schemes, including barrages, onshore and offshore lagoons, a tidal fence and a tidal reef. They then assessed, in high level terms, the costs, benefits and impact of potential schemes and how they might affect the environment and the region. Following this process Ministers recommended the following schemes for detailed analysis:

  • Shoots Barrage - located near the Severn road crossings, estimated to cost £3.2bn to construct and generate 2.7TWh/year or just under 1% of UK electricity
  • Beachley Barrage - slightly smaller and further upstream than the Shoots Barrage (and upstream of the Wye), estimated to cost £2.3bn and generate 1.6TWh/year
  • Fleming Lagoon - an impoundment on the Welsh shore of the Estuary between Newport and the Severn road crossings, estimated to cost £4bn and generate 2.3TWh/year
  • Bridgwater Bay Lagoon - an impoundment on the English shore of the Estuary between Hinkley Point and Weston Super Mare, estimated to cost £3.8bn and generate 2.6TWh/year
  • Cardiff-Weston Barrage - located between Brean Down and Lavernock Point, estimated to cost £20.9bn and generate 16.8TWh/year or some 4.4% of UK electricity.


New Scientist Map of short list
Original long list of options

Original list of 10 Tidal Power options (BERR)


The five projects selected were those that the government's engineering consultants, Parsons Brinckerhoff, deemed to be based on the most proven technology. Proposals for tidal reefs and tidal fences were not included. The former would involve a series of slow-moving, fish-friendly turbines over a purpose-built causeway in the estuary while the latter would involve building only a partial barrier between Cardiff and Weston-Super-Mare. Both these proposals are acknowledged as having minimal impact on the local environment.

There were allegations that Parsons Brinckerhoff miscalculated the costs of a tidal lagoon project championed by Friends of the Earth. The report sent by the consultants to ministers stating the tidal lagoon option would be eight times more expensive than the barrage scheme and would not generate as much power, claims denied by the designers. David Elliott, of the energy and environment research unit at the Open University, also stated that a single big barrage would be problematic in terms of harnessing energy since it would only provide two short bursts of power every day. He considered that several smaller tidal turbines around the coast, operating at different times, would be a better solution. Likewise the RSPB was disappointed that the Cardiff-Weston barrage option was on the short list, considering that the final scheme must be the one that generates as much clean energy as possible, while minimising harm to the estuary and its wildlife. They considered that the barrage would destroy huge areas of estuary marsh and mudflats used by 69,000 birds each winter and block the migration routes of countless fish.

The Partial Impact Assessment of Severn Tidal Power prepared for the Department of Energy and Climate Change compares the five projects against the “do nothing” option, which was considered to be the generation of electricity from Combined Cycle Gas Turbines and other options for meeting renewable energy and GHG targets. It also stated that there may be a regional economic cost to ports and to local fishing, additional environmental costs from the loss/damage of habitats and species, reduced ‘ecosystem services’ including negative effects on biodiversity and harm to fish stocks.

Because of these issues and others, the Sustainable Development Commission, the UK Government’s independent watchdog on sustainable development, set out three ‘sustainability tests’ which a Severn tidal power scheme should pass:

  • It must be publicly led as a project and publicly owned as an asset, in order to avoid short-termist decisions and ensure the long-term public interest
  • It must go ahead in full compliance with EU Habitats and Birds Directives, which will require assessment of mitigation and compensation on a scale as yet unseen in Europe
  • Any tidal power scheme must not divert Government attention away from much wider action on climate change

The Severn Tidal Power Consultation phase closed on the 23rd of April 2009. For information on the second phase of the study, please visit the Department of Energy and Climate Change's Severn Tidal Power Feasibility page, or the Welsh Assembly Government's Severn Tidal Power page.

Note: It is not the intention of the Severn Estuary Partnership to take any position regarding the debate about tidal power in the estuary, merely to provide a resource on the subject. About us. The different groups on the estuary and their various websites are easily viewed from the Severn Estuary Gateway.


About the Severn Estuary Partnership

At the Severn Estuary Partnership, we aim to keep all of our stakeholders informed of renewable energy developments and proposals that are happening within, or will have an impact on, the Severn Estuary, acting as a neutral facilitator, encouraging discussion and debate.

Your comments - we welcome comments on the proposal and aim to provide a summary of these within our monthly E-news. Get in touch now!

Your actions - if you are holding any meetings or workshops related to the Cardiff Tidal Lagoon proposal, please get in touch to include in our next E-news edition.

About us. The different groups on the estuary and their various websites are easily viewed from the Severn Estuary Gateway.


State of the Severn Estuary Report

This document is set to be the first in a series that reports on the state of and changes in the natural and human environment of the Severn Estuary, establishing baseline data in the context of climate and other coastal change.

One of the main objectives was to inform a wide ranging audience, including local people and industry professionals alike, on why the Estuary is so unique by providing a non-technical overview of the Estuary environment; focusing on its uses and resources.

Future editions of the report will focus on the identification and analysis of a robust set of sustainability indicators, which can not only be used to determine the health of the Estuary environment and its resources, but will also aid in the development of effective management measures.

State of the Severn Estuary Report

The ‘State of the Severn Estuary Report’ has been produced by the Severn Estuary Partnership and Cardiff University, in collaboration with the Environment Agency (Wales). With support from the Interreg IVb IMCORE project, the report has been developed to incorporate contributions from the University’s lecturers, local industries, stakeholders and even Estuary residents – such as Miranda Krestovnikoff, presenter of the BBC’s Coast series – who kindly wrote the foreword and launched the summary document at the 2011 annual Severn Estuary Forum.

Back to top of page

Bookmark and Share
© 2002-2012, site maintained by Severn Estuary Partnership | ContactCopyright flickr twitter facebook