The Severn Barrage
History
The idea of a Severn Barrage is nothing new. Early proposals in the mid 1800's were mainly driven by harbour creation, flood defence and transport links across the estuary. From the 1920's onwards, however, initiatives were more born out of aspirations to harness the energy from the Severn's 14 metre (45 foot) tidal range, the second largest in the world.
The Severn estuary is a habitat that is unique for its massive intertidal zones and huge volumetric flows of water. It is a vast overwintering site for a whole range of migrating birds but of particular relevance for the Foundation, it is the conduit for several extremely rare migratory fish species: Allis and Twaite shad; Sea and River lamprey; Atlantic salmon and Sea trout and European eel.
Against the background of climate change, the need to drastically reduce the use of fossil fuels that release stored carbon and a timely opportunity to renew or upgrade our outdated and under invested power generation systems, the government is investigating all potential "renewable" sources of electricity generation. For full details please see http://www.berr.gov.uk/whatwedo/energy/whitepaper/page39534.html
An inspection of the Severn estuary and its huge tidal range would suggest that there should be potential for harnessing the massive forces of water movement to generate renewable electricity, thus reducing our dependency on fossil fuels.
Drivers for the Barrage
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30% of UK's electricity generation will be lost by 2020.
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40% of our electricity needs to be from renewables (currently < 1% but targeted at 10% by 2020).
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Populist and big business pressure.
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Tidal power is a genuine renewable source.
In October 2007, the Sustainable Development Commission looked into the UK's tidal energy possibilities, including the Severn estuary. Some of their conclusions were:
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A Severn Barrage should be part of a wider action on climate change.
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It must comply with existing environmental legislation i.e. Habitats Directive.
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Provision of compensatory habitat is an integral part of any proposal.
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Early work on scientific and legal feasibility of compliance and cost should be a priority.
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The Severn tidal range could generate 5% of UK electricity.
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The Severn tidal stream resource is not one of UK top ten sites.
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The project should be government owned and run.
See www.sd-commission.org.uk/publications.php?id=607 for the full report.
2009 Where are we now?
A government feasibility study, started in 2007, concluded its first phase when a public consultation was launched on 26th January 2009. This public consultation was finished on 23rd April and covered, amongst other things, the proposed scope of the Strategic Environmental Assessment (SEA) for up to 11 possible barrage schemes. This was shortlisted to 5.
A consortium led by the engineering consultants, Parsons Brinckerhoff (PB), has been appointed to manage this part of the project. The study will culminate in a full public consultation in 2010.
| Proposal | Location | Installed Capacity | Construction Cost | CO2 Savings/year |
| Shoots Barrage | By Severn road crossings | 1.05 GW | £3.2bn | 1.2 Mt |
| Beachley Barrage | Just upstream of the Wye confluence | 0.625 GW | £2.3bn | 0.7 Mt |
| Fleming Lagoon | Between Newport & Severn Road crossings | 1.36 GW | £4.0bn | 1.0 Mt |
| Bridgwater Bay Lagoon | English shore between Hinkly Pt & Weston Super-Mare | 1.36 GW | £3.8bn | 1.1 Mt |
| Cardiff-Weston Barrage | (Lavernock Pt - Brean Down, known as Severn Barrage) | 8.64 GW | £20.9bn | 7.2 Mt |
So what are the Issues for us?
One would expect an environmental organisation set up to restore and protect fish and fisheries to be against any scheme that could severely reduce or extinguish runs of migratory fish. Salmon, shad and lamprey currently enjoy the protection of the EU Habitats Directive. The schemes shortlisted will present massive problems for planners attempting to reconcile these important environmental considerations. We believe that this crucial aspect should have been reflected in the short listing as the issue of providing compensatory habitat is such a "Significant Challenge" that the process may be set back very substantially while resolution is investigated. Equally, the barrage presents huge challenges to one of the most important RAMSAR sites, where birds both live and over-winter in the unique habitat. Colleagues in the RSPB, WWF, Wildfowl and Wetlands Trust (Slimbridge) and other wildlife trusts therefore have parallel concerns and together we are creating a united front. The size and strength, experience and ability of these organisations make for welcome allies.
There are, however, plenty of other reasons for opposing the barrage, amongst which are ...
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It's disproportionately expensive (see table below).
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Tidal Power is Intermittent: power produced at night and in short, heavy bursts requiring grid restructuring
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It won't solve the problem of either Climate Change or Power Generation as effectively as some other schemes.
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There are as yet unresolved technical issues.
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There is a lot of money involved.
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It's a risky "all eggs in one basket" scheme.
Are there better alternatives to the Barrage?
The table above would suggest so. The list of potential alternative sources of energy includes ...
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Tidal stream – elsewhere in UK.
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Wind power (sea and land).
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Nuclear.
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Micro generation – new technologies being developed.
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Energy conservation (turn off the lights!).
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Tidal reef.
Tidal Reef
One of the 11 original schemes was a proposal by Evans Engineering for a 12-mile tidal reef stretching from Minehead to Aberthaw. The reef gives the prospect at least of being environmentally benign, ie allowing fish to pass and only slightly reducing the intertidal zone, so important for birds. It would permit shipping to pass and generate at least as much electricity as any other scheme, probably over a longer period. Despite strong support for this scheme from environmental organisations, it did not make it onto the shortlist of 5 with the Government saying that tidal reef technology was not yet developed enough. They added, however, that this and other schemes could be revisited before any final decision was taken and promised some funding for further research.
Advantages of the Tidal Reef:
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Works on low head ... 6'.
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Less demanding structure .
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Many slow turning turbines.
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Situated a long way down the estuary.
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Generates for a longer period - on both tides.
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Less change to intertidal zone.
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Shipping OK.
What has the Wye & Usk Foundation done about the Barrage proposals?
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We sit on the Strategic Environment Assessment Steering Group.
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And Migratory Fish Technical Group.
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We have joined with other NGOs such as the RSPB, WWF, WWT and WTs to form a robust resistance to environmentally unfavourable schemes.
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Submitted papers at call for evidence.
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Two presentations to at WSFOA and UUFA AGMs.
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Presentations to Parliamentary groups.
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Responded on your behalf to the Public Consultation (see pdf below).
What next?
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Continue with lobbying, attending steering group and technical meetings.
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Working with other NGOs to resist any unfriendly scheme and ensure the existing SAC legislation is upheld.
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Press for the best environmental solutions to Climate Change.
2010 - The government has announced that it will not fund a Severn Tidal Scheme
The key conclusions of the feasibility study were:
- A tidal power scheme in the Severn estuary could cost as much as £34billion, and is high cost and high risk in comparison to other ways of generating low-carbon electricity.
- A scheme is unlikely to attract the necessary private investment in current circumstances, and would require the public sector to own much of the cost and risk.
- Over their 120 year lifetime, Severn tidal power schemes could in some circumstances play a cost-effective role in meeting our long term energy targets. But in most cases other renewables (e.g. wind) and nuclear power represent better value. Moreover, as a Severn scheme could not be constructed in time to contribute to the UK’s 2020 renewable energy target, the case to build a scheme in the immediate term is weak.
- The scale and impact of a scheme would be unprecedented in an environmentally designated area, and there is significant uncertainty on how the regulatory framework would apply to it. The study has considered ways in which to reduce impacts on the natural environment and also how to provide compensation for remaining impacts on designated features. It is clear that the compensation requirement would be very challenging, however defined, and require land change within the Severn estuary and probably outside it also.
- A scheme would produce clearer, calmer waters but the extreme tidal nature of the Severn estuary would be fundamentally altered. This means that some habitats, including saltmarsh and mudflat, would be reduced in area, potentially reducing bird populations of up to 30 species.
- Fish are likely to be severely affected with local extinctions and population collapses predicted for designated fish, including Atlantic salmon and twaite shad. This could mean the loss of twaite shad as a breeding species in the UK as 3 of the 4 rivers where it breeds run out into the Severn estuary.
- Water levels would also be affected and in order to maintain current flood protection levels in the Severn estuary additional flood defences would be required; these costs are included in the cost estimates for each scheme. In turn, such defences would provide longer-lasting protection to the affected areas.
- Overall a scheme is likely to benefit the regional economy with net value added to the economy and jobs created. However, these benefits would come at the expense of negative impacts on the current ports, fishing and aggregate extraction industries in the estuary.
- The Cardiff-Weston barrage is the largest scheme considered by the study to be potentially feasible and has the lowest cost of energy of any of the schemes studied. As such it offers the best value for money, despite its high capital cost which the study estimated to be £34.3billion including correction for optimism bias. However, this option would also have the greatest impact on habitats and bird populations and the estuary ports.
- A lagoon across Bridgwater Bay (£17.7bn estimated capital cost) is also considered potentially feasible, as is the smaller Shoots barrage (£7bn). The Bridgwater Bay lagoon could produce a substantial energy yield and has lower environmental impacts than barrage options. It also offers the larger net gains in terms of employment.
- The Beachley Barrage and Welsh Grounds Lagoon are no longer considered to be feasible. The estimated costs of these options have risen substantially on investigation over the course of the study.
- Combinations of smaller schemes do not offer cost or energy yield advantages over a single larger scheme between Cardiff and Weston. (See map of scheme options in Figure 5 and an explanation of tidal range technology in Chapter 1).
- In addition, the study funded further work on 3 proposals using innovative and immature technologies. Of these, a tidal bar and a spectral marine energy converter showed promise for future deployment within the Severn estuary - with potentially lower costs and environmental impacts than either lagoons or barrages. However these proposals are a long way from technical maturity and have much higher risks than the more conventional schemes the study has considered. Much more work would be required to develop them to the point where they could be properly assessed. Correspondingly, confidence levels on their yields, costs and impacts (including environmental impacts) are much lower at this point.
- Many years of further detailed work would be needed to plan, finance, and assess the impacts of such a large structure as a Severn power scheme before a case could be put forward for planning consent. Even over a period of 2 years this study has only been able to consider feasibility and impact at a strategic level. If consented, the construction times would be between 4 and 9 years depending on the scheme. In addition, any of the schemes would first require new habitats to be created, or species re-introduced, to replace those that would be displaced. These habitats and measures require time to be effective.
Please click here to read the full report. None of the forgoing precludes a private company from creating a tidal barrage scheme.
Further reading:
