Gwyn Williams, Head of Reserves and Protected Areas, contributes this blog about the Severn Barrage, following this week’s publicity around a new proposal by Hafren Power:

With a week gone, Martin’s prediction that it was likely to be a quiet fortnight is looking a little insecure, given the coverage over the weekend [19 August] to a new proposal from Hafren Power for an energy-generating barrage across the Severn!

In thinking about energy, the RSPB starts from a similar place to most, including those who support a Severn Barrage: we need a renewable energy revolution to combat climate change. However, if energy developments are not to put even more pressure on a natural environment that is already deeply stressed and further threatened by climate change, we need to make sure we use the right renewables in the right places.

The potential for energy generation from the Severn has attracted engineers since Victorian times. The most recent DECC study focussed on whether a scheme generating maximum power using current technology could be economic, and if so with what side-effects, including - very much as a secondary consideration - impacts on the natural environment. The RSPB strongly criticised this approach: we thought that the starting point should be to look for a type of technology which could provide maximum energy output from the Severn for minimum environmental harm. It took two years and a small forest of paper to conclude that construction of a high-head barrage with high-velocity turbines would be too costly, and result in big negative environmental side effects.

Now Hafren Power has resurrected the idea, with a lower-head, low-velocity turbine concept, that it believes can still produce c5% of UK electricity needs, but with less harm to the environment than the high-head, high-velocity options which have been the focus of barrage proposals to date. The company has now presented its ideas to the Prime Minister, David Cameron, in a meeting brokered by ex-Welsh Secretary, Peter Hain MP. Mr Cameron is reported as being very interested and has instructed officials to look into the project.  Powerful sponsorship indeed!

The undertaking remains mammoth – a wall over 18km long, housing over 1,000 turbines of 9 metres in diameter across an estuary with the second highest tidal range in the world.

The company claims the barrage can be built without up front public funding, and that it can raise £30bn needed without public money, using sovereign funds from Qatar and Kuwait. Its ask of the UK Government is that the electricity generated should be subsidised in the same way as offshore wind energy, and that time should be made available for the ‘hybrid’ Parliamentary Bill necessary to give powers to the company to construct it.

The big worry is obvious – that in order to give investors confidence to back the scheme, Government will reduce the scrutiny process to a minimum (think red-tape challenge, and all the proposals for planning reform!). We can expect the checks and balances on development projects created by the Birds and Habitats Directives to come under renewed pressure. It is also obvious that consumers will be expected to pay for the scheme through the new subsidy system that Government is currently designing as part of the Energy Bill, and that will be key to the scheme‘s viability. This will also have considerable implications for other forms of renewable power generation, given the current Treasury cap on renewable generation subsidies.

So what are the environmental concerns? The big one is that whilst a lower-head barrage should reduce the immediate loss of mudflats, which are the reason why the Severn is so important for wildlife, the geomorphological impact of the structure will be felt for many decades and quite possibly over several centuries – and could eventually result in an impact as severe as the high head option. Removal of so much energy from the Severn is likely to result in sustained erosion of mudflats and saltmarshes, as the estuary seeks to find a new equilibrium to match the conditions created by the presence and operation of a barrage. 

Once lifted by the tides, sediment is likely to be deposited into the deepest parts of the estuary in an attempt to reduce the depth of the channel. The result could be the loss of protective mudflats and the undermining sea-defences within the estuary - bad for wildlife and bad for people. The Dutch understand this well, having seen changes of this kind following the Eastern Scheldt barrage.

The risk of extinction of important fish populations has always been a major concern in relation to tidal power generation in the Severn. The threat to migratory fish from low-velocity turbines should be less, but to date we have not seen evidence to support this, and much will depend on the design and deployment of untested technology.

We continue to regard estuarine barrages with scepticism because of their high cost and potential for environmental damage.  However, as with the DECC study, we will seek to work constructively with Hafren Power to contribute to understanding of the implications of their proposals. A structure that will be with us for more than a century is just too big to get wrong!

  • Gwyn,  I dont fully understand what high head and low head actually means and I am a bit biased having grown up on the edge of the tidal Severn Estuary. Logically any 18km barrier is bound to cause serious effects on tides, silting, mudflats and bird life, let alone the fish stocks, eels etc.    One of the stated mitigation proposals for the original barrier proposal was to improve bird feeding areas in the Thames estuary.  How does that now feature with pressure on for an airport in exactly that location.

  • Excellent blog Gwyn. I think the RSPB is 100% right to regard estuarine barrages with an awful lot of scepticism. One always has that lingering feeling that the tax payer (you and me) will end up footing the bill and the environment and the wildlife will be damaged beyond repair in ways that, with such a large and complex estuary system, it is almost impossible to predict. Meanwhile the clever developers walk away with plenty of financial gain.

    I do think the very bad experience of the Dutch regarding their Eastern Scheldt Barrage is a very important factor to bring into play in this debate very early on.

    A barrage is definitely "a bridge" much "too far". There are technically many other ways of harnessing the natural power of the Severn in far less riskier, costly and less evironmentally damaging ways.

    The RSPB will have my full support in their efforts to achieve a solution that results in green power WITHOUT significant envronmental damage to the Severn Estuary and a barrage is unlikely to feature in that equation

  • Could you explain to me also how removal of energy from the Severn leads to greater erosion? the Severn is an extremely powerful and turbid estuary with very strong currents and a high proportion of sand banks; its wildlife interest is scattered and thinly distributed on a very large estuary bar Bridgwater Bay. I would have thought that reducing this tidal power by placing a barrage across it would have lead to greater deposition of mud and an increase therefore in the wildlife interest ? This is counter intuitive and you say this reverse is true; can you clarify.

    Also I hope that RSPB will help me make this a key issue at the Bristol Mayoral election. Which option does Bristol prefer barrage or tidal, as the city and Green Capital of Europe which will be most profoundly affected, while its port will have its competitive advantage reduced to the advantage of Port Talbot. It can not be a coincidence that this Welsh port is most adjacent to Peter Hain's constituency.

    There is a consensus on the Bristol side of the estuary that this is not the best option and this audience should be played to; and hard.

  • Hi,

       There are other options are there not ? Why do RSPB comments in press today not give this option ? Lagoons and reef technologies could generate as much energy I am informed by Tidal Electric without affecting so profoundly the core dynamics of the estuary; if very substantial structures. I do not understand why RSPB seems to endorse this position when there are less damaging options ? Veils and mirrors ?

         I am even more concerned by the prospect of a Middle Eastern conglomerate having a large stake in a globally significant renewable resource that is key to our strategic independence in the future. Selling off our non carbon future; Hain has nt yet visited Bristol the Labour Party in the City most likely to be affected; ? Does he have Labour Conference endorsement ? Why can pension funds etc not be persuaded to back lagoons and reefs for a lower cost electricity and competitive energy future ?