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The proposed Severn Barrage

PUBLISHED: 11:40 19 January 2010 | UPDATED: 14:58 20 February 2013

Barrage of constraints

Barrage of constraints

An environmentalist's dream or environmental nightmare? Mark Child and Katie Jarvis examine the pros and cons of the proposed Severn Barrage.

The tidal range in the River Severn's estuary is between fourteen and fifteen metres, making this the second-highest in the world. The highest is in Canada's 174-mile-long Bay of Fundy, where the tidal range is sixteen metres. The Severn's tides have the energy to drive sufficient turbines to generate a variably estimated five to eight per cent of the UK's electricity requirement, in a way that is less polluting than by other means. Estimates also suggest that the resulting output of power might be equal to that of up to three nuclear power stations. This would be the largest single renewable energy resource in the UK, and would help to reduce the emissions of so-called greenhouse gases, such as carbon dioxide.


Reports suggest that one way of achieving this would be to build a barrier across the estuary between the coast of Wales, and that of England. Indeed, the idea of a barrage across the Severn, for a number of reasons, has been seriously mooted since the 19th century and plans for it were drawn up in 1849. At the currently proposed point, the water is about 200 feet deep, and travels at some four knots. At today's prices, the estimated cost of the building work would be around 15 billion, but speculative projected timescales vary considerably between six and twenty years. It would be a civil engineering project on a massive scale.


Civil engineering projects are the bread and butter of one of the most interested parties of recent years, the Severn Tidal Power Group. This consortium of six power engineering and construction companies was set up in 1984 to investigate how a barrage project might be carried forward. In 1933, the Government's Severn Barrage Committee had endorsed the idea, and another Severn Barrage Committee's response to energy prices in the late 1970s, particularly with regard to oil, seriously awoke the spirit of building across the River Severn. The Severn Tidal Power Group produced a study in 1986, but its subsequent investigations have been subjected to political and industrial considerations.


Tidal Electric, an organisation whose approach is to create electric power by harnessing the power of tides, has also been involved in recent years. Since 2006, Neath businessman Gareth Woodham has also been part of the programme of study surrounding the Severn barrage concept; he furnished detailed plans for a Severn barrage that also had social and residential implications, and extensive landscaping, as well as facilitating shipping.


In October 2007, the Sustainable Development Commission published a report on the potential for tidal power in the UK. It referred especially to a proposed 200-turbine Severn barrage between Lavernock Point near Cardiff and Brean Down near Weston-Super-Mare. It also made other assumptions: notably that the barrage would operate on the ebb tide, with additional 'flood pumping' to increase the total energy output. Operating only on the ebb tide has proved to be a point of discussion. It would generate electricity for between seven and eight hours on each tide, at the same time producing a variable output. The result would be 17TWh per year, or the equivalent of 4.4% of the UK electricity supply. This is less than earlier estimates for a Severn barrier, being only the equivalent of two 1GW power stations. In terms of coal, it would replace 18 million tons.


There are other perceived benefits of such a barrier, although the SDC concedes that these are 'only marginal to the economic case for its construction'. For example, it would give additional flood protection to low-lying land beside the estuary; there could be an upstream benefit against the risk of coastal flooding; and it would counter the effect of rising sea levels. It might possibly facilitate additional road and rail links. These are considered to be subordinate to the primary objectives of any Severn barrage, but may well assume greater importance in the minds of private financiers of the project. They would, of course, proceed with an eye to maximising the potential for financial return; such communication links could be an income source.


There is also the prospect of stimulated economies to be considered. These may have nothing whatsoever to do with economically produced and sold electricity by means of tidal power per se, but the means of obtaining it through a Severn barrier building programme would need a significant workforce for a considerable period of time. This might be a considerable job creation scheme in itself. It is certainly a programme that would impact very favourably on local Severn-side economies for several years in the comparative short-term, whilst the completion of such a scheme could revitalise the economies of south-west England and South Wales. These are political considerations, but who can yet say whether the barrage's concomitant beneficial financial implications to the Treasury may be the deciding factor?


The concept of damming the Severn, or crossing it with such a barrier, is not new. Nor is there anything unusual in the idea of harnessing its power to generate electricity. Individuals, groups, committees and private building companies have all variously come up with reports and recommendations on how to go about this, the perceived optimum routes across estuary or river, the composition of its working parts, and the amount of electricity each project might be expected to generate. Indeed, there is a very complex debate, running concurrently with the latest report on a Severn barrier, on whether the work should be Government- or privately-funded. This devolves on the relative drawbacks, the benefits to the eventual funding sources and tax-payers per se, and the effects on electricity consumers.


Over the course of time, about ten crossing locations have been suggested, previously up to ten miles in length. These range from the longest point, effectively across the Bristol Channel; through the Severn Estuary, to about a mile upstream on the river. A former favourite was the point at which the Severn road bridge now connects Beachley with Aust; another was where the second Severn crossing now joins Caldicot with Severn Beach. In the latest proposal, for a site between Lavernock and Bream, there would be a tidal lagoon behind the barrier, roads and a railway running across the top, a dozen man-made islands, and four marinas.


The relatively new factor in all of this is the public awareness of the current global climate change and its possible impact on the UK. In the past, virtually all investigations into a Severn barrage have been carried out in a spirit of desirability rather than perceived immediate need. These have included reasons of flood protection, in order to build a huge harbour, and as a transport link. Such studies have been undertaken fairly regularly since the 1920s. They have mostly faltered when successive governments realised the extent of the engineering feat required, and, more importantly, the cost involved. Costs have progressed steadily from some 5 million around eighty years ago, to the estimated billions of more recent years.


Also, until fairly recently, the Severn barrage has not been a political issue. It did not have the potential to enhance any British government's rating with its voters. Messages about climate change, energy conservation in the home, and recycling initiatives - and the high-level stances being taken on each by the political parties - is changing voters' attitudes. As if climate change were not enough in itself, there is also the matter of dwindling global natural fuel resources, in particular crude oil. These are issues that don't seem to be of great concern to most people, and others are at best ambivalent. Yet these issues and the Severn barrage are effectively separate parts of the same energy debate.


The UK has its own problems. North Sea gas and oil is allegedly on the way out; our fossil-fuel power plants are ageing; and an increasing number of nuclear power plants are coming to the end of their lives. It is predicted that the UK could be facing a huge shortfall of base materials, and generating only half the required energy capacity by the mid-2020s. The Government says that unless we can build a sufficient quantity of privately funded, new nuclear power stations, we shall be in the grip of an unprecedented power shortage. Needless to say, the plans to build a Severn barrage are unlikely to be met with much enthusiasm by the nuclear or oil industries, but would be greeted with approval by the construction industry. Either way, each has compelling vested interests.


The Sustainable Development Commission's 2007 Report makes it quite clear that 'development of a Severn barrage must not divert Government's attention away from much wider action on climate change, including the development of a more decentralised energy system and the reduction of energy demand'. The Commission also realised that in the present climate of ambiguity, a Severn barrier might diminish perceptions of the importance of other major issues, or divert public attention from them. 'The SDC is concerned that development of a highly centralised Severn barrage project could frustrate efforts to reduce energy demand, as consumers perceive a barrage to be a solution to climate change mitigation, relieving them of the need to act'.


The report also says that 'it is possible for Government to deliver on a Severn barrage as part of a comprehensive and radical programme on climate change'. Therein lies the key to the need for action. It is all a very long way from a Government Energy White Paper of 2003 that seemed so dismissive, even as the clouds of the energy crisis gathered. It said '... plans for a Severn barrage would raise strong environmental concerns and we doubt it would be fruitful to pursue it at this stage'. They do; but inaction is no longer an option.


The Government wants the UK's future energy to come from a mix of traditional and renewable sources. It is committed to the idea of generating, by 2020, some 20 per cent of the UK's energy, through means such as wind and tide. The tide alternative is preferred to on-shore wind turbines. Indeed, this is the point at which a proposed Severn barrage meets the nuclear power debate. By 2020, the Government aims to have reduced electricity consumption by 26 per cent on 1990 levels. Also, it has long intended to reduce carbon dioxide emissions by 60 per cent by 2050, even though an increasing number of industry commentators now think this is an unrealistic target. However low they may be in carbon emissions, even the new nuclear power stations will produce radioactive waste. The Severn barrage would not do that.


Electricity generated by the Severn barrage scheme would help to ameliorate the effects of climate change, which is impacting negatively on wildlife in general. However, the Severn project has the potential to impact negatively on the wildlife and landscape of the estuary in particular, and this is causing some concern. The Wildfowl and Wetlands Trust at Slimbridge is understandably anxious, and has counselled the Government to make a fair and balanced assessment of all the alternatives before making any decision.


Also to be considered are the negative effects on the environment of the actual construction, and in the manufacture and transport of the component parts that would eventually make up the barrage. The effects of the barrage would be long-term, because the aim is to build a means of generating electricity for at least 120 years.


In that time, people will recover from its visual presence and from the upheaval of its building. Ecologists argue that this would not be the case for an ecosystem that would be severely damaged, if not destroyed, by building and operating the Severn barrage. This presents an intellectual difficulty for environmental organisations. On the one hand, they approve of moves towards electricity generation from natural, sustainable resources and in ways that leave minimal carbon footprints. Conversely, they cannot condone the destruction of ecosystems that might never recover, in order to achieve it.


The Severn estuary comprises about seven per cent of the UK's estuary total. It is one in which a unique ecosystem has evolved that can cope with the harsh tidal conditions imposed by its funnel shape, the continual shifting around of mud and sand, and water that constantly changes between being salty and fresh. The creatures that inhabit the mudflats and wetlands - all manner of invertebrates, cockles, lugworms, flatworms, ragworms and the like - make them essential feeding grounds for migratory birds, and also for those that stay for a season. It is a crucial food table. Some of the birds that fetch up here, such as the waders, are seriously under threat because elsewhere their habitats are fast disappearing. Among the bird population of the Severn estuary are dunlin, redshank, oyster-catcher, ringed plover, curlew and shelduck. It is said that there are some 80,000 waterfowl, migratory and wintering birds on the site. Fish - eel, lamprey, salmon, sea trout, shad - also pass through to end up higher upstream of the Severn, or in the Avon, Wye, or Usk.


Through this area, by air and water, pass wildlife that make their way directly into the Wye Special Area of Conservation and that of the Usk - both part of the European Natura 2000 network. Environmental changes near the mouth of the Severn could affect these. Any changes here would have to take into account the EU Birds and Habitats Directive, and, say ecologists, would have to be done in such a way that safeguards habitat restoration or alternative supply of mudflats and wetlands to the maximum possible extent. If the Severn estuary's mudflats effectively become a lake, feeding grounds will disappear, as will the birds that depend on them; even though a quite different ecosystem may evolve in their place.


Small wonder that the area is recognised in the Severn Estuary Special Protection Area. Environmental organisations are hoping that UK, European, and international laws that currently protect a number of the sites around the estuary will prove to be sufficiently robust to tip the scales in favour of alternative schemes for harnessing its tidal energy.


Supporters of the Severn estuary barrage project say that the destruction of the local ecosystem, as we know it, is a relatively small price to pay when faced with the huge cost to biodiversity of climate change in the wider context. Others argue that the adverse impact of the project is considerably greater than the benefits. Environmentalists agree that any project of this nature will disturb ecosystems, and possibly destroy them, but many agree that this may be necessary, to a degree, for the ultimate wider good of wildlife and humans. However, many are simply not convinced that all the technologies and build options have yet been considered.


Alternatives such as underwater generators, and a floating barrage that does not affect the mudflats, have been promulgated as being less damaging approaches to the generation of tidal power in the Severn estuary. Others prefer the idea of man-made tidal lagoons, constructed about one mile offshore. These, which Friends of the Earth have called 'a genuinely green alternative', would fill, drain, and generate power on both the incoming and outgoing tides. They might be combined with, it has suggested, a smaller barrage - the so-called Shoots barrage - just below the second Severn crossing.


Of course, there are those to whom the whole concept of a Severn barrage is quite unthinkable and quite unnecessary. Just build three more nuclear power stations, they say, and leave the wildlife alone.



DIVIDED OPINIONS



Backers



Opponents




Jonathon Porritt, Chair of the Sustainable Development Commission: "The enormous potential for a Severn barrage to help reduce our carbon emissions and improve energy security needs to be balanced against the impact on the estuary's unique habitat, as well as its communities and businesses. This is why we believe that any development must be publicly-led as a project and publicly-owned as an asset, in order to ensure that the Government takes full responsibility for taking a sustainable, long-term approach."


"The Sustainable Development Commission is issuing a challenge to Government to embrace a new way of managing this major project. We are excited about the contribution a Severn Barrage could make to a more sustainable future, but not at any cost.


"It is vitally important that all parts of Government - including the Welsh Assembly Government and the South West Regional Development Agency - are actively involved in the project, to ensure that work is fully integrated into regional economic and development plans."



Dr Mark Avery, RSPB Conservation Director: "Tackling climate change is hugely important but this can be done without destroying irreplaceable national treasures like the Severn estuary.


"We should be harnessing the power of the Severn but there are better ways of doing this than by hauling ten miles of concrete into the estuary.


"The government should be aiming to help, not destroy, wildlife and that applies to proposals for green energy schemes just as much as new supermarkets or housing estates."



Martin Spray, Chief Executive of the Wildfowl and Wetlands Trust: "We fully support a shift toward low-carbon energy sources and acknowledge the potential of the Severn Estuary for energy generation. However, the environmental impact of a barrage on this delicate ecosystem is not yet known. The Severn Estuary is a unique ecosystem encompassing saltmarsh and mudflats supporting internationally important populations of wildfowl as well as other notable species such as salmon and river lamprey.


"Any decision needs to be based on sound scientific research to avoid the continued 'trashing' of the natural environment on which we fundamentally depend for our survival and development."



Neil Crumpton, Friends of the Earth Energy Campaigner and author of the group's Severn Barrage Report: "The Sustainable Development Commission is saying that the Severn Barrage would be a flagship project - leading the UK's investment in renewable energy. Yet to seriously damage an internationally important wildlife site in order to generate less than one percent of the UK's energy consumption is not the way to lead the world in sustainable development.
"We urgently need to promote renewable energy initiatives but they need to be the right ones. A combination of large offshore tidal lagoons, possibly in combination with a Shoots barrage or barrier, could produce more energy with more flexibility at much less cost and environmental damage. That's why we propose that such schemes are considered in any further Severn studies, as an alternative to the Severn barrage."



Chris Witts, Severn historian: "It's man playing with nature on too big a scale, without knowing the implications. I'm worried that we won't be able to turn the clock back if it goes wrong. We would lose the Severn Bore, which is a major attraction and the largest bore in Europe. That, to me, is short-sighted.


"Back in the 1960s, the Bristol Channel would be black at night. Now it's lit up like a Christmas tree - unbelievable light pollution. Are we really going to ruin the river to pay for things like that?"


Jonathon Porritt, Chair of the Sustainable Development Commission: "The enormous potential for a Severn barrage to help reduce our carbon emissions and improve energy security needs to be balanced against the impact on the estuary's unique habitat, as well as its communities and businesses. This is why we believe that any development must be publicly-led as a project and publicly-owned as an asset, in order to ensure that the Government takes full responsibility for taking a sustainable, long-term approach."


"The Sustainable Development Commission is issuing a challenge to Government to embrace a new way of managing this major project. We are excited about the contribution a Severn Barrage could make to a more sustainable future, but not at any cost.


"It is vitally important that all parts of Government - including the Welsh Assembly Government and the South West Regional Development Agency - are actively involved in the project, to ensure that work is fully integrated into regional economic and development plans."



Dr Mark Avery, RSPB Conservation Director: "Tackling climate change is hugely important but this can be done without destroying irreplaceable national treasures like the Severn estuary.


"We should be harnessing the power of the Severn but there are better ways of doing this than by hauling ten miles of concrete into the estuary.


"The government should be aiming to help, not destroy, wildlife and that applies to proposals for green energy schemes just as much as new supermarkets or housing estates."



Martin Spray, Chief Executive of the Wildfowl and Wetlands Trust: "We fully support a shift toward low-carbon energy sources and acknowledge the potential of the Severn Estuary for energy generation. However, the environmental impact of a barrage on this delicate ecosystem is not yet known. The Severn Estuary is a unique ecosystem encompassing saltmarsh and mudflats supporting internationally important populations of wildfowl as well as other notable species such as salmon and river lamprey.


"Any decision needs to be based on sound scientific research to avoid the continued 'trashing' of the natural environment on which we fundamentally depend for our survival and development."



Neil Crumpton, Friends of the Earth Energy Campaigner and author of the group's Severn Barrage Report: "The Sustainable Development Commission is saying that the Severn Barrage would be a flagship project - leading the UK's investment in renewable energy. Yet to seriously damage an internationally important wildlife site in order to generate less than one percent of the UK's energy consumption is not the way to lead the world in sustainable development.
"We urgently need to promote renewable energy initiatives but they need to be the right ones. A combination of large offshore tidal lagoons, possibly in combination with a Shoots barrage or barrier, could produce more energy with more flexibility at much less cost and environmental damage. That's why we propose that such schemes are considered in any further Severn studies, as an alternative to the Severn barrage."



Chris Witts, Severn historian: "It's man playing with nature on too big a scale, without knowing the implications. I'm worried that we won't be able to turn the clock back if it goes wrong. We would lose the Severn Bore, which is a major attraction and the largest bore in Europe. That, to me, is short-sighted.


"Back in the 1960s, the Bristol Channel would be black at night. Now it's lit up like a Christmas tree - unbelievable light pollution. Are we really going to ruin the river to pay for things like that?"


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