Will the Severn tidal barrage ever be constructed?

Balancing local and global arguments

The debate over the construction of a tidal barrage in the Severn Estuary between England and Wales is a textbook example on how difficult it can sometimes be to balance local and global environmental issues.

The Severn Estuary, located between the English city of Bristol and the Welsh city of Cardiff, has the second largest tidal range in the world — about 15 metres. It is exceeded only by the Bay of Fundy in Canada. This makes it the ideal place to build a tidal barrage for generating electricity. A 16 kilometre barrier between Brean Down (England) and Lavernock Point (Wales) could have a massive capacity of 8,640 MW during flow, or 2,000 MW on average. This is 5% of the UK’s projected energy needs by 2020.

A long history of plans

The idea of building a barrage in the Severn Estuary is not new. The first proposals date back as far as the 1840s. At that time it was based on the desire for a large shipping harbour, a railway crossing, and flood protection. The first official study to generate electricity by a tidal barrage was made in 1925. The capacity under consideration at that time was 800 MW. Since then, several new projects have been proposed, all of which were rejected on economic grounds. The project currently under discussion was first presented by the Severn Tidal Power Group in 1989. Margaret Thatcher’s government shelved the plans, but the recent demand for renewable energy, pushed by the alarming signals of global warming, has put it on the political agenda once more. The UK government is aiming to generate 20% of Britain’s energy needs using renewable sources by 2020.

A protected area

In April 2006, Welsh First Minister Rhodri Morgan and Secretary Peter Hain backed the plans for building the barrage. But in July, the UK government, by means of an Energy Review, advised caution and urged further research of tidal technologies, the environmental impact, and public acceptability.

The estuary is an important area for wildlife, in particular waders, and has numerous protected areas, including several National Nature Reserves. At low tide, large parts of the channel become mud flats due to the estuary’s extreme tidal range. It is estimated that around 80,000 waterfowl use the Estuary as feeding grounds in winter. The majority of them ‘will have to go elsewhere or perish’, according to Tim Stowe of the Royal Society for Protection of Birds.

The Severn also hosts a rare natural phenomenon: the Severn Bore. At the rising of the tide, water is funnelled up the estuary in a wave up to 2 metres high that travels in a spectacular rush upstream against the river current. This phenomenon, which exists in only a few places in the world, attracts a large audience. Some enthusiasts even attempt to surf the wave. It would disappear or at least be drastically reduced by the tidal barrage.

References:

• BBC News item, 6 March 2003, 'Vision for Severn tidal energy'
• BBC News item, 21 April 2006, 'Backing for Severn barrage power'
• Guardian news item, 26 April 2006, 'Estuary enery plan makes waves'
• BBC News item, 12 July 2006, 'Energy review urges barrage study'
• Earthtoys review, April 2006, Tidal Energy Update