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Severn reef better than a barrage

Last modified: 26 November 2008

Dunlin flock flying over Taff Estuary, Cardiff Bay

A new tidal power scheme could safeguard wildlife and generate more clean energy from the Severn Estuary than a 10-mile barrage, a report says.

A tidal reef, a longer dam, further downstream, would be less costly than a Cardiff to Weston barrage and keep intact most of the estuary's saltmarshes and mudflats on which at least 68,000 birds feed in winter.

The reef would operate for longer and have more underwater turbines than a conventional barrage, but turbines would be slower moving, minimising the danger to migrating salmon and eels.

Professor Rod Rainey of engineering consultants, Atkins, who authored the report, said: 'We believe this scheme could be more powerful but less costly than other plans being put forward, particularly the Cardiff to Weston barrage.'

'A tidal reef could rein in that damage, cost the taxpayer much less and be built more quickly'

The government wants to use the 45-foot tidal range of the Severn – the difference between low and high tides - to generate electricity to cut the UK's carbon emissions.

Ministers are to shortlist some of the 10 proposals for the Severn next month and the tidal reef and Cardiff-Weston barrage are among those being considered. The RSPB fears the reef will be dropped from the list because its design is untested.

The new study by Atkins, Europe's largest firm of consulting engineers, was commissioned by the RSPB to look at the feasibility of tidal reef technology, its energy generating potential and its cost.

Atkins drew four major conclusions:

  • That the technology behind a conventional barrage could be used to build a tidal reef;
  • That a tidal reef could generate more energy than the conventional barrage;
  • That a tidal reef would cost £2 billion less than the Cardiff-Weston barrage;
  • That a tidal reef could be designed within the government's target date.

The tidal reef proposal has been submitted to the government by Evans Engineering, a company based in Cornwall that designs and builds innovative renewable energy systems.

The reef would stretch 12 miles from Minehead in Somerset to Aberthaw, in the Vale of Glamorgan.

It could open at set points to allow large container ships to pass and be built in sections, enabling the much earlier generation of power.

Enormous potential

Rupert Evans, of Evans Engineering, said: 'The potential of a tidal reef is enormous. As well as electricity, it could produce hydrogen for use in non-polluting cars or the gas network. Its construction would mean far less road traffic because of rail connections, and would require less material and cost significantly less than other tidal options or nuclear power.

'It would cut Britain's carbon emissions by around 12 million tons annually, create more than 30,000 jobs during construction and give a global lead for local manufacturing companies, particularly in the marine engineering sector.

'Other schemes either defy the laws of Europe and would result in years of litigation, and some even defy the laws of physics and simply wouldn't work.'

Dr Mark Avery, Director of Conservation at the RSPB, said: 'The government must crack the problem of how to use the Severn's tidal power without harming its wildlife.

'We already know a Cardiff-Weston barrage would cost far more than almost any other form of green energy and seriously damage sites protected by law.

'A tidal reef could rein in that damage, cost the taxpayer much less and be built more quickly. Ministers should look seriously at the enormous pitfalls of a conventional barrage and the potential for using the Severn's tidal energy in a much better way.'

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Severn Barrage: Feasibility of 'Tidal Reef' Scheme (661Kb)
This report was produced by Atkins Ltd. for the RSPB. The RSPB have approached Atkins for advice on the technical and economic feasibility of the 'Tidal Reef' concept designed by Evans Engineering.

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