Report slams Severn barrage study

Four leading conservation groups have condemned a government report on potential technologies for harnessing the tidal power of the Severn Estuary as biased, following the commissioning of their own engineering study.

The National Trust, RSPB, WWF and the Anglers' Trust accuse the report of overlooking the advantages of smaller-scale coastal lagoons and favouring proposals for a £12bn barrage scheme, which they fear would halve the Severn's tidal range and have a huge impact on local habitats.

In January, the Department of Energy and Climate Change (DECC) shortlisted five tidal energy schemes for the Severn, which it said could provide up to five per cent of the UK's electricity needs.

Controversially, the shortlist rejected all proposals based on lagoon technology, although the government did announce £500m worth of funding to keep the option on the table.

The decision to exclude lagoon technologies from the shortlist angered conservation groups and prompted them to commission their own viability study from engineering consultancy Atkins.

The NGO group says that the study reveals "several serious shortcomings in the [original study's] power calculations which bias the shortlisting process".

It also says the methodology and outcomes of the the original government report – carried out by engineering firm Parsons Brinckerhoff – were insufficient to adequately identify a shortlist of tidal power options for the Estuary.

The coalition – which also found that the study had used 30-year-old data – concluded that the cost and risk of larger schemes may have been underestimated. It also said that the power capabilities of smaller tidal energy schemes had been underestimated – a claim long made by Friends of the Earth.

It is now calling on the government to abandon the current shortlist and start the whole process from scratch.

Martin Harper, head of sustainable development at the RSPB, said the government did not need to make a rushed decision. "As this review shows, that could mean unnecessary damage to the environment, an oversized bill for the taxpayer and all for less electricity than is possible," he said.

"We have a real opportunity to build something on the Severn which becomes the gold standard for environmentally friendly tidal power and a template for other schemes around the world."

A spokesman for DECC said all technically feasible schemes had been shortlisted.

"The door's not closed to less developed technologies like tidal reefs and fences; in fact, we're putting £500,000 into studying them, but they could be decades away from commercial deployment," he said.