I wasn't just an objection from the RSPB which scuppered the Severn Barrage.
It wasn't actually cost-effective either, although DH was a firm advocate of the scheme and of tidal power.
October 2010:
Why was the Severn Barrage scrapped?
The high hopes for the colossal project were crushed on 18 October, when the UK’s Department of Energy and Climate Change (DECC) announced that the plug was being pulled in favour of pursuing other renewable options, as well as plans for new nuclear power generation. The announcement came after the Severn Tidal Power feasibility study reported that the project was comparatively high cost and high risk.
Chris Huhne, the UK Government’s Secretary of State for Energy and Climate Change, framed the cancellation as primarily a measure to safeguard taxpayers’ money. “The study clearly shows that there is no strategic case at this time for public funding of a scheme to generate energy in the Severn estuary. Other low carbon options represent a better deal for taxpayers and consumers,” he said in a statement.
^It was claimed that the Severn Barrage would be able to provide for around 5-6% of the country’s electricity needs.”
Indeed, from a pure cost perspective, the Severn Barrage always had the potential to become a white elephant.^
The sheer scale of the project, along with the vagueness of cost estimates (original estimates spanned a mind-boggling range of £2bn to £20bn, with the recent Severn study predicting that costs could even rise to £30bn), the DECC clearly decided that the upfront cost was disproportionate to the long-term (still largely unproven) benefits, especially during a period of fiscal austerity and massive funding cuts to frontline services.
Beyond problems of financing, the Severn Barrage scheme was controversial from the start due to the undeniable environmental impact that the project would have had on local eco-systems.
^Wildlife campaigners criticised the proposed barrage because it would have effectively halved the tidal range of the river, wreaking havoc on the salt marsh and mud flat feeding grounds of some 85,000 birds. As RSPB conservation Dr Mark Avery told edie.net in an interview back in 2006: “This is one of the most important sites in the UK for wild birds and the chances of them surviving if [the Severn Barrage] went ahead are fairly slim. There wouldn’t be enough room left for all the birds and there wouldn’t be enough food for those that remained.^"