I grew up in Bridgwater, Somerset, a town on the muddy banks of the River Parrett that flows out into the muddy expanses of the Severn Estuary. The Severn Estuary is famous for its huge tidal range (peaking at 13m) and for it tidal bore and consequently the Parrett also has a high tidal range and its own (somewhat smaller) bore which I did actually get to see once. Even when I lived in that region (and I am talking 25-30 years ago) there was talk of building a tidal barrage across the Severn to generate electricity and although no such barrage has been built, the idea of building one resurfaces from time to time and is particularly topical in our current fossil fuel dependent world.
Predictably, the idea of building a tidal barrage across the Severn is controversial, particularly in terms of the impact of any such scheme on wildlife and ecosystems and so whilst the environmental lobby might be expected to support such a scheme to generate energy from a renewable source, the environmental lobby might also be expected to oppose a scheme. This conflict is nicely set out in a recent article in New Scientist, Issue 2704 [18 April 2009]. Do we go for large schemes that generate lots of power but have obvious big impacts on the environment or do we stick with small schemes to minimise impacts but end up without much gain in energy generation or is there a middle ground? This is a question that is going to keep cropping up and my gut instinct is that there isn’t a one-size-fits-all answer.
Tim O'Hare 
I think it is possible to produce a good compromise with a ‘Tidal Reef’ from Minehead to Aberthaw or even further to the west, that only requires a two metre head difference. Treated by many including New Scientist as being somewhat ‘unusual’, it now has the support of six major enviromnmental groups with a combined membership of about 8 million members. The RSPB commissioned W.S.Atkins to look at the project in more detail, and I am happy to say that they and several other leading accademics agree that such a project could produce as much or even more power than the Cardiff-Weston barrage but without the environmental impact. Game, set and match?