A SCIENTIST from a leading university has discussed concerns about the planned Severn Barrage at a major environmental conference in Canada.

Prof Simon Haslett, head of heography in Bath Spa's school of science and the environment, says Canadian scientists are alarmed about the scheme from their own experience of harnessing tidal power. He warns that Britain should not make the same mistakes.

Prof Haslett was addressing the annual conference of the Atlantic Geoscience Society in Halifax, Nova Scotia. He gave a briefing on the UK government proposals, announced last month, to build a barrage across the Severn Estuary.

His presentation was part of a special session on Canada's own experiment with tidal power in the Bay of Fundy.This has the highest tidal range in the world, even higher than the Severn Estuary.

Canadian scientists at the conference told him the Bay of Fundy scheme had caused serious environmental damage, so they were shocked that a Severn Barrage was even being considered and urged the UK Government to think again.

Prof Haslett says Britain should take heed: "The Canadians have been experimenting with tidal power generation in the Bay of Fundy for many years, building a barrage across one of its tributaries as long ago as 1984.

"The consequences have convinced them that building a barrage is inefficient, has many undesirable environmental impacts, and is unsightly. The UK needs to learn from their experience and not make the same mistakes."

A tidal barrage was built across the Annapolis River and opened in 1984. According to Prof Haslett, the barrage has proved inefficient because it can only generate electricity on the falling tide, rather like hydroelectric power from reservoirs.

Similarly, the barrage acts like a dam, causing siltation of sediment and ponding of water upstream, which leads to infilling of the bay or estuary and the loss of tidal wetlands, such as salt marshes and mud flats. These are often used as feeding grounds by migratory birds, and even whales that swim through the sluice gates during a rising tide, get trapped behind the barrage and, in some cases, have died.

Prof Haslett says: "For the Canadians the idea of a barrage is now history and doesn't even get raised as an option during tidal power debates. It's so old hat they are amazed the UK is even considering it.

"The Canadians now only use turbines that are placed in the tidal stream, so that electricity is generated both on the falling and rising tide. Some turbines are submerged on the seabed, so you can't even see them - a bit like undersea wind farms."

Prof Haslett has researched and written extensively on the Severn Estuary over the last 10 years. He now wants to ensure that the UK does not make any hasty decisions.

"If the Canadians are right we shouldn't even waste any time and millions of pounds of taxpayers' money considering a barrage.We should perhaps move straight on to assessing other methods of generating electricity from the tides."