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 News

Barrage may increase Severn flood risk, warns Stop the Barrage NOW campaign

10/10/08

As more maritime experts including the Gloucester Harbour Trustees join the Stop the Barrage NOW campaign, the expanding coalition is warning that a Severn barrage is likely to increase the risk of flooding in a region already badly affected by floods over the last 18 months.

Their warning is based on detailed scientific studies, which have found that estuarial barriers create considerably greater risks of flooding and siltation than were thought likely when the Severn barrage was first evaluated in the 1980s.

With some three million people living around the Severn estuary, and sea levels predicted to rise due to global warming, flood risk is already a major concern across the region.

The flooding and siltation issue was examined in a paper presented to a renewable energy symposium in Cardiff last month, by Roger Morris, Senior Specialist (Ports & Estuaries) from Natural England.

Morris has compared the potential impact of a Severn barrage with the Eastern Schelde storm surge barrier in Holland, which he believes offers many similarities to the environment of the Severn. Far from improving flood defences, he suggests that the evidence shows a barrage has the opposite effect, lowering foreshores and increasing the flood plains on either side of the estuary.

Niels Westberg, Marine Director at Bristol Port Company, has carried out his own investigations on the effects: “Quite contrary to earlier projections it is now clear from our own work and deep understanding of the estuary’s composition and water movement that there is a significant future threat from coastal erosion caused by wave attack should a barrage be built.”

The REA paper says that: “If erosion patterns in any way mirror those experienced on the Eastern Schelde, the long term impacts on flood defences and associated coastal infrastructure within the Severn estuary will place an increasing burden on flood risk budgets."

According to Stop the Barrage NOW, this is only one of several reasons why a barrage is not a viable proposition. It will also, they say:
• cost at least £15 billion
• produce energy for no more than six hours in every 24, costing twice as much as wind power and which will not come on stream until nearly 2020.

Campaigners are asking people concerned about the impact of a barrage to sign their petition to stop any further money being spent.

Instead, they are calling for further research into alternative renewable solutions in the estuary such as the possible development of tidal stream generators which can be placed safely and unobtrusively in locations where they can provide all the benefits of renewable energy without the huge cost and intrusive nature of a fixed barrage.

Notes to editors
1. The accompanying photo shows salt marsh erosion in the eastern Schelde. Photo provided courtesy of Eric van Zanten.

2. The paper referred to is: “A Severn barrage – planning for environmental consequences”, presentation for the Renewable Energy Association Wave and Tidal technologies Symposium, 23 September 2008, Cardiff, by Roger Morris, Senior Specialist (Ports & Estuaries), Natural England.

3. Key findings of the paper
The paper dismisses the only major barrage currently operating to produce tidal energy, La Rance in Northern France, as a poor comparative example, as its hard rock geology and sandy sediment are completely different from conditions found in the Severn.

It states that the Bay of Fundy in Northern Canada, which has the largest tidal range in the world and is the site of a tidal barrage, only provides a partial model. Larry Hildebrand from Canada's Environment Agency told a recent meeting of the Severn Estuary Forum that, after extensive studies, the damage to wildlife in the Bay of Fundy stopped any further tidal energy barrage from proceeding.

The comparator used mainly the Eastern Schelde storm surge barrier in Holland though it does not generate electricity. However, it is believed that it offers many similarities to the hostile environment that exists in the Severn. Far from improving flood defences as supporters of the barrage claim, the paper concludes that the evidence shows the opposite.

A physical barrier the size of the proposed Cardiff to Weston barrage would in effect create a giant reservoir behind the barrage and would reduce the tidal range by as much as half. The Severn’s high levels of suspended sediment - fine grained mud and sand, which feeds the mudflats and salt marshes - would start to settle in different places, further reducing water levels and flattening existing sand bars.

"Wind energy” imparted on the water behind the barrage will turn it into a very effective long term battering ram as waves hit the shore and mobilise the sediment.

The paper says that: “Because the energy left is so much reduced, this sediment will continue to settle rapidly, creating yet more erosion by lowering foreshores and increasing the flood plains on either side of the estuary.”

Whilst accepting that the Eastern Schelde barrier exists in a much smaller tidal range, he reports that Dutch scientists have observed serious erosion caused by sustained wave attack.

The paper concludes: “If erosion patterns in any way mirror those experienced on the Eastern Schelde, the long term impacts on flood defences and associated coastal infrastructure within the Severn Estuary will place an increasing burden on flood risk budgets".

About Stop the Barrage NOW
Stop the Barrage NOW is a collation of organisations and individuals campaigning to persuade the Government to focus on alternative tidal energy schemes in the estuary. Over the next few months the campaign will be lobbying to persuade the Government and the Department for Business, Enterprise and Regulatory Reform (BERR) that a barrage is not economically or environmentally viable. Campaigners want any form of barrage to be excluded from a shortlist of proposals to generate renewable energy from the Severn, due to be published in November.

Anyone who would like more information should visit the Stop the Barrage Now website at www.stopthebarrage.com

For further information please contact:
Katrina James or Debbie Smith, Stop the Barrage press office
Tel: 0117 317 8117 or 07843 087 861(Katrina) 07778790015 (Debbie)
Email: katrina@stopthebarrage.com debbie@stopthebarrage.com

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