The Sustainable Development Commission states that, because of siltation, a Severn barrage could lose half its capacity within just 10 years. The Government defines renewable energy as being inexhaustible. Can a barrage across the Severn be described as producing “renewable” energy if it “uses up” the resource, which is the funnel shaped estuary?
Government studies show that silty estuaries are not suitable for tidal range storage schemes like barrages and lagoons. In Canada, where similar schemes have been tried, whole estuaries have been become blocked with vast expanses of mud. How long could the Severn estuary produce power in this state?
If the Severn flowed with crystal clear water like La Rance in France, then a barrage might work. But La Rance’s geology is totally different with tidal power produced in an estuary with steep granite sides. Even so, silting problems here have meant this pilot scheme has not been rolled out.
Learning from a costly Canadian mistake
Prof Simon Haslett from Newport University has studied the Severn for over ten years, he said:
“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.
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 mud and it sticks
Dr Graham Daborn, a world-leading expert on estuaries, points out that estuarine silt can’t be modelled in the same way as sand - a non-sticky grain. As a living thing containing mini molluscs, bacteria and worms, silt deposits are stickier than sand and do not simply wash away. In fact, silt accumulations could be around 80 times stronger than traditional modelling predicts. He states that, “such accumulations would quickly fill up an estuary”.
The harnessing of truly renewable energy is possible in the Severn using tidal stream turbines. These are devices placed in the tidal current a little like underwater windmills. Canada is already embracing this leading edge technology in the Bay of Fundy - with turbines produced right here in the UK! The latest tidal stream devices are perfect for the shallow Severn.
To continue down the blinkered path of barrages and tidal storage solutions is fruitless. Not only is it exorbitantly expensive for the UK taxpayer, it is unlikely to work for long, it will destroy an irreplaceable resource and leave an indelible scar on our landscape. We need to help our Government embrace more effective, lower impact and truly renewable technologies.
Save Our Severn