It's a Bore. But for how much longer?

 
The plan to build a barrage across the River Severn and thereby harness the tide to generate up to 5% of the UK's electricity needs edges closer to formal acceptance. The plans are to be the subject of a public consultation, with a final decision taken by 2010.

If the barrage gets the green light (no pun intended), it'll be the world's biggest-ever renewable energy project at what is surely a conservative estimate of £20bn.

The barrage is motivated by good intentions. It's high time we looked for renewable energy resources, and the tide is about as renewable as it gets. But there's a downside. Building a barrage will inevitably decimate the habitats of the river's denizens. And it'll also ruin the Severn Bore.

The Bore is a magical, wondrous freak of nature. I've only surfed it the once but I'll never forget it. There are surfers who live their lives around the Bore, and their lives, too, will be shattered if the barrage is built.

What should surfers think about building the barrage?

Comments

[Matt]

Alex, It would be a great shame to lose a natural phenomenon. But, come on! 'Lives shattered'? So a handful of surfers will have to find something else to do once in a while, but it's for the greater good, which all surfers should be interested in.

What's more, man's quest for a better life will always have an environmental cost, even if it is in our own interest to minimise it. Weigh up and compare those of a coal fired power station and those of a barrage on the Severn.

Now, hundreds of thousands of people out of work in the worst economic downturn since WW2. If you're unfortunate enough to be one of them, that's life shattering.

Get well soon!

[Alex Wade]

Hi Matt,

You're right - 'lives shattered' was a bit OTT. I was thinking of some of the guys I met who live up there and centre their lives around surfing the Bore. However, in the current climate, there is worse on the horizon than missing a few waves.

Alex

[Richard]

Can someone provide a link to analysis of the effect the Barrage will have on upstream silting? How long will it be before the lake created will silt up and the barage become useless?
PS; why not put one across the Thames estuary?! I am sure no-one would complain about loosing that ecosystem would they?

[Neil Law]

The fact is that it can be done . And we don't need a bloody great wall across the river to do it. Tidal stream turbines are now capable of operating in shallow locations, and some of the new designs can be entirely submerged. I sought an opinion from a Canadian academic who has extensively studied the after-effects of barrage construction. He believes that La Rance, the barrage often held up as an example of what is possible, is simply not the way things will go with the Severn, because that river generates little or no silt. Siltation is likely to form OUTSIDE the barrage in the Severn, and it will stick, as it did at both Moncton and Windsor in the Bay of Fundy. It won't shift, and indeed, the experience of those disasters suggests that once this cycle of siltation starts, even if you remove the cause it can be very difficult to stop. It's not really a question of habitat vs energy, it's more a case of "why are we looking to a redundant technology, which won't work here".

The Feb tides were brilliant, by the way.

[Neil Law]

Note on siltation: Most severe siltation is most likely to be at it's worst on the OUTSIDE of any barrage structure, due to the source of the materials. The fluvial silt load is in the region of 500,000 tonnes per year according to to Prof Simon Haslett. The estuary holds around 10 million tonnes of it in suspension at any one time. This forms a layer of liquid mud approx 1 metre thick at slack tide, at the lower end of the water column, which is re-suspended when the tide begins to flow again. However, when silt of the type we have in the Severn settles and is allowed to dry, it becomes 80 times more resistant to erosion than other deposits. It is this difference in the nature of the silt which appears to be off the radar of the consultants at the moment. The silt transport models they use are normally based on sands and gravels, not materials with strong adhesive properties.

[Richard]

Thanks, more on silting etc at saveoursevern.org.
Another thought; this project is to help save the environment.
Given that 1 cubic metre of concrete liberates approx 500lbs of CO2 (approx = CO2 reduction by changing 10 tungsten lightbulbs to low energy bulbs) how many times over will we have to replace every tungstan light bulb in the country to balance the CO2 emmisions of the ? billions of cubic metres of concrete needed to build the Barrage?