BS: Disastrous effect of Severn barrage

Subject: BS: Disastrous effect of Severn barrage
From: greg stephens
Date: 06 Oct 07 - 06:15 AM

Tidal energy is commonly thought of as some kind of free renewable stuff. I don't think it is, but I don't have the physics to figure out just what's going on. It's something to do with the gravitational linkage between the earth and the moon. Could anybody enlighten us? I have a feeling that building a barrage across the Severn, or Morecambe Bay or whatever, may well not only slow up the earth's orbit, but also pull the moon down on our heads. Is this true? And, perhaps more to the point, how quickly will it happen?

Subject: RE: BS: Disastrous effect of Severn barrage
From: McGrath of Harlow
Date: 06 Oct 07 - 07:08 AM

I read that letter in the Guardian Technology weekly too. (Watery grave for Earth - scroll down to see the letter.) I think it's basically tosh.

True enough, there'd be a slowing down effect, but then the same is true when a fly hits the windscreen of the car we are driving. I'm pretty sure there's no need to worry too much about it.

Subject: RE: BS: Disastrous effect of Severn barrage
From: Mr Red
Date: 06 Oct 07 - 07:12 AM

Hey Greg
If 'n when the moon pays a visit we will solve the world food shortage - let 'em eat green cheese.
I doubt it will have an effect on the moon unless you intend to be around a few hundred million years and a stray asteroid couild do that far more catastrphically.
The worst effects are the inevitable silting of the estuary above the barrage, there would be no Severn Bore, and wildlife would change as the Severn reduced in salinity &/or increased in polution. The inevitable motorway on the causeway would effect the landside wildlife by disturbing the birds etc and also on Flat Holme and Steep Holme (verboten to all but a few) - because that's the most likely route for a barrage.

Subject: RE: BS: Disastrous effect of Severn barrage
From: Geoff the Duck
Date: 06 Oct 07 - 07:25 AM

The main idea of a tidal barrage (for elecric) is that it doesn't actually stop the water flow, it just pushes it through smaller holes with turbines which remove a small amount of the energy of the moving water. General idea for something such as Severn Barrage is that it works with water going both ways.
The physics on a global scale is that it is an increadibly tiny amount of water compared with the total sloshing about in the oceans, so any global effect is about the same as a butterfly flapping its wings in Japan.
I was at university in Cardiff around 1981 when they were first proposing the Severn barrage idea. We looked at some of the possible effects, and the most likely ones related to changes in deposition of silt. The Severn is, in places, a very brown river. The result of water stirring up and carrying with it, large amounts of silt and fine sand. As long as the water is moving rapidly and swirling about, the silt will remain suspended. If you slow the flow, the heavier particles are likely to settle out and might mean that certain places will become mud or sand banks which weren't there before.
Depending on if and where this happens, it could cause local problems, possibly for wading birds which feed in the estuary (is it Slimbridge wildfowl thrust down on the Bristol side of the channel?). Certainly it is a major European bird site.

I haven't seen any up to date information or research on the area, so don't know what current thoughts on the subject are, but that was the thought at that time.
Quack!
GtD.

Subject: RE: BS: Disastrous effect of Severn barrage
From: Ron Davies
Date: 06 Oct 07 - 08:21 AM

I was trying to figure out exactly what Severn said when he was over in the UK to cause this dire result. He is a ferocious punster but......

Subject: RE: BS: Disastrous effect of Severn barrage
From: jeffp
Date: 06 Oct 07 - 09:29 AM

The tides don't pull the moon. The moon pulls the tides. With a lot more force than anything built by man can stop. Remember Canute.

Subject: RE: BS: Disastrous effect of Severn barrage
From: McGrath of Harlow
Date: 06 Oct 07 - 09:59 AM

"The tides don't pull the moon. The moon pulls the tides." Well of course, they each pull each other, in accordance with Newton's Third Law of Motion: "For every action there is an equal and opposite reaction."

But it's going to take an awfully long time for there to be any significant effect. And our contribution to that kind of thing isn't liable to be too significant. It's of a different order from the impact of humans through CO2 production by burning up the Carbon stored over millions of years in a few decades, which is what we are doing now.

Subject: RE: BS: Disastrous effect of Severn barrage
From: Janie
Date: 06 Oct 07 - 10:02 AM

Me too, Ron:^)

Janie

Subject: RE: BS: Disastrous effect of Severn barrage
From: Uncle_DaveO
Date: 06 Oct 07 - 10:08 AM

I have a feeling that building a barrage across the Severn, or Morecambe Bay or whatever, may well not only slow up the earth's orbit, but also pull the moon down on our heads.

I see no likelihood that there would be any effect on the Earth's orbit, but the Earth's rotation might to some infinitesimal degree be affected.

Dave Oesterreich

Subject: RE: BS: Disastrous effect of Severn barrage
From: Micca
Date: 06 Oct 07 - 10:19 AM

Ok , So Severn is slightly Portly, but I wouldnt call it a "barrage", just a thickening at the waist!!!

Subject: RE: BS: Disastrous effect of Severn barrage
From: greg stephens
Date: 06 Oct 07 - 11:40 AM

Uncle DaveO: you're right, I did mean its spinning round itself, not its spinning round the sun. But I'm absolutely sure this extra energy generated by the barrage will have to be sourced from the interaction between the earth and the moon. But I can't figure out if that will make the moon fly off into space, or come crashing down on my head.My feeling is it will slow the moon down slightly, and that will cause it to come closer to us. But I'm not sure.

Subject: RE: BS: Disastrous effect of Severn barrage
From: greg stephens
Date: 06 Oct 07 - 11:49 AM

McGrath: you say it's going to take an awfully long time for it to have any significvant effect. Well, I can tell you I was driving home from a gig last night, and the moon was low down, very red, and to my unprofessional eye it looked a lot bigger than usual. And bigger means nearer, I reckon, not to mention "more means worse". And the fact is, they haven't even built the barrage yet, just a few little trial tidal bob-up-and-down thingies. Personally, I'd strengthen the roof of your house, never mind complacency.

Subject: RE: BS: Disastrous effect of Severn barrage
From: SINSULL
Date: 06 Oct 07 - 12:03 PM

Severn! Cellar!
Imagine causing a cataclysmic international disaster with one rampant post on Mudcat.
Shame on you!

Subject: RE: BS: Disastrous effect of Severn barrage
From: Uncle_DaveO
Date: 06 Oct 07 - 01:14 PM

Greg, the moon always looks bigger when nearer the horizon. Whether by the effect of the light coming through more of the atmosphere, or because there are objects to compare with it in size, I can't take an oath.

I'd vote for the latter, though.

Dave Oesterreich

Subject: RE: BS: Disastrous effect of Severn barrage
From: Rapparee
Date: 06 Oct 07 - 01:28 PM

It's not going to happen. The Earth's mass isn't changed so it's gravitational pull remains the same.

Yes, someday the Moon will crash into the Earth, but it won't be for a while yet. Two or three weeks, at least.

Subject: RE: BS: Disastrous effect of Severn barrage
From: Becca72
Date: 06 Oct 07 - 02:04 PM

Probably just after Sins gets the stink off Seamus, eh Rapaire?

Subject: RE: BS: Disastrous effect of Severn barrage
From: McGrath of Harlow
Date: 06 Oct 07 - 02:24 PM

The moon can certainly look most peculiar on nights when someone else is lined up to do the driving...

Subject: RE: BS: Disastrous effect of Severn barrage
From: folk1e
Date: 06 Oct 07 - 08:54 PM

Disastrous to who (or what)?
It would certainly create changes to the estuary, and may adversely affect some plants and animals!
On the other hand it would generate "free" electricity that was carbon neutral (after building costs). If this proved successful other similar barrages may be built causing a loss in share value of the Nuclear and fossil fueled generators of electricity. This could have a knock on effect with the big American petrochemical industries creating panic and wholescale redundancies! Is the price of Green "Free" Electricity worth it?
Now let's see ........ insert your choice of three lettered answer here (      )



As to the previous posts concerning gravitational effects ............ Why do you think the moon always faces the same way?
I suspect the Apollo Moon landings have had a greater effect (every action .... )

Subject: RE: BS: Disastrous effect of Severn barrage
From: Liz the Squeak
Date: 07 Oct 07 - 03:41 AM

Bring back water wheels.

LTS

Subject: RE: BS: Disastrous effect of Severn barrage
From: greg stephens
Date: 07 Oct 07 - 04:50 AM

McGrath: I resent the aspersions you cast on me. I was driving myself, and stone cold sober. You may laugh now, but you'll laugh on the other side of your face when chunks of burst moon come raining down on your computer.

Subject: RE: BS: Disastrous effect of Severn barrage
From: Mr Red
Date: 07 Oct 07 - 07:13 AM

I think there is a greter chance of the Moonies taking over the world. The real problem is that the world hasn't acknowledged the way things are going. Sure we take our recycled rubbish to the bins, in 4x4's and drive to the supermarket to get eco and fair trade groceries. But are we going to reduce our consumption of "power" until it gets expensive enough to be noticed?

Subject: RE: BS: Disastrous effect of Severn barrage
From: Uncle_DaveO
Date: 07 Oct 07 - 11:15 AM

Mr. Red, your answer is YES!

Dave Oesterreich

Subject: RE: BS: Disastrous effect of Severn barrage
From: GUEST,Jim Martin
Date: 07 Oct 07 - 08:04 PM

I read (or heard) somewhere, that tidal power is more efficient when only using the falling tide. Presumably, the water is stored (dammed in effect) and then released under control with greater velocity. So, in effect, the tide would go out a lot faster than coming in.

Does anyone know where this is already happening?

Subject: RE: BS: Disastrous effect of Severn barrage
From: GUEST,Oral B Roberts
Date: 08 Oct 07 - 04:13 AM

The effect of damning rivers will be to put out the fires of Hell. The wicked will go unpunished and Ryanair will start 10p trips there (plus tax). Celebrity Ninth Circle will appear on channel 4, will Satan get off with Jade?

By the way the moon is bigger near the horizon because it's cold in Outer Space, so it contracts. When it gets nearer the ground, it warms up and expands. If it came to earth on a hot day it might well pop.

Subject: RE: BS: Disastrous effect of Severn barrage
From: Ella who is Sooze
Date: 08 Oct 07 - 04:25 AM

I'm with LTS! Why can't they put water wheels in the Severn.

I went to see the Severn Bore recently - it would be no more if the barrage goes across. It's a shame - it's a part of nature, and lots of things would be affected if it is stopped.

Shame...

EWIS who lives next to the Severn...

ps. does anyone know of any public forum on it?

Subject: RE: BS: Disastrous effect of Severn barrage
From: MDSHydrosoils
Date: 08 Oct 07 - 05:37 AM

The Moon versus Le Barrage

Even George cannot exercise enough pull in Florida to Vote for a Moon relocation, it is more a case of whether the Barrage Makers can withold the Tidal flow and the slippery base rocks and soils (and the Flood 3 metres a second off Battery Point July 2007). And even Mugabe cannot Mine enough Moon to alter the progress of Zimbabwe.

I look forward to listing some Muddy Music for consideration as to listening power, which might have more effect. Mike

Subject: RE: BS: Disastrous effect of Severn barrage
From: McGrath of Harlow
Date: 08 Oct 07 - 06:30 PM

I rather like the idea of artificial atolls (or Dam-Atolls) as a way of extracting tidal energy. And we could get some interesting new places to live established in the process.

Subject: RE: BS: Disastrous effect of Severn barrage
From: GUEST,beachcomber
Date: 08 Oct 07 - 06:55 PM

If any one is worried about the pull of the moon on the tides in Wales or vice versa then they had better pray that we do not propose any similiar barrages here in Ireland. Nobody, but nobody uses "pull" as effectively as we do.

Subject: RE: BS: Disastrous effect of Severn barrage
From: GUEST,Fibula at work
Date: 09 Oct 07 - 06:30 AM

hmmmmm,
http://en.wikipedia.org/wiki/Marine_Current_Turbines
Strangford Lough's getting tidal turbines... does that count?