Examination of Witnesses (Questions 60-67)
Dr Tom Shaw
31 MARCH 2008
Q60 Lord Rowe-Beddoe: Thank you.
I would like to be educated, if it is not the second largest,
then what is the second largest?
Dr Shaw: The second largest is an inlet
on the Hudson Bay in north-west Canada. Ungava Bay has the second
highest tide range in the world, following the Bay of Fundy. The
Canadians are first and second.
Q61 Lord Rowe-Beddoe: Well, there
has been a lot of misinformation on that score, thank you. The
two things I would like you to comment on, if you would: the economic
benefits to the south-west and to Wales, manifested by the differences,
as I understand it, in what was the 1988/1989 plans, namely both
a road and a rail link that will go across the barrage, which
will obviously obviate traffic having to go all the way up into
Bristol and so on, so perhaps you could comment on that. The other
thing is complementarity, if you have a barrage, you can still
utilise the tide and the wind further out, as I understand it,
is that correct?
Dr Shaw: That is correct.
Q62 Lord Rowe-Beddoe: So it is not
either a barrage or an underwater turbine, it can be everything.
Dr Shaw: Yes, the currents anywhere in
the estuary are dependent on where in the estuary one is considering,
and how much of the estuary, in terms of the movement of water,
is reduced by the presence of the barrage. So the further seaward
in the Bristol Channel, for example off Swansea, I think the effect
on currents would be minimal off Swansea, so that far seaward,
there would be little adverse interaction between the two. In
terms of economic implications, I find it a terribly difficult
issue to grasp what the responsiveness of commerce and society
in general would be if there was such a facility, albeit built
for power generation, but with the transport opportunities to
which you refer. How would we respond to this? The 1989 investigation
gave some guidance on that, with advice from a number of consultants
professional in that sector, and the opportunity is very, very
considerable. This may be flippant, forgive me, My Lord Chairman,
but to the point that one says, well, when you build a barrage
for all these other reasons, do not forget to put in the turbines!
They will help too. I think there is an element of significance
in that, but the balance between the two, I think, is still open
to debate.
Lord Rowe-Beddoe: One more?
Q63 Chairman: Please, yes. I think
just before that question, could you, for the neophytes on this
Committee, just explain the difference between the barrage and
the turbine?
Dr Shaw: Oh, sorry, apologies. Well,
a barrage, per se, is essentially a dam with holes, through which
water flows to the propellers, which are the turbines, and the
turbines in this case are like wind turbines, only they have very
wide blades, four or five on a rotor. These rotors may be, in
terms of the height of this room, a radius of almost twice the
height of this room. I mean, they are big, they are typically
10 metres in diameter, not twice the height but pushing twice
the height of this room. They rotate quite slowly, not surprisingly,
because of their enormous size and very wide blades. They are
very standard machines, and what is proposed for the Severn Estuary
is not the biggest by any means in the world, they have been built
to that geometry and size now, I suppose, for the past 50 years.
The Rance Barrage in Brittany, near St Malo, has 24 machines of
this type, smaller than would be appropriate for the Severn, and
they were installed from 1965-7. The same machines, working in
seawater, of course, are in place today, they have not been changed,
the blades are as they were originally after 41 years and a bit,
and what is almost uncanny, but I think it is true, is that the
predicted annual energy output from the Rance Barrage when it
was being designed in the late 50s and early 60s is what has been
achieved almost every year since then, and is still being achieved.
It is very simple technology, My Lord Chairman, hydroelectric
power is not very demanding, and it is certainly not demanding
in the context of tidal power, now that the issue of salinity,
which was an issue, does not seem to have arisen, it has been
dealt with through cathodic protection.
Chairman: Thank you. The Committee either
hopes to visit St Malo or at least take evidence from EDF, I think
it is, who is responsible. Lord Rowe-Beddoe?
Q64 Lord Rowe-Beddoe: Yes, just leading
on from an earlier question, the concerns of the environmental
bodies. I believe the Sustainable Development Commission reported
on this quite recently, and is it correct that on balance, they
came—I will not put words into your mouth, how do you think
that they reported?
Dr Shaw: Well, I think they reflected
the concern that was put before them by organisations like the
Environment Agency and the RSPB, and I think that was their job,
to report on what they had been told. But there is, Lord Rowe-Beddoe,
to me, a key issue here, and it is one which has not really seriously
been addressed, but I am sure it will be now with the current
Government investigation, and that is: if there is real justification
for concern, can something be done to ameliorate it? That interaction
has really yet to take off. The Sustainable Development Commission
and the Environment Agency and others now frequently quote the
need for compensatory habitats, or in some cases the impossibility
of providing compensatory habitats, because of the scale of the
compensation that the barrage would require. That is one side
of the argument. But there is a counter argument that says that
the habitats that would be created as a consequence of the Severn
Barrage are such that the barrage could be used as a means of
offsetting other developments, for example off the coast of Norfolk,
where compensatory habitats would be required to counter so-called
managed retreat of the coastline, that the benefits that the barrage
would bring to the habitats of the Severn Estuary could be used
in that compensatory way. So here are diametrically opposite views,
and I think to me the significance of the fact that there are
diametrically opposite views is because the truth has not been
established, at least not convincingly established.
Q65 Lord Dykes: Coming back to the
comparison with Rance, and I appreciate there are many physical
and other differences between them. We are told on good authority,
I think, speaking from memory, that the water movement is only
one way now. They did intend it to be two ways at the beginning.
Are you implying that the Severn Barrage would be two-way and
therefore would increase the generation capacity from that point
of view? Do you still think that would be so?
Dr Shaw: The French, when they designed
Rance—I will not say they did not know which to favour,
but Rance was built as a pilot scheme for a project on the scale
of the Severn Barrage, at the les de Chausey on the west coast
of the Cherbourg peninsula. It was a model, a big model, but it
was a pioneering development which needed to sort out such issues
as one-way generation, ebb or flood, or both ways, ebb and flood,
going in both directions; together with another, to me extremely
important, feature as well, the opportunity to use those same
turbines as pumps around the time of either high tide, when you
increase the basin level by pumping a large amount of water through
not much height, or lowering it, around the time of low tide,
and so the Rance Barrage includes all four modes of operation.
Those modes were tested for maybe the following ten years, through
the 1970s and even the 1980s, but now it is almost totally ebb
generation. It generates in one direction, from high basin level,
following high tide, it generates seaward only, and it pumps around
the time of high tide to raise the level of the basin. Forgive
me, My Lord Chairman, I am trying to avoid a lecture on this:
there is a fundamental issue that in generating, the level of
the basin, if I can call it the basin, on the landward side of
the barrage, what you are left with is inevitably that much higher
than the lowest level to which the other side falls, so if you
only generate in the ebb direction, your basin level at the lowest
is only about mid tide level now. If you generate in any other
direction, your highest level is only about mid tide level now,
if you generate on the flood direction. So the issue of consequential
water levels in the basin area to me is absolutely crucial. Whether
it is the environment or whether it is shipping or whatever it
may be, all of these consequences of the barrage and the way it
is operated will need to be given very serious consideration.
The Rance Barrage is now ebb generation almost entirely, with
flood tide pumping, and that, to me, environmentally, is the preferred
solution. Can I just, forgive me, disagree with what I understood
you to say in your opening comments? I think there is very strong
similarity between the Rance Estuary and the Severn, very strong.
In fact, I say it is very, very strong, so much so that the comparisons
that have been made between the two are really quite powerful.
Q66 Lord Dykes: May I, My Lord Chairman,
just very quickly? You mentioned the optimal locational suggestion
as being west of Weston-super-Mare and west of Cardiff. Are there
still members of the pro-barrage lobby who are also advocating
that one does that, as well as a much smaller one at the top end,
the beginning of the river itself, rather than the estuary, to
actually have double the opportunity, even though it is not double
the capacity?
Dr Shaw: No, sadly, as I understand it,
it does not work that way. As I said just now about the residual
water level that is left in the basin area following generation,
whatever form of generation one uses, that is all that the other
barrage further upstream would have available to it. If you build
another barrage, a smaller one, further up the estuary, so to
speak, then you will be denying the larger one some of its generating
potential, and you will gain less than you lost by having a second
scheme. So there is, I think, no merit that I can see from having
two in the same estuary.
Q67 Lord Dykes: Thank you very much
indeed. And finally, may I, My Lord Chairman, very quickly? On
the putative economic matters, would there be any possibility
of spectacular visitor and tourist infrastructure on top of the
barrage being so considerable and enormous that it would actually
offset some of the initial building costs?
Dr Shaw: My Lord, that was rather the
gist of my comments earlier, how enormous is this enormous to
be? The Rance Barrage is said, I believe it is true, to be the
most visited industrial facility in France. The Severn Barrage,
wherever it is, would be on or very close to popular tourist routes
up and down the M5, and to the west on the M4, west of Cardiff,
and to me, it is incomprehensible to imagine that it would not
be popular, if it was properly presented, which surely it would
be. But the Rance visitor facility, if you have not seen it, is
worthwhile. It is impressive, even though the scale is relatively
small. I should say, My Lord Chairman, if I may, that the difference
between one barrage and another barrage is essentially length;
not height or width, but length. The Rance Barrage is half a kilometre
long, and the Severn Barrage would be roughly 30 times as long,
but it would be just more of the same, 15 kilometres.
Lord Dykes: Thank you.
Chairman: Forgive the pun, but I think
you have whetted our appetite to visit the Rance Barrage, so thank
you very much indeed. We are going to take a pause now, but the
Committee is indebted to you. Thank you.
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