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A Few thoughts on the Severn Barrage

If you ever wondered what the severn barrage might consist of then this is a very good read

ETSU REPORT NO. T/09/00212/00/REP

Sir Robert McAlpine Limited
on behalf of
The Severn Tidal Power Group
( pretty lumpy for a dial up - 70 odd pages, about 400kb )

It was obviously a very costly and recent report, so you can bet your life it would carry a bit of weight in any proposed development.

Tidal Levels

Reading this and its decription of how the sluices would operate I've tried to sort out what the potential tidal levels would be.

I note, that nowhere in this report do they specifically quote a mean low water height. They focus a lot on the slightly lessened HW levels - and the implcations this has to improve flood defences upstream of the barrage.

You get a feel from this publication that many vested interests would be tagged on to this barrage - given it would be unlikely to be 100% centrally funded. Savings on flood defences upstream - especially with the potential for greater sea levels to come - and the prospect of a extra severn road link - easing traffic on an already worn out first Severn Bridge.

The daft thing is - and it does get a mention here - is what is really need is a new RAIL link - the Severn Tunnel has just about had it - but the problems of putting a rail crossing over locks big enough to handle the potential size of the vessles using Portbury seems insurmountable.

New Port ?

I get the feeling that if this ever comes to fruition - then new deep water port facilities will be built downstream - it being cheaper than providing massive locks. It is mentioned that encorporating large deep water locks is a huge logistical problem - as a passage has to kept open while the build is underway.

Also, the potential of the Avonmouth/Portbury site for housing, leisure waterside development is awsome - especially given a higher LW level and longer HW stand.

Potential Ranges/ Curves.

PDF page 21 of this report as online - cites potential generating flow patterns with regard to existing HW and LW tidal flows.

This appears to show a LW level held at approx half spring HW - about 6.5m

They also claim the max HW levels would be slightly less than at present - both above and below the barrage, with a few exceptions. HW level would obviously still fluctuate between the neap and spring heights - but the curve between the 'pegged' LW height and HW would be drastically altered.

From their scenario -

0hrs through to +3hrs HW - a HW stand, constant height.

+3hrs through to -4½HW - gradual, constant fall to pegged upstream LW level ( about 6.5m)

-4½hrs through to -3hrs - LW stand - constant height ( at pegged level)

-3hrs through to 0hrs - 'Normal rise' from 'half tide' ( pegged LW ) to HW for the day.

What this is doing essentially - is holding the HW level for three hours - then slowly releasing it at a constant rate right through the LW downstream of the barrage, up to about -4½HW - when generating stops and the LW level is pegged, at about 6.5m, for about 1½hrs - the seaward side 'catching up' on the level about -3hrs HW. Then a normal rise to the HW for the day.

A Few Bars and Restaurants half way

I also read of, ominously, - 'and its eight man made islands and four marinas' - we all know who will be in on the act for the marinas, Mr Crest N!- and wouldn't he like to get his hands on Avonmouth and Portbury site for development !


THE most important issue here would be free, 24hr access - as is the case with Cardiff. Even that has its drawbacks - ie, WHY can vessels not anchor in the enclosed Cardiff Bay ? - We all know why - in deference to the profits of the Marina and Quayside charges.

As soon as you have an 'enclosed area' - little people with pens to push love to start writing 'rules'.

This somehow is the most worrying thing of the whole potential venture - not the wildife, not the generating or the road links - the fact that you are "selling the Estuary" - to private capital, somehow. I don't see it anyones to sell - if anyone owns it, I do, - part share, as a taxpayer.

However, I fear that any private money in this is going to be rubbing its hands with glee that they have every leisure craft north of the barrage over a barrel for access.
I fear for a similar ban on anchoring within an enclosed upper barrage area - anything that can be done to enforce boats to use paid for facilities - once the sea conditions would make it easier to anchor off.

Don't forget out Feathered Friends

The environmental issues, of course, are going to be a major one - but I really doubt it will deter the developers one iota. As with all these things - the government will say ok if they feel there are any political 'brownie points' to make - then will happily pass it off to private development, so it costs them nothing, and whose only concern is profit

Actually - once constructed - I don't think it would particularly put off the wildfowl - after all, some of them are flying half way around the world to come here - I'm pretty sure they can cope with a few altered mudflats and a new concrete cliff to play on !

I do think wildlife is a little more adaptable than we give it credit for - doubtless many would disagree !

The disturbances caused 'under construction' however have to be huge. Consider that at present it is considered a disturbance to wildlife to dig a mooring sinker on the Axe, in the winter months !

Losing the Emptyness

If this ever goes ahead - it will be nothing short of a dramatic change to this area. It would certainly lose some of its 'unique' quality to the local sailor. Its common to go out all day. even on a holiday and hardly see another boat. The prospect of little tide, hence easier sea conditions, less range, longer HW stand will be either a blessing or a curse.

Should we lose an empty, wild open estuary - and if not, who are we saving it for ?
In reality, not many people go to the end of Brean Down to admire the view - 99% are in the bars and leisure facilities of Weston and Brean, Cardiff etc. They probably wouldn't even notice it had been built - and really, it would seem, not that many sail the area on a leisure basis at present.

It would destroy the 'sailing solitude' of the area - a potential max 'artificial' tidal stream of about 1 kt, plus less influence from down channel sea conditions - would tame the waters.

After all - it would not be open sea would it - it would be a lake. Probably still a choppy one - but less so.

I like the fact that when I'm alongside Steep Holm - I know that there is not a single thing except water between me and S America, or New York or wherever, if I cared to keep going and turn left, or right - Nice to know its an open road.

Some Day Maybe

So will it all happen ? - not quite yet, but I reckon its a cert at some point. So best I get all the sailing in I can around here - so I look back on it someday.

Just don't try charging me if I want to sail to Watchet !