Severn Barrage 3D model

[DataWizard223300]

The silty turbid water is quite possibly shown on the (correct) western side of the proposed barrage, where tidal activity continually stirs it up.

Anything "carried down" the rapidly moving Severn Riveer will tend to be larger particles than silt, and would drop out in the calmer impounded water.

[DataWizard223300]

The fundamental questions in respect of "silting up" seems to be:

(1) What is the capacity of the upstream tidal compound relative to the amount of material carried annually into it by the Severn?

(2) What will be the net movement of "silt" across any barrage (It is conceivable, for instance, that the net effect of daily tidal inrush could actually carry historically deposited material from outside the barrage INTO the upstream tidal compound)

[DataWizard223300]

Oh yes, AND, could any build up of silt be economically removed (albeit at some energy cost)!

It is not necessarily the case that if silt builds up it is impossible to remove.

[neilandfi]

I submitted a paper to the inquiry which focussed on siltation. The evidence I received suggested that there is at any one time around 500 million tonnes of materials in suspension, being replenished at a rate of 10 million tonnes per year, from the river itself, and via coastal erosion. Reducing the flow of the tide by half will reduce it's energy eight fold, and thereby reduce it's capacity to carry silt... leading to deposition. Due to the flood tide, this could happen inside OR outside.....

[neilandfi]

...OR outside the barrier. At present , the tide rushes in here at such a pace that it creates a large tidal bore. It recedes more slowly. According to Dr Graham Daborn, Acadia Centre for Estuarine Research, that will tend to mean a pattern of deposition similar to Moncton. So, yes, clogging up of the embayment, but also extensive filling in of the estuary outside the barrage. He told me that dredging will give rise to a need for further dredging. And the areas involved are huge, so go figure!

[amyleigh15]

where did you get the evidence about the '500 million tonnes of material in suspension.' i'm doing a short presentation at uni on the severn barrage and would like to quote that, but i need to check it's reliable first!

thanks =)

[neilandfi]

Happy to help. If memory serves, it was Prof Simon Haslett of Newport Uni.. find him on the net. The other academic you could do with checking out is Dr Graham Daborn, Acadia Centre for Estuarine Research. Also worth a google search of Dr Hubert Chanson's work.

[amyleigh15]

thank you, that's a real help! =)

[neilandfi]

I checked back on the original message I received informing me of that figure back in June this year. I'm wrong..VERY wrong. The correct figure from Prof Haslett is 10 million tonnes, replenished at a rate of 500,00 tonnes per year of new material. I have absolutely no idea how I managed to change that to a figure 50x greater! As a result, I will have to edit the content of one of my own youtube vids.

[neilandfi]

According to Prof Simon Haslett,the greatest turbidity is along the english shore, and further east towards the area of the Shoots proposal.

And you are incorrect about the materials carried by the river. Much of it originates from the keuper marls of Worcestershire, which is some of the heaviest clay in the country..very sticky, with very small particles. There is also a fair amount of coarse,sandy stuff which would originate from the rather soft rocks of Bewdley-Bridgnorth area.

[ukactive]

What a complete waste of time and more to the point TAXPAYERS money!!! Tidal power is a great idea but why spend billions on a barrage when we can use underwater turbines instead for a lot less money and enviromental impact? The only people who will win from the barrage are the company who gets the 7 year multi million building contract!! You know who you are!

[bristolbigred]

we shouldn't be wasting our time evan looking at this as it's been prooved that this type of technolgy is totaly flawed for rivers like the severn we should be putting our money in to research for technology that will genuinly benefit the environment

[garethianking]

This is a complete disaster waiting to happen! A waste of money, wildlife sanctuaries and possibly towns due to a back log of water flooding low lying areas.

[neilandfi]

Question 1: Where will you put the silt? Don't look at La Rance.. that's a silt-free river. Look at the Moncton Barrage on the Peticodiac in Nova Scotia.

Question 2: Why bother with a navigation lock? The Bristol Docks people have already stated that if they are INSIDE the barrage, they will go out of business... about 20,000 jobs will go.

[rodney89]

You can see where all the silt is, they've very kindly shown it on the computer generation on the West side of the barrage!Doh!!!!