Friday, 10 January 2014

Thames Barrier


Does closing the Thames barrier, cause flooding further upstream, on the non-tidal reaches?

My reasoning is that if the river cannot get down to the sea, the flood water has to go somewhere. Which logically, points me to the conclusion that "yes, it does". However, Peter (the marina manager) finds that notion highly laughable. And of the people who wrote into the Oxfordshire newspapers to complain about it recently, he said "They are as deluded as you are".

Who's right?
(google was inconclusive)

"Oh, wouldn't it be nice..."

11 comments:

  1. I was always under the impression that the Thames barrier was to protect against tidal flooding - so when it is closed it is only for a relatively small period of time - and the amount of time it is closed wouldn't give the water coming downstream enough time to build up and cause further flooding upstream. The barrier is only closed when there is a chance that such a high tide would actually cause the flood plains to do what they should be doing - absorbing the tidal surge and flooding - most of the flood plains have been built on.

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  3. Hi Graham. Whenever the thames barrier goes up, the water here increases in depth. I suspect, it's water being held back at weirs rather than the barrier
    itself. But I have observed that there is a direct correlation between the two events.

    Last night, they opened up all the weirs, and the flow increased dramatically (bobbing us about alarmingly). This morning, the river had dropped three inches
    or more.

    Why didn't they do that days ago? I think it was to stop london flooding. Therefore, raising the barrier *does* have an effect on the upper reaches.

    I took a small straw poll of residents yesterday. Results ranged from "of course it does!", to "it does seem to build up more". Nobody said "don't be so stupid".



    *shrugs*

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  4. Hmm, with the weirs closed up then there will be the chance of flooding in the areas before the weirs - as the water will back up.

    They're probably doing this to prevent the flow heading down towards London when the Thames barrier is closed.

    So it's the control of the weirs rather than the Barrier itself that is causing the rising of the river in your area, and the upper reaches but there is a correlation.

    We currently live close to the River Arun, and there is no barrier to stop tidal surges - it's been pretty amazing seeing how it floods during high tide, the excess rain.

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  5. Hi Ken

    I would find it amazing if the Thames lock keepers were closing weirs and flooding their pounds simply to protect London. If that's what they ARE doing, I wonder how they time their weir's closure to co-incide with the Barrier being raised when:

    a) the Barrier is only closed for a couple of hours at high tide,

    and

    b) you take into account how long it would take water from different locks to reach the London pound above the Barrier. I suppose the EA might have computer models to predict this...

    Anyhow, the good news is that the river levels in Abingdon have dropped, so you should start to see some improvements with you in the next few days.

    Stay safe
    Alistair

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  6. Hi Alistair and Graham. thanks for your comments. Peter's going to ask the weir keepers what transpired in a post match analysis.


    Based on the aggrevaton and eyebrow raising of local people (with more river knowledge than myself), I'd assumed the barrier lifting was more of an all day
    event, rather than a two hour slot. On the days it happens, a large amount of water seems to come out horizontally, and the flow increases at night. But I'm
    open to the possibility that I've made 5 out of 2+2. Maybe the weirs *were* left fully open with no adjustment of levels at all.

    >>I would find it amazing if the Thames lock keepers were closing weirs and flooding their pounds simply to protect London.

    Why would that be amazing? With such a dense population there, I presume it would be protected at all costs.

    >>Anyhow, the good news is that the river levels in Abingdon have dropped, so you should start to see some improvements with you in the next few days.

    good news. it's started receding here now too.


    Cheers...

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  7. Hi Ken. Not heard from you recently. Hope all is well with you.

    Cheers, Alistair

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  8. Hi Alistair. Had to deploy the waders again, but otherwise we are fine. The river went down a couple of inches, but then came straight back up. Had a couple of weeks away from the blog, because it's been my birthday, and I didn't want to moan about our own circumstances, when other people are dealing with things that are so much worse.. Thanks for the concern, though. Cheers...

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  9. With all the flooding upstream now and with more rain predicted what effect will it have if the barrier is closed due to high tides on Thursday/Friday?

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  10. maybe this will help: http://www.bbc.co.uk/news/magazine-26133660

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  11. Thanks for that, Ian.

    Hi mickf. Have to put my hands up and say "I don't know". Haven't a clue what they are doing. Sheena seemed to think it was closed all day yesterday. It dropped a couple of inches here today.

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