East coast tidal Surge.

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oldgit

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Last night SWMBO and me were driving across Rochester Bridge and she noted there was rather a lot of water in the the river.
I hurrumphed and drove on,turns out she was right.
Some low lying areas on specific bits of Essex coast have been advised to go to shelters tomorrow.
Residents of Mersea have been leafleted to warn of tidal surge.
Fortunately it appears that the worst effect will be around LW.
Various gauges recorded a surge of nearly 1 metre over the normal tide heights yesterday.



The Richmond gauge appears to give peak of 1metre.


http://www.pla.co.uk/hydrographics/ltdetail.cfm?id=241


 
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Bit suprised no interest in this bit of the world.
However, suspect most of the Thames forum is in hibernation until their boating season starts around mid August. :)
 
oldgit said:
Bit suprised no interest in this bit of the world.
However, suspect most of the Thames forum is in hibernation until their boating season starts around mid August. :)
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Not sure why you are surprised. The events re tidal surge are predominantly East coast with little or no impact on nt Thames, thread you quote is on YBW East Coast Forum which is exactly where I would expect to find comment.
Your predictable pee taking of Thames folk is mildly tedious ?
 
According to Alan (an EA flood prediction guru at the Thames Barrier) they closed it twice over the weekend. On Friday night and Saturday (which was the highest astrological tide). He's well worth following on Twitter. He has posted quite an interesting graphic on closures over time. In the 2013/14 period they had to close it 50 times! I knew it was bad but didn't think it was that bad...

https://twitter.com/AlanBarrierEA
 
When the barrier was built it was estimated that it had life span of at least 50 years or so and would only be closed but a few times each year.
Think read somewhere it will be overwhelmed in less than half its design life and and that it has already been shut on far more occasions than was expected. ?
 
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If you look at the graph in his tweet you can see that through most of the years its used 2 - 4 times which I suppose is on spec. It's the massive outliners which are so shocking.

I don't want to stir up a hornets nest.... BUT <stirs the hornets nest>- it is pretty much what the climate change geeks have said would happen. More weird outliner years more often, dry as well as wet. Okay so its a very short period to look at but it is interesting.

I wonder what this year will bring. All depends on the artic blocking I suppose.
 
A very large number of the closures, especially the long clusters of closures on successive tides for several days, have been driven by extreme fluvial flows rather than surge events. In those cases the effect of not closing would have been to cause or exacerbate property flooding at this end of the river, especially above Teddington Lock

Somewhat disturbingly, EA did say a couple of years ago that the policy of closing in such circumstances was under review and we should not rely on such closures in future. In practice I think they have continued to close to avoid "relatively minor" property flooding in this area.

As for last week's event it would have been instructive to see just how the double hump of the surge, followed 2-3 hours later by the tide would have interacted as they sloshed up and down the long bathtub which is the upper tideway, had the barrier not been closed. Alan and his colleagues at the barrier may have been tempted to do the experiment so they could calibrate their model, but on balance I'm glad they didn't!
 
The closure of the barrier by the EA for extreme fluvial flows is a great idea. By closing the barrier at low tide and allowing the river to fill with flood water coming downstream, does indeed reduce the effect of upstream flooding. However, continual closing for several tides causes havoc with the downstream natural scouring that the ebb and flow of the tides causes, resulting in rapid silting down where the PLA earns its money.
 
alanch said:
The closure of the barrier by the EA for extreme fluvial flows is a great idea. By closing the barrier at low tide and allowing the river to fill with flood water coming downstream, does indeed reduce the effect of upstream flooding.
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The flood defence closures are always made during the rising tide, and they re-open as soon as the downstream level drops to match the upstream level. I think it is a misconception that the barrier allows the river to fill with water coming downstream, as the whole point of the closures is that without them, levels upstream would be higher.

Quid pro quo though, I can see that there would be less scouring with a barrier closure than without, as a certain volume which would have gone up and then come back down, doesn't.
 
Alan ashore said:
The flood defence closures are always made during the rising tide, and they re-open as soon as the downstream level drops to match the upstream level. I think it is a misconception that the barrier allows the river to fill with water coming downstream, as the whole point of the closures is that without them, levels upstream would be higher.

You are correct, that is exactly what the EA do to alleviate flooding when there is the possibility of a storm surge from the sea. But we are talking here of extreme fluvial flows, run off water coming downstream threatening flooding Richmond and above. In that case the EA can close the barrier around low water to stop the flood tide at Woolwich, leaving upstream to fill with the fluvial flow. High water is reached quicker than the upstream river filling and the barrier is re-opened after high water and the levels equalise. Closing the barrier for one or two tides for a potential storm surge does not cause much modification of the normal scouring of the tidal river. Closing it to mitigate flooding due to extreme fluvial flows over many tides in succession certainly does.
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All that free clean Energy wasted.

A second Thames Barrier may be needed sooner rather than later .
Surely this one could incorporate a water turbine or ten.
All that predictable free energy being wasted each and every day on the doorstep of probably the most profligate user of all in the UK ? Just sail past Canary Wharf during the hours of darkness.
 
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Re: All that free clean Energy wasted.

oldgit said:
A second Thames Barrier may be needed sooner rather than later .
Surely this one could incorporate a water turbine or ten.
All that predictable free energy being wasted each and every day on the doorstep of probably the most profligate user of all in the UK ? Just sail past Canary Wharf during the hours of darkness.
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Humm yep a most apt comment kind Sir

It would seem to me that real attempts to generate Power in this case Electricity, closer to where its needed, would indeed be a good thing for all the reasons available.

Lets hope that the 'powers' in this case can act in the public interest at last

NB sorry but those lights in Canary Wharf must mean that business is booming {:-)
 
Re: All that free clean Energy wasted.

Capt Popeye said:
Humm yep a most apt comment kind Sir

It would seem to me that real attempts to generate Power in this case Electricity, closer to where its needed, would indeed be a good thing for all the reasons available.

Lets hope that the 'powers' in this case can act in the public interest at last

NB sorry but those lights in Canary Wharf must mean that business is booming {:-)
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Having been in WID overnight a few times the sheer amount of light radiating from the tower and surrounding buildings does give pause for thought.
However did hear that the lights and A/C are left on for economy reasons as turning them off and on uses more energy ?
Generating the power closer to user also cuts down on the rather substantial transmission losses,perhaps also reminds users that their power has to be produced in somebodies backyard. :)
 
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