Teddington Weir Question

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GAJ52

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I know absolutely nothing about river flow management, so please forgive me if this question sounds stupid.

As a layman, I do not understand why the Thames doesn't 'drain' quicker via Teddington Weir. When there are very high water levels on the Thames (as at the moment) are the weir gates fully open or is it still controlled so London isn't flooded in the tidal Thames, also does the flow of water through the weir change at low tides i.e does it increase.

Edit : the reason I have asked this question is the flow today provided in the Thames Conditions thread seems to have decreased, but the level here in Old Windsor is the highest since the floods on 11th Jan so why would the flow decrease ?
 
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If you look at the gauges for (e.g.) Kingston, Molesey, Thames Ditton you'll see that levels in that area have decreased, consistent with reducing flow at Teddington, while as you say, the level at Old Windsor has increased.

I suggest there are at least two mechanisms contributing here:
1) Any particular "heavy rainfall event" affects different parts of the Thames catchment differently, and hence some tributaries may contribute a lot of water while others don't. Just now the the Mole, Ember, Chertsey Bourne, etc which enter the Thames below you, but above us, may not be driving very hard so to speak.
2) Generally a heavy rainfall event upstream causes a "hump" in the river which migrates downstream. Teddington may be seeing the back of the last hump while you are seeing the front of the next.

Doubtless Howard will respond regarding the specific of Weir management.
 
The complication at Teddington compared to weirs further up river is the tide. In current conditions, when the tide rises, the water backs up over the weir, slowing the flow above and causing temporary flooding at Trowlock Island. Tides are now heading towards neaps reducing this problem.
 
blenkinsop said:
The complication at Teddington compared to weirs further up river is the tide. In current conditions, when the tide rises, the water backs up over the weir, slowing the flow above and causing temporary flooding at Trowlock Island. Tides are now heading towards neaps reducing this problem.
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Altho’ I am a layman on water management I commented in another post about use of the Thames Barrier. I understand that it has been deployed for 13 consecutive tides in January this year. Altho’ it was designed to protect London from the sea surges - particularly high spring tides it is also used to allow the non tidal Thames to drain without the incoming tidal resistance. Since we had more than 3 times the rainfall of the equivalent period in 2003 even with better management of the Jubilee River it appears to me that things would have been a lot worse without the use of the Barrier. The problem is that there is reluctance to use the Barrier more often since the limit I believe is for a maximum of 50 times in any one year.. The concern with too frequent operation is that this might lead to failures. Presumably, the more often the system is used the more maintenance is necessary. The building in the flood plains – e.g. the whole of Maidenhead led to the construction of the Jubilee River which has caused more problems lower down. As other posters have commented – perhaps they will now think about proceeding with the shelved alleviation schemes that were originally projected.

Please note this is only my personal viewpoint
 
534l4rk said:
Altho’ I am a layman on water management I commented in another post about use of the Thames Barrier. I understand that it has been deployed for 13 consecutive tides in January this year. Altho’ it was designed to protect London from the sea surges - particularly high spring tides it is also used to allow the non tidal Thames to drain without the incoming tidal resistance. Since we had more than 3 times the rainfall of the equivalent period in 2003 even with better management of the Jubilee River it appears to me that things would have been a lot worse without the use of the Barrier. The problem is that there is reluctance to use the Barrier more often since the limit I believe is for a maximum of 50 times in any one year.. The concern with too frequent operation is that this might lead to failures. Presumably, the more often the system is used the more maintenance is necessary. The building in the flood plains – e.g. the whole of Maidenhead led to the construction of the Jubilee River which has caused more problems lower down. As other posters have commented – perhaps they will now think about proceeding with the shelved alleviation schemes that were originally projected.

Please note this is only my personal viewpoint
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That's interesting I didn't realise there was a limit to how many times the Thames Barrier could be used, but that does make a lot of sense as a mechanical failure could be catastrophic for London. I remember reading in the paper in Dec 2012 how the Thames Barrier was used in reverse, and closed at low tide to give more time for the non tidal Thames to drain, as you mentioned in your reply. Does anyone know if it has been used again for this purpose during these current floods ?

I have just looked at the level down steam of Old Windsor lock and its currently 4.58, at 4.94 it started coming in the garden and at 5.19 we had between 18in to 2 feet of water in the garden when the banks were breached. Worryingly there is a lot more water to come down the river and more heavy rain due on Saturday. I have just been down to the boat at Penton Hook and spoken to one of the guys in a workshop there and they are clearing everything off floor level preparing for a second flood within a few weeks - think I'll do the same !!
 
Barrier closures this season have I believe pretty much ALL been triggered by the high fluvial flow, but this isn't the barrier being "used in reverse".

The EA model the expected river levels throughout the tidal cycle, and I believe their aim is to close the barrier just early enough during the flood tide (never at low water, and usually closer to high water than to low water) to avoid serious flooding, whether that be flooding in central London as could be the case with an intrinsically dangerous tidal surge even if fluvial flows were a trickle, or as recently, flooding to the "transitional" reaches above Teddington (such as Trowlock Island and Thames Ditton island), which would otherwise be caused by a combination of high flows with tides that are high, but not necessarily exceptional.


There's a wealth of fascinating background info on John Eade's site at http://thames.me.uk/s00030tides.htm
 
I think the problem with closing the Thames barrier too often is not one of more use more maintenance, but more to do with what happens to the river downstream of the Barrier when frequent closures occur. The Thames is basically self scouring. By impeding the natural flow of the tide, both flood and ebb, silt is not moved on and the river depths decrease. There are still significant large ship movements below the Pool of London. Here lies a conflict with the EA under pressure to close the Barrier for flood control purposes, and the PLA wanting to keep it open for scouring and shipping. The odd closure over a couple of tides doesn't appear to matter much, but a long succession of closures does. I am not an expert in this field, but I know a man who is. For more info speak to PLA Hydrographic dept.
 
Since this thread has drifted slightly into the broader topic of the interaction between fluvial flows, levels, tides, the barrier, reasons to close it or not close it, etc, the following, just issued in a flood warning for Thames Ditton is interesting:

River levels are very high in response to recent rainfall and will continue to rise over the weekend. The next high tide at Thames Ditton Island is at 21:30 pm this evening and is forecast to reach between 6.3 and 6.4 metres. Flooding of the lowest lying properties on the island is possible. The Thames Barrier will be closed for this evening's high tide. Levels are forecast to reach between 6.5 and 6.6 metres for tomorrow morning's high tide at 10:15 am and the operation of the Thames Barrier is yet to be decided.

14:19 on 07 Feb 2014

Update: 6 hours after that, EA tweeted that Barrier will close for the morning tide.
 
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A friend of mine pointed out while at Richmond recently that at low tide there there was no where near as much water he was expecting to be coming through there considering all the flooding further up river, let alone what happens at high tide. This goes back to the OP's original question which about whether Teddington Weir isn't actually fully open in order to protect things below Teddington which seems to have got caught up in fred drift. I can understand about peaks and troughs moving up and down the river, but as I assume that every weir is open and rain fall has decreased this wouldn't really come in to play so much now. Are the reaches above Teddington being sacrificed to protect below Teddington?
 
bradtarga34 said:
A friend of mine pointed out while at Richmond recently that at low tide there there was no where near as much water he was expecting to be coming through there considering all the flooding further up river, let alone what happens at high tide. This goes back to the OP's original question which about whether Teddington Weir isn't actually fully open in order to protect things below Teddington which seems to have got caught up in fred drift. I can understand about peaks and troughs moving up and down the river, but as I assume that every weir is open and rain fall has decreased this wouldn't really come in to play so much now. Are the reaches above Teddington being sacrificed to protect below Teddington?
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I can assure you of two things!

One is the weir is fully drawn and some... Tedd lock will be along to confirm!

Two current levels at Tedd, Twick and Rich at low tide are as high as a good high tide. When the tide does come in (barrier not in place) then it hits the fan....

I can see how they might see it as not flooded as there is still some way to go however it is still exceptionally high.
 
Do any of you experts know - now that all weirs are fully open, or in many cases head and tail water levels are the same anyway, do the EA have any effective control left to manage river levels in individual river sections between locks? Or is the Thames now in an uncontrolled free-flow situation that only the weather can influence?
 
LimL said:
Do any of you experts know - now that all weirs are fully open, or in many cases head and tail water levels are the same anyway, do the EA have any effective control left to manage river levels in individual river sections between locks? Or is the Thames now in an uncontrolled free-flow situation that only the weather can influence?
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I think you have answered your own question..with everything open it is only a matter of time now and hopefully a little less rain..
 
Honestly , teddington weir is fully open , there are no gates left. Anyone who says otherwise is either a) off their head or b) knows absolutely nothing about how we operate the weirs.

What a ridiculous thing to say.

Go and look at the weir , there is daylight under every gate. These conspiracy nutcases make me really angry.
 
Which gate isn't fully open ?

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LimL said:
My question was partly prompted by noticing that the Jubilee river levels are lower than normal:

Jubilee River at Taplow: Current River Level: 0.26m, falling, Below normal for this location

Indicating that some level of control must be being applied?

Data thanks to http://www.riverlevels.info/jubilee-river-taplow
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That is poppycock.
I was at the jubilee river this morning,maidenhead,it was the fullest I've ever seen it and flowing like billy'oo.
 
I just thought I would throw the question out there as I couldn't believe that everything wouldn't be open and would remain open until things get to a more sensible level. Just wanted to ask the question anyway so I could be sure when I did infirm my friend of the actual facts, so thanks for confirming what I thought, didn't want to make you angry...:(
 
bradtarga34 said:
I just thought I would throw the question out there as I couldn't believe that everything wouldn't be open and would remain open until things get to a more sensible level. Just wanted to ask the question anyway so I could be sure when I did infirm my friend of the actual facts, so thanks for confirming what I thought, didn't want to make you angry...:(
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Would confirm that Brad would not want to annoy.

P.s. Anyone want to see pics of my boat charter to the Soggy Dollar Bar in the BVIs today? ;)
 
bradtarga34 said:
I just thought I would throw the question out there as I couldn't believe that everything wouldn't be open and would remain open until things get to a more sensible level. Just wanted to ask the question anyway so I could be sure when I did infirm my friend of the actual facts, so thanks for confirming what I thought, didn't want to make you angry...:(
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I confirm that Brad would not want to annoy.

P.s. Anyone want to see pics of my boat charter to the Soggy Dollar Bar in the BVIs today? ;)
 
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