Ahhhh, this feels good. Today I did something I haven't done in a long time: I went out with my camera, in the sun, to take photos just for fun. I wasn't doing it because the stupid 365 Project was making its daily demand; nor because I was at some event where tradition demands that a few badly shot pictures of blurry revellers be taken for posterity; nor because I happened to be visiting somewhere that, theoretically, I should be taking photos of. No, today it was just me, the camera, good weather, London and science podcasts. Bliss.
So it was I decided to head down to the Thames Barrier. It's only a few miles from where I live but I had never gone down there before; I soon realised I had been remiss, there were ample opportunities for some interesting photography.
The Thames Barrier, then. Why is it there? How long has it been there? How does it work? And why does it look so weird? Some of these questions are easier to answer than others. The reason it is in that specific location is quite straightforward; the Thames, if you look at it on a map, is wrigglier than a three year old with ants in their pants but in this little section, between Silvertown in Newham and New Charlton in the borough of Greenwich, the banks are quite straight and parallel to one another; this makes it much easier to build a massive, water tight, movable barrier - the second largest in the world. Also, the underlying chalk bedrock in the area happens to be a little harder than the chalk and clay on which most of London sits and so could support the structure. As an aside, London is steadily sinking into the ground much as Venice is now, but that's a problem for another century. The other interpretation of the question Why is it there? - as in Why do we need it at all? - is also simple enough, if not a little tragic.
The Thames Barrier, then. Why is it there? How long has it been there? How does it work? And why does it look so weird? Some of these questions are easier to answer than others. The reason it is in that specific location is quite straightforward; the Thames, if you look at it on a map, is wrigglier than a three year old with ants in their pants but in this little section, between Silvertown in Newham and New Charlton in the borough of Greenwich, the banks are quite straight and parallel to one another; this makes it much easier to build a massive, water tight, movable barrier - the second largest in the world. Also, the underlying chalk bedrock in the area happens to be a little harder than the chalk and clay on which most of London sits and so could support the structure. As an aside, London is steadily sinking into the ground much as Venice is now, but that's a problem for another century. The other interpretation of the question Why is it there? - as in Why do we need it at all? - is also simple enough, if not a little tragic.
In 1953 a spring tide coincided with a severe storm over the North Sea, this led to a surge in sea level of over 5 metres. The first area to be affected was Scotland where 19 fatalities were reported, but conditions only got worse as the surge travelled south into the progressively more shallow waters of the southern North Sea. Approximately 1000km2 of eastern England were flooded with the sea encroaching as much as 2 miles inland in Lincolnshire and Norfolk. Over 1600km of coastline was flooded along with severe floods in Silvertown and Canning Town in East London; just a mile down the road from me. The result was tens of thousands being made homeless and 307 deaths. At sea, many trawlers and other boats were lost producing another 224 deaths.
Sadly, by comparison, we had it easy. The Netherlands, where a fifth of the country is below mean sea level and half of it is at less than 1m above sea level, over 1800 people were drowned as a quarter of the country was lost to the sea. There were also long term effects as being flooded by sea water is not like being flooded by fresh water. Having that much salt dumped onto the land devastates farm land or, indeed, any land where you might want vegetation to thrive.
As a result of this natural disaster, the second worst in British recorded history, the Government began planning how to protect us from such 1 in 1000 year catastrophes. Sea defences around the country were built/bolstered and a plan for some kind of barrier to protect central London was commissioned.
The design was first drawn up in the 1950s by Charles Draper but construction didn't begin until 1974; it was opened by Her Majesty The Queen on my 1st birthday in 1984 and, in today's money, it cost nearly £2b. There are five large piers and two smaller ones creating four 60m navigable spans and two 30m navigable spans. The 60m spans were specifically that size so as to be the same as Tower Bridge, i.e. anything that could get through Tower Bridge had to be able to get through the barrier too. I think my photos struggle to convey the scale of this area adequately; the river is over half a kilometre wide here, and you could fit Tower Bridge onto it four times just in the central section. It's huge.
Sadly, by comparison, we had it easy. The Netherlands, where a fifth of the country is below mean sea level and half of it is at less than 1m above sea level, over 1800 people were drowned as a quarter of the country was lost to the sea. There were also long term effects as being flooded by sea water is not like being flooded by fresh water. Having that much salt dumped onto the land devastates farm land or, indeed, any land where you might want vegetation to thrive.
As a result of this natural disaster, the second worst in British recorded history, the Government began planning how to protect us from such 1 in 1000 year catastrophes. Sea defences around the country were built/bolstered and a plan for some kind of barrier to protect central London was commissioned.
The design was first drawn up in the 1950s by Charles Draper but construction didn't begin until 1974; it was opened by Her Majesty The Queen on my 1st birthday in 1984 and, in today's money, it cost nearly £2b. There are five large piers and two smaller ones creating four 60m navigable spans and two 30m navigable spans. The 60m spans were specifically that size so as to be the same as Tower Bridge, i.e. anything that could get through Tower Bridge had to be able to get through the barrier too. I think my photos struggle to convey the scale of this area adequately; the river is over half a kilometre wide here, and you could fit Tower Bridge onto it four times just in the central section. It's huge.
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| Used with permission |
So how does the damn thing work? Hopefully the diagram to the right will help explain. Between each pier there is a hollow gate with a circular cross section; when the gates are closed this rests in a depression cut into the riverbed allowing the free flow of water. To stop the fluvial flow these can be rotated such that nothing pass. To close the barrier isn't a simple task, though, it requires coordination with many other flood defences in the region and costs about £16000 per go.
The Barrier can protect London in two different ways depending on which direction the flooding is expected: from the North Sea or from the river itself. It's easy enough to imagine how it might protect London from the type of disaster experienced in 1953, you simply close the gate and, with any luck, nothing will get passed it and the areas down stream won't be too badly damaged either. But it can also help if there has been a lot of rain and the flooding is coming from upriver in the Thames basin. It does this by closing the gates during a low tide, this means that once the tide starts rising again it can't get back up river and this creates a basin of low level water that the flood water can run into allowing it to drain out of the city more quickly.
As it approaches it's 30th birthday the Thames Barrier continues to provide protection for Londoners; disconcertingly, though, this protection is having to be deployed more and more frequently. In it's first 6 years of use it was only closed 4 times, in the last decade it has averaged 7 times per year. Is this a possible measure of global warming? Are flood events occurring more often? In the fantastically complex science of climate change it isn't possible to draw a conclusion from one measure of anything, but it would seem to support that. The barrier was only designed to protect against a surge in sea level of 4.67 metres. If sea levels raise by a metre this century, as seems likely, then the capacity of the barrier to protect the capital would be greatly reduced. Add to that the slightly odd fact that Britain is tilting (the south and east are sinking and the north and west are rising at about 5cm/century) and the future looks ever more precarious. The original design was supposed to provide solid protection up until the year 2030 followed by a period of ever diminishing returns after that. The Environment Agency, however, who now runs the barrier, has said that it has no intention of replacing it before the year 2070. I do wonder if this is based on good scientific advice or on Governments that are not willing to spend money on insurance policies. Hopefully it won't take another disaster of the kind seen in 1953 to force their hand.
The Barrier can protect London in two different ways depending on which direction the flooding is expected: from the North Sea or from the river itself. It's easy enough to imagine how it might protect London from the type of disaster experienced in 1953, you simply close the gate and, with any luck, nothing will get passed it and the areas down stream won't be too badly damaged either. But it can also help if there has been a lot of rain and the flooding is coming from upriver in the Thames basin. It does this by closing the gates during a low tide, this means that once the tide starts rising again it can't get back up river and this creates a basin of low level water that the flood water can run into allowing it to drain out of the city more quickly.
As it approaches it's 30th birthday the Thames Barrier continues to provide protection for Londoners; disconcertingly, though, this protection is having to be deployed more and more frequently. In it's first 6 years of use it was only closed 4 times, in the last decade it has averaged 7 times per year. Is this a possible measure of global warming? Are flood events occurring more often? In the fantastically complex science of climate change it isn't possible to draw a conclusion from one measure of anything, but it would seem to support that. The barrier was only designed to protect against a surge in sea level of 4.67 metres. If sea levels raise by a metre this century, as seems likely, then the capacity of the barrier to protect the capital would be greatly reduced. Add to that the slightly odd fact that Britain is tilting (the south and east are sinking and the north and west are rising at about 5cm/century) and the future looks ever more precarious. The original design was supposed to provide solid protection up until the year 2030 followed by a period of ever diminishing returns after that. The Environment Agency, however, who now runs the barrier, has said that it has no intention of replacing it before the year 2070. I do wonder if this is based on good scientific advice or on Governments that are not willing to spend money on insurance policies. Hopefully it won't take another disaster of the kind seen in 1953 to force their hand.
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| The view to the west, Docklands and the O2 can be seen in the distance |
After three hours I had only covered about 200 yards of the riverbank but I had had a great time. The weather and light were fantastic and it was good to be there knowing that I could write it up at my leisure in the style that I used to before the 365 Project consumed my hobby. I knew I would have the time to look into the history of this impressive structure and do it some justice in words as well as in pictures. Basically, I have my blog back and I love it. I hope you enjoy it too.
