The Thames river barrier was built between 1974 and 1984 to protect London from floods caused by high tides and storm surges. Built 523 metres wide across the stretch of the river, the gate is 10.5 metres high and weighs 3500 tonnes. Sounds pretty safe doesn't it? Prior to 1990, the barrier closed on average just twice a year. On average since then it has closed 4 times a year, with a peak of 14 in 2003. Surely now the time has come to build up the barrier again before nature catches up with us. In this I'll talk about issues which could potentially lead to inreased chances of flooding in London over the next century.

The probable effects of climate change will increase the likelihood of flooding in the Thames Gateway. The future increase in global temperatures as predicted by IPCC, to a minimum of 16 degrees (global average, increasing from 2008s 15.5), or the maximum of 19 degrees, will cause a rise in sea level as well as changes to UK weather conditions.

By 2050, London will have 20% more rain than at present, and by 2080- 30% more. Most of this is likely to occur in heavy bursts. Such an increase in the levels of winter rainfall will increase peak river flows and in turn shorten the lag time, causing rivers such as the Thames to reach bank-full discharge point and ultimately flood the surrounding land. The area surrounding the Thames River will only lead to increase this problem because most of it is urbanised. As a result water would reach the river very quickly as surface run off over concrete and brick and would not be intercepted by vegetation, or infiltrated by soil. This would shorten the lag time and increase the likelihood of the Thames breaching bank-full discharge point- causing it to flood. Figures suggest that '150mm of rain in 24 hours on London could cause devastating flash flooding'. Would this breach the current barrier?

During the 21st century this problem of shortened lag time due to surface run off will only increase if proposed developments on the Thames gateway region are carried out. The shortage of affordable homes looks set to lead to developments on the Thames Gateway area i.e. more concrete, more buildings, less vegetation and less exposed soil. When this is carried out flooding risks will only increase further, as more water will reach the river faster (shortened lag time), thus increasing the chances of the bank-full discharge point being breached. Surface Run off will again increase, but both water interception by plants, and water infiltration by soil will also fall. Potentially with so many large scale developments being carried out alongside the river, the channel itself could become narrower. Ultimately this would again only increase the chances of flooding.

Changing weather conditions such as increased gales (40% across UK) caused by areas of low pressure could also increase the chances of London flooding, because they in turn increase the likelihood of a heavy storm surge hitting London. Huge elevations in sea level caused by low pressure could veer into the North Sea and with north easterly winds blowing against it, the surge could be moved towards the south east and 'funnelled' into the Thames Estuary. This was the case with the New Orleans floods of 2005. With increases in gales, the chances of north easterly winds occurring are only greater. If a surge did occur, the existing Thames barrier could be overwhelmed at any time.

Changes in sea level caused by global warming will also increase the likelihood of the Thames flooding. A Eustatic rise will occur when the ice masses at the North and South poles melt. This could cause the sea levels in the Thames gateway region to increase by '90cm by 2080', increasing likelihood of London flooding as the Thames barrage could be breached.

Isostatic changes in sea levels are also set to occur, increasing the chances of the Thames flooding. The UK is gradually tilting as it recovers from the weight of ice sheets which sat over the north and northwest of the country during the Ice Age. The northwest is rising, but the southeast is sinking causing an apparent change in sea level (isostatic recovery). This effect would leave the Thames even more vulnerable to flooding as sea walls and barriers would be more likely to be breached. The current projections are that the existing barrier will last the combined effects of isosatic and eustatic sea level rise until 2030.

So what to do? How to tackle the situation? Do we combat the issue of global warming itself or simply protect ourselves against its probable effects? Should London be put ahead of all the other places in the UK for flood protection, even if they are at a higher risk (i.e. Boston)?

(In case it seems weird for me to be sounding all scientific after reviewing pot noodles, just to let you know I study Geography and Biology).