"Thames Barrier": How the British Defend London Against Massive Flooding

London, like New Orleans, is located on a major river, called the Thames, which, like the Mississippi River, intermittently floods from heavy rainfall, surge tides or both. Surge tides for the Thames originate in the North Atlantic and generally pass to the north of the British Isles. Occasionally, however, northerly winds force them down into the North Sea, sending millions of tons of extra water up the Thames River, placing an estimated 7.5 million Londoners and between 12 and 14 million residents living in the London metropolitan area, as well as their personal property and England’s critical infrastructure, at risk for harm (census estimate 2005). (1)

As a result of this risk, the government authorized the design and build-out between 1974 and 1982 of a massive flood control structure called the “Thames Barrier”. This structure stretches across a 1,500 foot stretch of the river at Woolrich Reach. It is the world’s second largest movable flood barrier after the Oosterscheldekering in the Netherlands.

2,000-Year History of Thames Flooding

The Thames is the earliest British river mentioned in Roman history. It rises at Thames Head in Gloucestershire and winds 220 miles on its course due east to the North Sea. Oxfordshire, Buckinghamshire, Greater London and Essex line its left bank and Wiltshire, Berkshire, Surrey, Greater London and Kent are on its right bank. Teddington Lock is the highest point on the River Thames to which tides penetrate; it is located in the western suburbs of London and experiences tidal ebbing and flowing four times every twenty-four hours. Further west of Teddington Lock, the Thames carries fresh water. At Teddington Lock, the fresh water joins tidal waters rushing up from the North Sea.  

One of the most famous Thames floods in recent memory occurred on the night straddling January 31 and February 1, 1953. A vicious storm arose from “the combination of a north westerly gale, a very deep area of low pressure, a high spring tide and the topography of the North Sea (which gets narrower and shallower in the south).” (2) The waters piled up at the southern end of the North Sea near the Thames Estuary, which is confluent with the Thames River. The storm was one of the most devastating natural disasters ever recorded in England and struck the Netherlands across the English Channel even harder.

The sea level rose nearly nine feet above normal high spring tide levels causing exceptional flooding along the East Coast of England and rushing up the Thames Estuary, killing 307 people and 46,000 head of livestock, and damaging or destroying 24,000 homes. The storm surge submerged the whole of Canvey Island in the Thames Estuary, killing 58 people and necessitating the evacuation of its 11,000 residents. (2)

The 1953 River Thames flood was preceded during the previous 2000 years by numerous deadly floods. The earliest recorded flood on the River Thames was in AD 9. Some 29 years later another flood occurred that reportedly drowned 10,000 people. In 1774 another great flood on the Thames washed away Henley Bridge. Other floods occurred in 1848, 1852 and 1875.

One of the worst floods on the non-tidal Thames (west of Teddington Lock) in recent history occurred in 1894 and was due to exceptionally heavy rainfall; approximately eight inches of rain fell in the 26 days prior to the flooding peak. The 1894 flood levels are recorded on plaques at many of the locks along the Thames. Another more recent flood caused by snow, storms and rain occurred in March 1947. The River Thames below Chertsey was three miles wide, isolating the towns of Wraysbury, Datchet and Runnymede. In Reading a thousand people had to leave their homes and in Maidenhead the floods were over six feet deep.

Building the Thames Barrier

The 1953 Thames flooding prompted the government to appoint a committee to look at the flood problem. One of the recommendations made by the committee was to erect a storm surge barrier across the Thames. The main problem with building the barrier at that time was the surge in shipping volume using the London docks. The ships were also getting bigger. This meant that any constructed barrier would require an opening of around 1,400 feet. The committee received a number of proposals finally accepting a design by Charles Draper for a 1,700-foot wide barrier crossing the Thames at the Royal Docks, about 9 miles from London Bridge. The three huge docks comprising the Royal Docks, easily visible in any aerial view of the Thames Barrier, were built between 1880 and 1921 in marshes to provide berths for large vessels that could not be accommodated further upriver, closer to London. The cost of building the Thames Barrier exceeded a billion pounds.

The Thames Barrier consists of 10 gates: four 200-feet wide; four 103-feet wide and two small ones, supported by 9 piers. All the gates are made of steel. When raised, each of the four main gates is as high as a five-story building. Gates can be raised in high or low tide and when in the open position rest level with the river bed, so navigation is not impeded. Charles Draper designed the concept of rotating gates. The Woolrich site was selected because of the relative straightness of the banks, and because the underlying river rock was strong enough to support the massive barrier. Engineering information about constructing the barrier is available at: http://www.mech.uwa.edu.au/~kamy/Thames%20Barrier.htm; accessed January 5, 2006.
The Thames Barrier has been used (raised from the floor of the river) over 90 times since 1982. In addition it is raised every month for testing. The Thames Barrier is currently operated by the Environment Agency. The Thames Barrier was specifically designed to handle rising sea levels until between 2030 and 2050.

Rising Sea Levels Indicate Need for New Flood Structure

To the surprise of some, on January 9, 2005, the Sunday Time Britain (http://www.timesonline.co.uk/article/0,,2087-1431511,00.html; accessed January 5, 2006) ran an article by science editor Jonathan Leake that Britain would soon need to build a dyke (British variant of “dike”) stretching from Essex to Kent across the Thames Estuary to protect Greater London from rising sea levels. The dyke would stretch up to 10 miles across the Thames Estuary from Sheerness, in north Kent, to Southend in Essex, making it one of the biggest engineering projects ever undertaken by Britain. Specifically, the giant dyke would be built between Shoeburyness, east of Southend, and Sheerness on the Isle of Sheppey.

Researchers found that the current rise in greenhouse gas emissions are causing sea levels to rise far faster than the two to three feet expected by 2100 when the Thames Barrier was built. In addition, London is sinking at a rate of about 8 inches each century. Leake writes that the researchers “warned that London, without extra sea defences [sic], faces inundation…A key finding was that if the city’s existing defences were to be breached, then Westminster and other parts of central London could be 6 feet deep in water within an hour. The report [also] said: ‘Such rises pose a serious threat to human life particularly when considering the high population density of the Thames estuary. The risk of inundation of many central London hospitals adds further to this strain.’  

The Dutch have already built a similar long dyke to reclaim land from the sea. Britain’s new dyke would contain numerous gates to allow water to flow in and out of the Thames Estuary according to the tides, but, writes Leake, “engineers would also be able to shut the gates if a flood seemed likely. The barrier might also include a road and hydroelectric power generators.”

In summary, Britain continues to proactively manage the risk of future Thames flooding, and the damage to life and property it will cause, by investing in very expensive and very large public works designed to minimize the probability of the inundation of its capital city, London.  

Sources:

1. “The Thames Barrier” at: http://wwp.greenwichengland.com/tourism/barrier.htm; accessed January 5, 2006.

2. “The River Thames: The Effect of Weather and Tides” at: http://www.the-river-thames.co.uk/weather.htm; accessed January 4, 2006.