Thames Barrier

THAMES BARRIER

The Thames River Barrier was completed in 1983 and it was officially  opened by the Queen the following year. It remains the world’s second largest moveable flood barrier. The barrier has successfully prevented London from flooding for nearing thirty years and flood specialists consider it unsafe to work and live in London without its protection. It was constructed to prevent London from being flooded by exceptionally high tides, storm surges and descending fluvial flood waters. The barrier protects one hundred and twenty-five square kilometres of central London.

During its long history, London has periodically suffered from flooding and after the narrowing of the Thames in central London with the construction of the embankments in the 1860’s (see earlier blog: EMBANKMENT) the risks worsened. During the twentieth century, there was particularly bad flooding in 1928 and again in 1953 when three hundred people died across the United Kingdom. A solution clearly needed to be found and the authorities looked to the four compass points to see how flooding had been confronted elsewhere. In 1957 the river Turia flooded in Valencia, Spain, submerging the city centre in two and a half metres of water and afterwards the decision was taken to divert the entire course of the Turia out of the city centre. Such drastic action would be out of the question for London, so the authorities looked at the experiences of the Dutch, which lead for plans to build a barrier across the Thames to the east of London.

With the closure of the Pool of London as a port, the feasibility of a barrier grew in acceptance. Its chosen position was Woolwich, both for its straight river banks and because the underlying river chalk is strong enough to support weight of a barrier. The winning design was selected from forty-one proposals and work began in 1974 with the concept of rotating gates devised by Charles Draper. The barrier spans five hundred and twenty metres across the Thames and divides the river into four, sixty-one metre, and two thirty metre navigable passages.  There are four smaller non-navigable channels between nine supporting concrete piers, each formed from half a million tonnes of concrete. The actual floodgates are circular segments set in cross-section, that operate by rotating upwards by ninety degrees. They are the height of a five storey building when in position and weigh more than a naval destroyer. The gates are made of forty millimetre thick steel and they are all hollow, enabling them to be filled with water when submerged and they empty on way up.

Storm surges occasionally drive currents into the shallow waters of the North Sea which then flow south towards the Thames Estuary. Should the surges coincide with a spring high tide, the water levels become dangerous and the barrier has to be raised. The barrier is closed when forecasts indicates that water levels would exceed 4.87 metres in central London. It is designed to protect against floods of 7.2 metres above sea level. The barrier only needs raising in flood tides, on the ebb tide it is then opened to allow water to flow back out. In the 1980’s there were four closures of the barrier, thirty-five in the nineties and seventy-five closures during the first decade of the twenty-first century.

Its steadily increasing use is of concern. The designed resistance of the barrier met projections taken before considerations of climate change. New research suggests a greater level of sea level change, meaning that at current estimations the barrier will now cope only until 2070 and thereafter the barrier might not suffice. The sea surrounding the south-east coast of England has historically risen by twenty-five centimetres per century.  This has mostly been caused by the land mass sinking, an effect of post glacial rebounding, with north-west Scotland rising in accordance. In the eighteenth century the high tide was two feet lower than today.

After periods of heavy rain, floodwater travelling down the Thames also creates a significant threat. The source of the Thames is more than fifty kilometres inland and on its way to the heart of London it reaches Teddington, where it effectively begins opening into its estuary. The Thames is tidal as far as the lock at Teddington, the town’s name derives from ‘Tide End Town’. Approximately a third of barrier closures up to 2010 have been to alleviate fluvial flooding.

The threat from flooding is clearly taken very seriously by London’s authorities. Whether needed or not, the barrier is raised monthly for tests. Few people know that every Tuesday morning at ten the flood sirens in south London are tested and have been ever since the 1953 floods. In 1997 a dredger collided with the barrier preventing it from being closed for several days, as the dredger’s contents of shingle was deposited on the submerged floodgates. Fortunately the barrier wasn’t required, as the results may have been catastrophic. In the years ahead, London may well be threatened by a further source of flooding, as there are  estimations that London’s water table will have risen so much by 2030 that we will be swamped from beneath. In the nineteenth and early twentieth centuries, industry kept the water table low by extraction, but since industry has almost entirely moved away from central London the water table has significantly risen and is in places now only ten feet beneath the foundation of some buildings.

The Thames  Barrier can be reached by road, but many prefer to see it by boat and many daily tourists trips travel as far downstream as the barrier. It is worth a visit to the barrier to gain a sense of the scale of its size alone, but also because architecturally it is a structure very much ahead of its time. Designed by Rendel, Palmer and Tritton in the late 1960’s and modified in the early 1970’s, it could easily have been a boxy, concrete eyesore typical of the era.  However, its curves and reflective surfaces are suggestive of Frank Gehry’s 1997 Guggenheim Museum in Bilbao and many twenty-first century projects by the likes of Calatrava or Libeskind. The Thames Barrier Visitors Centre has inexpensive admission and it is located at 1 Unity Way, Woolwich, London SE18 5NJ

Where to view Thames Barrier and video clips of London

London in Motion has some of the best London Stock Footage and London Library Footage with moving clips of many of the above mentioned places to see, are available to browse through by simply visiting the ‘Thames Barrier’ category of this website.  New additions of London video clips are being frequently uploaded and further categories will be appearing over the coming months.