The Thames Barrier is a movable barrier system that is designed to prevent the floodplain of most of Greater London from being flooded by exceptionally high tides and storm surges moving up from the North Sea. It has been operational since 1982. When needed, it is closed (raised) during high tide; at low tide, it can be opened to restore the river’s flow towards the sea. Built approximately 3 km (1.9 mi) due east of the Isle of Dogs, its northern bank is in Silvertown in the London Borough of Newham and its southern bank is in the New Charlton area of the Royal Borough of Greenwich.
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Background
Flooding in London has been a problem since the city was first established in Roman times.[1] In 1954 the Waverley Committee, established to investigate the serious North Sea flood of 1953 which affected parts of the Thames Estuary and parts of London, recommended that “as an alternative to raising the banks, the possibility and cost of erecting a structure across the Thames which could be closed in a surge should be urgently investigated”.[2] A large number of designs were put forward, ranging from a huge road viaduct with two 500 foot (150 m) sluice gates crossing the Thames at Crayfordness to flap gates lying on the river bed and floated up by compressed air.[3] By 1965, when the Greater London Council (GLC) took over responsibility, two major schemes were under consideration, costed at £24 million and £41 million respectively[3] (£500 million and £800 million at 2020 prices).
In 1966 Sir Hermann Bondi was asked to take an independent view of the situation. He considered the estimated construction costs and the probability of a flood and of damage if the barrier was not built. He strongly recommended that a barrier should be built in order to avoid the catastrophe of flooding central London, and a site was agreed at Woolwich.[3]
The barrier protects central London against a storm surge, caused when a deep depression forms to the north of Scotland and progresses across the North Sea and south-easterly towards southern Scandinavia. When such a surge coincides with a high spring tide, the high winds associated with the depression can funnel the water up the Thames Estuary and cause surges of up to 3.5 metres. The planners assessed that in the absence of a barrier, such a surge could inundate 45 square miles (117 km2) of land, put hospitals, powers stations and the London Underground out of action and cause damage estimated in 1966 at £2.0 billion[4] (about £50 billion at 2020 prices). The barrier was designed to provide a flood defence capable of resisting a once in 1000 year surge tide at a base date of 2030.
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