| Environmental factors are making London more liable to flooding – but factors within our control are threatening to make the dangers worse than ever... |
The rising tide that threatens Britain's capital city
WORKERS, DEC 2005 ISSUE
London has always been at risk of flooding. In 1236 John Stow reported that "The Thames overflowed and in the great Palace of Westminster men did row with wherries in the midst of the hall." Samuel Pepys wrote in his diary on 7 December 1663, "There was last night the greatest tide that was ever was remembered in England to have been in this River all Whitehall having been drowned."
The last time central London flooded was in 1928, when 14 people drowned. In 1953 there was disastrous flooding on the East Coast and the Thames estuary with a toll of over 300 lives. Fortunately, this flood did not reach central London's highly populated low-lying areas.
The city is now protected by a combination of barriers, embankments and levees. The Thames Barrier gives a high standard of defence to the 420,000 London properties at risk from Thames tidal flooding. Beyond 2030, the Barrier and its associated defences will need to be upgraded, at a currently estimated cost of £4 billion, most of which the government should pay.
But tide levels are rising in the Thames estuary, relative to the land, by about 60 centimetres per century, due to higher mean sea levels, greater storminess, bigger tide waves, the tilting of the British Isles (with the south eastern corner tipping downwards) and the settlement of London on its bed of clay.
The area at risk in the Thames estuary is home to 1.25 million people. Flooding could cost £12 billion. We need a comprehensive flood risk assessment for London, identifying the equipment, training, information and contingency planning requirements of the capital. We also need a full map of London's drainage system, more detailed maps of flood risk areas and better knowledge of the state of our watercourses and drains.
The emergency services responded superbly to London's floods in autumn 2000. But the Fire Brigade has no statutory duty to respond to floods, which limits its ability to acquire necessary equipment and other resources.
London's River Thames: floods could endanger the homes of 1.25 million people
Drains
The Environment Agency, with the duty to supervise and warn on flood risk, has no responsibility for the drainage system, despite the serious risk of flooding from this source.
London's underground drainage system was constructed by the Victorians in the 1850s and has suffered a chronic lack of investment ever since. The sewers are designed to carry both sewage and rainfall. They are under more pressure than ever now that two-thirds of London's front gardens are paved over, the equivalent of 22 Hyde Parks or 5,200 football pitches.
The more ground covered by impermeable hard surfaces such as concrete or paving slabs, the less rainfall will soak into the ground and the more will run into underground drains. At times of heavy rainfall, the drainage pipes overflow. The flash floods of August 2004 in west London damaged homes and streets: a million tonnes of raw sewage overflowed into the Thames. Thames Water has recommended the construction of a new 35-kilometre storage and attenuation tunnel, which would cost £1.5 billion.
Defences
The Greater London Autority recommends improving river flood defences along the Thames in Hammersmith, Chiswick and Twickenham, and along many tributary rivers such as the River Lee. For most of the 2,400 defences, the landowner is responsible for paying for and carrying out maintenance work. Yet it is often impossible to identify who owns the land. Some 5% of East London's tidal defences, 11 of the 223 kilometres, are in poor or very poor condition. Outside London, towards the coast, the condition of 65% of defences is not even known.
The Environment Agency says that the top priority for planning against flood risk is to avoid building in flood risk areas. Yet London's Mayor Ken Livingstone and the GLA are aiming to have at least 120,000 new homes built and up to 250,000 new jobs created in the Thames Gateway area of east London by 2016; 45% of these houses and 85% of these new jobs are expected to be sited within the flood plain.
But new homes and workplaces should not be built only to become devastated by flooding. The chair of the GLA's Environment Committee has said of the Mayor's plans, "We're extremely concerned about development plans for East London, and the building of thousands of new homes in Thames Gateway. These plans are simply not taking the flood risk seriously enough." The Environment Agency, the Thames Gateway London Partnership and the Association of British Insurers agree.
Risk
London is not alone. Approximately 10% of the population of England live within areas at risk from flooding, containing property worth over £220 billion. The plight of New Orleans has prompted the Dutch government to review anti-flood measures in regions below sea level to ensure they would be adequate in an emergency. It upgraded its ancient system of dikes and dunes after a powerful storm breached sea dikes in the south of the Netherlands in 1953, killing more than 1,800 people. Today, the Netherlands has some of the world's best defences against flooding, including a chain of 12-metre-tall steel walls suspended by piers in the open sea. Also vulnerable, Venice is installing a similar system.
