London's key buildings 'at risk' in catastrophic flood » Local Government » 24dash.com

Parliament, Downing Street and MI5's headquarters could all be hit by floods within 30 minutes of a "catastrophic breach" of London's river defences, Westminster City Council warned today.

The council commissioned a study to map the likely course of flood waters in the capital for the "extremely small" chance that the Thames' defences failed.

Councillors said the capital was well protected by the Thames Barrier and Embankment Wall, but was likely to become more vulnerable to flooding because of rising sea levels and heavy rainstorms brought on by climate change.

According to the study, Scotland Yard and parts of Whitehall, along with thousands of homes and businesses in Westminster and Pimlico built in the flood plain, could also be at risk of flooding.

The council said the chances of floodwater inundating riverside landmarks with up to two metres of water in a matter of minutes was very small.

It would require a one in 200 year tidal flood event, the Thames Barrier failing and multiple breaches of the Embankment's defences.

Central London has not severely flooded since 1928, when floods hit the capital killing 14 people.

But councillors said they had to plan for the worst and if river defences failed, the impact could be substantial as it would be sudden and unpredictable.

Sustained heavy rain could also cause problems, as just two weeks of downpours could leave drains, underground rivers and river defences struggling to cope.

The council urged developers to help protect the capital by including natural forms of drainage in their plans to reduce the amount of water in drains and underground rivers during bad weather.

These could include "living" green roofs planted with sedum, tanks to collect rainwater, permeable paving that allows water to drain away and grassy areas.

Councillor Robert Davis said: "Like many major cities, London is built on the banks of a great river and is therefore vulnerable to climate change.

"Although Westminster is currently well protected, we must ensure the city is prepared for any eventuality by planning ahead."

He went on: "The chances of a catastrophic breach of flood defences like that in 1928 is extremely small but we always need to be prepared for the worst.

"Given climate change and the increasingly erratic weather conditions, we must plan for the future and start taking steps now to ensure London is kept safe from flooding for generations to come."

The flood risk assessment for Westminster City Council will form part of the overall plans for the borough, making sure flooding is taken into account in future developments.

An Environment Agency spokesman said London was one of the world's best protected cities against flooding from the sea.

He said: "We recently announced that the Thames Barrier, which has been closed 114 times in the past 25 years to protect London from tidal surges, will protect the city from a one-in-1,000-year flood until at least 2070.

"We are also looking at the possibility of building a bigger barrier towards the end of the century to defend the capital against rising sea levels due to climate change, as part of our plan for the Thames Estuary 2100 project.

"The Environment Agency is also working with local authorities to help them to manage the risk of flooding from overflowing surface water drains, caused when large amounts of rain fall in a short period of time."