The London Assembly Environment Committee is seeking assurances from the Mayor of London that the city’s sea flood defences are both robust and future-proof.

The Thames Barrier has been raised eleven times in the past few weeks, reinforcing its importance to London as protection against the tidal Thames.

The Assembly first highlighted concerns about the sustainability of the capital’s flood defences as long ago as 2002 - and again in 2005 and 2011.

Environment Committee Chair Murad Qureshi AM said that with current weather events now becoming more prevalent, it was both "wise and timely" to check the effectiveness of the Thames Barrier and look ahead to what will replace it in the future.

An extraordinary simulated map of the devastation flooding could cause in London was released by the Environment Agency in 2011.

The simulation shows the consequences of a flooded Thames. This is the area that may be affected by flooding in a 1 in 1000 year flood event, if none of the Thames defences, barriers and walls were in place. 

It does not reflect the area that would have been affected by the December storm and tidal surge.

Mr Qureshi said:

“The Environment Agency has graphically demonstrated the scenes of devastation that could be visited on London if its flood defences were overwhelmed. It requires the immediate application of the kind of long term planning that produced the Barrier, to ensure its adequate replacement”.

The Thames Barrier was designed to protect London from flooding until 2030 and beyond- however, the standard of protection it provides will gradually decline over time after 2030.

In January 2013 the Environment Agency rejected a call for a new Thames Barrier to be built as a matter of urgency by one of the engineers that built the Thames Barrier in the 1980s.

Richard Bloore wrote a letter to the the Times newspaper saying that the flooding in New York should serve as a warning to London. In response the Environment Agency said at the time it had no plans to replace the Barrier before 2070.

In 2012 the Environment Agency said that early indications were that subject to modification, the Barrier would be capable of providing continued protection to London against rising sea levels until at least 2070.  The Agency said:

“However, economic assessment and analysis into the risk of Thames Barrier failure suggests it may prove safer and more cost beneficial to construct a new barrier further downstream at Long Reach before the end of the century (to become operational ~2070). Upgrading the current system of associated tidal defences will be required from around 2035.”

Opened in 1982 and operated by the Environment Agency, the Thames Barrier, the world’s second largest movable flood barrier, was designed to withstand a 1 in 1000 year flood event.

The final cost came to over £535 million (valued at £1.4 billion at 2007 prices). There was no private funding, and the cost was met through central government funding (75 per cent), with the remainder provided by local government.