The River Thames meets the North Sea forming the Thames Estuary, a strongly tidal estuary that crosses the heart of London. To protect the city from flooding caused by tidal surges, the Thames Barrier was completed in 1982. But as sea levels rise in a warming world, the Thames Barrier may no longer be enough to protect London, reports The Guardian.
London's main defence against flooding, the Thames Barrier consists of 10 gates that span 520 metres across the River Thames which close to create a wall of steel preventing water flowing upstream towards the capital. Barrier closure is triggered by a combination of high tides forecast in the North Sea and high river flows; heavy rainfall events can increase the tidal flood risk in the estuary. The network of tidal flood defences includes the Thames Barrier and other major barriers and gates, as well as 330 kilometres of walls and embankments, and over 400 other structures such as flood gates, outfalls and pumps.
The Environment Agency has recognized the need to take an adaptive approach as sea levels rise, and recently updated the Thames Estuary 2100 Plan, a long term strategy to manage the risk of flooding in London and throughout the estuary. First published in 2012 and subject to regular review, the plan was the first adaptive flood risk management strategy of its kind. The aims of the plan are to take an adaptive approach to manage flooding and create climate resilient communities, while delivering social, cultural and commercial benefits, as well as an environmental and biodiversity net gain.
While the recent update says the Thames Barrier continues to be effective as part of the broad flood defence system, it also recognises some key milestones for action will have to be brought forward because of accelerating sea level rise. Specifically, the defences upstream of the Thames Barrier in inner London will need to be raised by 2050, 15 years earlier than in the original Plan.
The options to adapt to sea level rise by the end of the century include upgrading the Thames Barrier, creating flood storage areas at several marshes, and building new barriers, but the decision on them will not be made until 2040. Critics say that timescale is too slow: the Thames barrier is ageing and is expected to age faster if it is closed more often, something that has been happening since it was built, in part to alleviate fluvial flooding during excess rainfall, even though the barrier’s main function is to stop tidal floods.
The costs of upgrading flood defences in the Thames Estuary until 2100 are expected to amount to £16.2 billion, a 50% increase since the 2012 estimate, due to defences deteriorating faster than expected. The Environment Agency plans to work with those who benefit from flood defences – businesses, landowners, infrastructure providers and others – to explore opportunities to obtain investment contributions from them; an investment strategy is expected by 2025.
