UK: Protecting London from current and future flood risks

By Sebastian Catovsky, Head of the Adaptation Sub-Committee

The Thames Barrier is one of the country’s most high-profile symbols of adaptation. It was fitting, therefore, that the Committee on Climate Change adaptation team recently visited the Thames Barrier for its monthly test closure.

Protecting London from sea level rise

There are over £200 billion of capital assets in the Thames tidal floodplain, including 500,000 properties, nearly 100 tube/train stations, City airport, 400 schools, 16 hospitals and 8 power stations. 1.25 million people live or work below the Thames average high tide. The Thames Barrier means that the flood defences in central London are three metres lower than they would have been without the barrier in operation.

Indicator of a changing climate

The Thames Barrier has been closing with increasing frequency since it was built. It was closed 34 times in the 1990s to protect London from flooding and 80 times in the 2000s. Rather than just closing to protect London from a tidal surge up the Thames, the Barrier has been increasingly closing to keep high freshwater flows from combining with a high tide.

Long-term resilience

When the Thames Barrier was designed, there was no knowledge of climate change and its impacts on sea level rise. The design engineers at the time were however aware that the South East was slowly sinking – the result of a natural geological phenomenon. They had the foresight to build an 8mm per year sea level rise allowance into the design of the barrier. This means that the Thames Barrier’s current standard of protection (0.1% chance of overtopping in a given year or once in 1000 years) will last until 2030.

Decision-making under uncertainty

The Environment Agency project “Thames Estuary 2100” looking at options for protecting London after 2030 has pioneered an approach that shows how you can take long-term decisions to adapt flexibly to climate change in the face of uncertainty.

Thames Barrier closing

This month’s test closure was a bit different, because it was timed to coincide with a simulated East Coast storm surge, as part of Exercise Watermark, the Government’s test-run of its emergency procedures to respond to a severe flood event. The exercise was set up in response to the Pitt Review after the major floods in Summer 2007, which damaged 55,000 homes, led to the death of 13 people, and cost the economy £3.2 billion (2007 prices).

As the Adaptation Sub-Committee’s first report highlighted, emergency planning is a priority for early adaptation action. It will make the UK more resilient to today’s climate and increase the UK’s preparedness in the future. The benefits from better emergency planning for extreme weather will remain regardless of the amount of climate change in the future, and therefore the measure is known as a “low-regrets” adaptation option.

In its second report due this summer, the Adaptation Sub-Committee will develop some of the themes highlighted by the Thames Barrier visit. In particular the Sub-Committee will set out some indicators to measure how the UK’s vulnerability to climate is changing and how climate risks are being incorporated into decisions in priority areas for early adaptation action.