London is facing flash flooding again, disrupting lives and livelihoods across the capital, and demonstrating yet again that we are still vulnerable and exposed to more frequent and intense rainfall due to climate change.
London has so far escaped the worst of the current weather, with parts of Bedfordshire, for instance, experiencing in a few hours the equivalent of the average rainfall for the whole of September.
But Londoners can see for themselves that their city, like the rest of the UK, is struggling to cope with the impacts of climate change.
A warmer atmosphere can hold more moisture, so rainfall is increasing across the UK. According to the State of the UK Climate 2023, published in July by the Met Office, five of the 10 wettest years for the UK since records began in 1836, and all of the warmest years since 1884, have occurred in the 21st century.
Winters in particular are bringing more rainfall, with the most recent decade 24 per cent wetter on average than during the baseline period between 1961 and 1990. Bouts of heavy rain are also becoming more frequent.
Met Office data show that last year was the seventh wettest for south-east and central south England, and this summer was the sixth wettest on record.
And things will only get worse. Global warming, and impacts such as heavier rainfall, will continue to increase until the world stops adding carbon dioxide and other greenhouse gases to the atmosphere, and reaches net zero emissions.
Many countries are seeking to reach net zero emissions by 2050. But that means rainfall will become even heavier and more common for at least the next 25 years.
London is particularly vulnerable to heavy rainfall because it is a large urban area covered by impermeable man-made surfaces. Our drainage system is still largely based on the original Victorian network, which was not built to cope with the volumes of rainwater we now suffer.
In July 2021, the capital was inundated by heavy rainfall which flooded more than 2000 buildings and crippled parts of the road and Tube network. It exposed deficiencies in London’s preparedness flash flooding. The authorities did not have, for instance, a list of basement properties where people were at risk of drowning. Fortunately, nobody died, but the damage and disruption from the flooding had a significant economic and financial cost.
The risks of flash flooding cannot be managed by local and national government alone
The Greater London Authority and the borough councils, together with other parts of the public and private sectors that are responsible for managing flash flooding in the capital, launched a review.
The interim report published in July this year, recognised that a more coordinated strategy was required to raise London’s resilience against flash flooding.
It called for more investment in sustainable urban drainage systems that make it easier for rainwater to soak away. And it called for homeowners to stop paving over their front gardens. The final strategy is due to be published later this year.
The London Climate Resilience Review, which was commissioned by the mayor, Sadiq Khan, and chaired by Emma Howard Boyd, the former Chair of the Environment Agency, also called for greater investment to protect people and property against flash floods.
The Review’s final report in July recommended that the new national Government should create a Strategic Surface Water Authority for London, led by an independent and nonpolitical Chair, to “promote, enforce, and allocate funds in-line with a strategic London-wide approach to flooding”.
It also noted that without action, flood insurance for households and businesses will become more difficult to afford and access. The London Climate Ready Partnership, which brings together local government, companies, communities and academia, is launching a campaign to keep London insurable in a changing climate. On Thursday we are convening a roundtable with insurers and local government to discuss the growing threat of flooding, particularly for properties at highest risk.
The risks of flash flooding cannot be managed by local and national government alone.
Otherwise London will become a more difficult and riskier place. But a London that is sustainable, inclusive and resilient will be a great city where people can live, work and thrive.
