More than half a million properties in London are at high or medium risk from surface water floods, according to a new report.
The Environment Agency study stressed that one in eight properties, which include homes and businesses, in the capital face this flash flooding threat as Britain is hit with more torrential downpours amid climate change.
The warnings come in its 44-page National assessment of flood and coastal erosion risk in England 2024.
The agency stressed: “Surface water flood risk is greater in cities where drainage systems are less able to deal with intense rainfall.
“1 in 8 (13 %) of properties in London are in areas at high or medium risk of surface water flooding.
“This is twice the rate compared to the national total, and a far higher rate than any other region.”
In total, 543,500 properties in the capital are at high or medium risk of surface water flooding.
A further 236,100 in the wider South East face this threat, out of a total of just under two million across England.
For the high risk category there are 319,800 properties in the capital, 127,900 in the South East, out of just over a million across the country.
But just 27,800 properties in London are at high risk of flooding from rivers or the sea, with 68,100 in the South East out of 367,900 across England.
“Less than 1 in 10 of properties in areas at high and medium flood risk (from rivers and sea) are in London,” the report adds.
“This is largely due to the presence of major flood defences such as the Thames Barrier.”
Londoners can check if their area is in a flood risk area by putting their postcode into this Government link.
The major new update from the agency, which comes after widespread disruption and floods from storms Bert and Darragh, shows 6.3 million properties in England are in areas at risk of flooding from rivers, the sea or surface flooding, or a combination of different sources.
The figures are up from 5.5 million in the last assessment in 2018, as the update draws on much more advanced data and modelling, including new mapping down to a 2m scale, as well as factoring in recent changes which have taken place such as new building and a worsening climate.
The analysis accounts for the impacts of climate change for the first time and warns it will lead to an increase in the number of properties in areas at risk from rivers and the sea or surface water to about eight million by the middle of the century - or around one in four homes and businesses.
About 4.6 million of the properties currently at risk face surface water floods, caused by heavy rainfall overwhelming drainage systems and causing run-off or flash flooding.
The Environment Agency said the figure was a 43% increase on the previous assessment, as a result of improvements in data, modelling and use of technology to fill in gaps in some parts of the country and give a much more accurate assessment of surface water flood risk.
Julie Foley, director of flood risk strategy at the Environment Agency, said: “Our updated assessment shows there are 6.3 million properties in England in areas at risk of flooding from rivers, the sea or surface water.
“When we account for the latest climate projections, one in four properties could be in areas at risk of flooding by the middle of the century.
Friends of the Earth campaigner, Alison Dilworth, said: “This report is yet another stark warning about the growing threat the climate crisis poses to people, homes and communities across the country - with the elderly, disabled and those living in vulnerable areas particularly in danger.”
Floods minister Emma Hardy said the report showed “too many communities” were exposed to the dangers of flooding.
“Combined with the fact that this Government inherited flood defences in their worst condition on record, it is vital we invest in protecting our communities,” she said, pointing to £2.4 billion committed over the next two years to repair and build flood defences.
