When Philip and Elaine Marco sat in their Mercedes to drive home from their son’s 40th birthday party, it was the last time anyone saw them alive. Their car didn’t crash. They drowned in it.
A storm on 26 August 2023 had suddenly caused severe flash flooding on a section of Queens Drive in Liverpool that dips under a railway bridge. It had already flooded four times that year but the city council had not installed any warning signs.
The couple, aged in their mid 70s, had no idea how deep the water was. In the darkness, they drove in and their vehicle’s engine cut out.
Hydrologists warn the risk of incidents like this is growing in the UK because climate change is making deluges of rain heavier and more common.
Researchers and campaigners claim action has been weak at every level of government for many years, both to prevent flash floods and alert people when they occur.
Flash flooding is particularly dangerous because it can occur suddenly in urban streets that have never flooded before and are miles from rivers or the sea.
It’s a year-round threat to heavily paved areas where excess water cannot seep away – but it becomes more likely after long periods of drought like Britain is experiencing this summer, when soil in parks, gardens and grass verges is too hard to absorb water quickly enough, meaning drains fill up fast.
“It can literally strike anywhere,” says Jess Neumann, associate professor of hydrology at the University of Reading. “It happens very quickly and it’s very hard to forecast, so it takes people by surprise and it’s very hard to plan for.”
Although no extreme rain is forecast in urban areas over the next fortnight, it may be more likely this autumn when a “super El Nino” weather pattern could affect conditions here.
Fatalities from urban flash flooding – also called surface water flooding – have been relatively rare in the UK, but experts fear the possibility of a genuine disaster is growing.
UK has ‘dodged a bullet’… so far
One potential risk is if extreme rainfall inundates basement flats in the middle of the night, when people are asleep and may only wake when it’s too late to escape.
When Hurricane Ida hit New York City in 2011, 11 of the 13 deaths occurred in apartments below ground.
“There’s a real risk of that happening in major British cities,” says David Shukman, visiting professor at the Grantham Research Institute on Climate Change and the Environment.
The former BBC Science Editor, author of The Response: A Story of Fire and Flood in Britain’s New World of Extremes, believes the UK has “really dodged a bullet” so far. He is “appalled at the lack of readiness” at national and local levels.
There were also victims in basement flats in the Valencia region of Spain in 2024, which killed 229 people in total, but all kinds of homes can be affected.
About 4.6 million properties in England are now at risk from surface water flooding, according to the National Flood Risk Assessment published in 2024, with hundreds of thousands more buildings vulnerable in Scotland and Wales.
Three times more properties are at high risk of flash floods than from rivers or the sea, warns the Flood Forecasting Centre, and eight in every 10 homes now at high risk of flooding are located in towns and cities, according to the National Housing Federation.
The National Risk Register outlines how the reasonable worst-case scenario – “a large flood event in a metropolitan area” – would cause “significant damage to homes and businesses” and may lead to “sinkholes or landslides”, with residents needing evacuation and shelter.
It warns that “the exact location of the most intense rainfall would not be known in advance”. Although people can register to receive official warnings about river flooding, flash flooding is too unpredictable for them to be issued.
Dangers can be hyperlocalised, with one street at risk while another around the corner is not. “There’s not really accurate threat mapping because a dropped kerb can mean the difference between your property flooding or not,” says Neumann.
Of the 20 constituencies in Great Britain most at risk, 14 are in London. An official assessment of the capital’s reasonable worst-case scenario, produced in 2020, warned 108,000 properties could be affected, with “over 40 fatalities” and 314,000 people displaced.
Elizabeth Rapoport, chair of Flood Ready London, was shocked when her area of Walthamstow, north London, flooded in 2021, when the equivalent of two months’ rain fell in two hours.
“It feels as if the water comes out of nowhere,” Rapoport explains. “We had drains surcharging, it was like fountains coming up out of the street… The speed can overwhelm a place.”
It creates long-term problems, too. “My children’s school was knee deep in contaminated water, that took three years to repair.”
London mayor Sadiq Khan has sent leaflets to 45,000 basement flats afterwards with advice on signing up for Met Office weather warnings, checking drains and preparing evacuation kits.
The national register says the probability of serious flash flooding in a major city over the next five years is between 1 and 5 per cent, but the weather can make statistics look silly.
When a flood hit Liverpool’s Queens Drive in June 2023, it was described as a “one in 412-year event”, yet the incident that killed the Marcos at the same spot happened just two months later.
Senior barrister Anthony Metzer KC represented the Marco family at the inquest last year when a coroner found Liverpool City Council “failed to appreciate the risk to life” on the stretch of road.
“There had been four recent flash floods in exactly the same area”, says Metzer, yet the council “did absolutely nothing”.
The local authority was reluctant to close such a busy highway to improve a drainage system that was more than 100 years old.
“What was really unbelievable is that there were no warning signs at all,” says the barrister. “They’d been lucky that nobody had died when cars were stranded in previous flash floods.”
Metzer is worried that if other cash-strapped councils have a similar attitude, then there is a “clear risk” of further “risk to life or injury” around the country.
The council has since installed signs, sensors and flood barriers on Queens Drive, with its chief executive Andrew Lewis offering “deepest condolences” to the couple’s family, but relatives are pursuing a civil claim against the authority.
The need for ‘sponge cities’
Emma Howard Boyd, a former chair of the Environment Agency who also now serves at Grantham, caused a stir in 2021 when she warned we must “adapt or die” over flood risks.
Like many experts, she says councils should install more “sponge city” design features such as permeable pavements, roadside garden areas and urban wetlands, allowing more rain to be absorbed.
She appeals to the public: “If you want to park your car in your front garden, don’t tarmac over the whole thing.”
Howard Boyd wishes ministers would do more to encourage these to be introduced. “Other parts of the world have either made it more expensive to pave an area or offer incentives to de-pave areas,” she added.
A government spokesperson said it is investing at least £10.5bn in flood defences over the next decade. Much of this is to guard against river and coastal flooding – but they added: “We have also extended funding for the Rapid Flood Guidance Service to provide local responders with timely information if there is a risk of flash flooding.”
It’s the job of local councils to manage flood risks from surface water. But the Government says it is strongly committed to improving the implementation of sustainable drainage systems in property developments.
Neumann argues there needs to be more proactive policies. “I don’t understand why new houses are not being built with a storage system that water can go into if there’s a flood,” she says.
While it’s right to improve defences against threats from rivers and the sea, as well as avoiding more construction on floodplains, Neumann says these measures are irrelevant for flash floods.
She is frustrated that many officials still don’t realise how the risks have changed and grown. “I had a meeting with a load of planners the other week who were still referring to research from 20 years ago. It’s moved on so much since then.”