A hard rain’s a-gonna fall: why are we ignoring the rising risk of surface water flooding?
Mill Stream House in Stadhampton, Oxfordshire, is named after the brook that runs beside the 18th-century property. Mindful of the flood risk, the original builders laid the base of the house 3 feet above the brook. The home’s coach house, built around the same time and converted into a home in the mid-1980s, was on ground level, however. When Richard Pryor and his wife started renting it in 2016, it was hard to imagine the home would ever flood. The Environment Agency website, which based warnings on the water level of the brook 3 miles upstream at Chalgrove, showed the danger was remote.
Water levels above 55cm placed low-lying local land at risk — when out walking their dog, the Pryor family would sometimes pass waterlogged fields. Local properties were at risk when levels surpassed 81cm. But even when the brook reached 1.22m in February 2014, the highest level recorded by the EA, the former coach house wasn’t touched. It had never flooded since the owners, Pryor’s parents-in-law, bought the home in 1984.
But on January 8 last year, following several days of heavy rainfall, Pryor and his wife woke at 2am to barking from the kitchen. The dog was standing in 4 inches of water, which was leaking through where the skirting boards met the vinyl tiles. Unable to absorb any more run-off, the ground was pushing water up from below. The Pryors’ home was being flooded from within.
Homes throughout the village had flooded and residents looked for a cause. They accused the council of having inadequate storm drains and the Environment Agency of not dredging the brook enough (as well as the surface water flooding, many houses nearby had also been flooded when the brook broke its banks). Others blamed new home building in Chalgrove and redoubled their efforts to block government-backed plans for a 3,400-home town on Chalgrove Airfield.
The Pryors tried to stay sanguine. Neither could find an obvious culprit — and what difference would it make if they did? “It had never happened before,” says Pryor. “We chalked it up to being very unlucky.”
The scale of risk from surface water floods like the Pryors’ — caused by rain falling faster than the surrounding ground can absorb it, and distinct from flooding from rivers or the sea — is just coming into view. When the Environment Agency updated its model — using better data and adding the effects of climate change — the number of properties at risk in England jumped by 43 per cent on a year earlier, to 4.6mn. Uncertainties around forecasting mean the number may be even higher. As they assimilate the elevated risks, insurers are withdrawing from flood coverage fast, scuppering home sales, particularly in high-value areas of London. But too few householders are taking steps to protect their homes.
On February 4, when UK environment secretary Steve Reed announced a £250mn boost to flood defence spending over the next two years, the big-ticket items on the government’s list aimed at tidal and river flooding — £43mn for a tidal barrier in Somerset, another £35mn for flood prevention along Derby’s River Derwent. This is partly because they have a larger financial impact than those from surface water, and individual floods are bigger and more destructive. The announcement followed the latest spate: as rivers across the Midlands and the North West reached record levels at the very end of last year, 1,600 homes had been inundated by New Year’s Day. Reed posed for photos atop the Ipswich Flood Barrier, a £67mn coastal defence completed in 2019.
“People’s first response is always, well, if you must live near a river or the sea, what do you expect?” says Mary Long-Dhonau OBE, the flood resilience champion who has toured the UK providing support and advice for flood victims for the past 20 years. In fact, properties at risk from surface water outnumber those in danger from rivers and sea by two to one. When Long-Dhonau presents this fact, it is frequently dismissed as nonsense: “People just refuse to accept that houses can flood from too much rain.”
Public reluctance to take surface water flooding seriously contrasts with the approach of insurers, who are withdrawing from the market. The number of policies ceding flood protection to Flood Re — the government insurer of last resort — increased by 289,000 last year, a rise of 9 per cent. Surrendering business from hard-won customers is a good sign that the risks outweigh the benefits.
Insurers also know the future could be far worse than predicted. According to Oliver Wing, chief scientific officer at flood risk modeller Fathom, the climate models that saw the EA’s predictions jump 43 per cent in December are already out of date. Like all models, they rely on data from previous years, when the climate was more stable. “We know that intense spells of rainfall are becoming more frequent as the climate warms, but the changing climate also makes historical data less relevant, so they are becoming harder to predict,” he explains. Pryor’s confidence in his flood risk reading at Chalgrove looks increasingly out of place.
Unlike an approaching coastal storm, or the clear delineation of a river’s flood plain, it’s a host of man-made variables that can determine where a deluge of rainwater ends up. Capacity in the sewage networks; the location of roads, curbs, drains and culverts (and councils’ success in keeping them free of litter or debris leaves); new building projects that have replaced fields with impermeable tarmac and concrete: all these factors affect where and how quickly water from a heavy rainstorm — or even a burst pipe — will drain.
To put it another way: you may be busy worrying about the river that flows through your village when the real danger is your neighbour’s new tennis court or the patch of garden you have just paved over to extend your drive.
The nationwide insurer pullback masks a much faster retreat in London, which is now affecting sales. The successive flash floods that followed heavy rainfall in July 2021, striking expensive neighbourhoods such as Notting Hill, landed insurers with £281mn of property payouts, according to Perils, the insurance industry database. The claims also equipped insurers with granular data about which homes are at risk. With models now updated and payouts complete, insurers look a lot like rats deserting a sinking ship.
Clare Blakely specialises in insuring high-value homes for UK broker Weatherbys Hamilton. Half of her 69 London clients last year had their flood insurance backstopped by Flood Re, up from one in five in 2022.
This time last year, London buying agent Guy Meacock had never heard of a home sale scuttled by a flood insurance problem during his 20 years in the business. Then, just days before a client was expecting to exchange on a £5mn house in Wimbledon, they told him their current insurer had refused to cover the new home.
Scrambling to keep the sale on track, Meacock’s insurance broker called more than a dozen insurers, including high-street names and specialists for high-value homes. One after the other, they refused. “They weren’t even interested in a discussion,” he says. The home, which had a basement, had been built in 2010 — too recently to qualify for Flood Re’s standard cover. Two years earlier, the broker explained, insurers would have been lining up to write a policy; now no one would touch it.
A week or so later, Meacock established that Flood Re would provide an exemption because the home replaced one of comparable size on the same site. But by then it was too late: the client, who had experienced surface water flooding on a previous home in Germany, had pulled out. “They had spent nearly £40,000 on surveys and legal fees — the seller another £20,000,” he explains.
Meacock forecasts the collapse of more such sales over questions of insurability, with Wimbledon particularly vulnerable. He now asks prospective buyers to check that a home can be insured as soon as they are interested rather than — as is currently typical — shortly before exchange.
“The landscape [in London] is rapidly changing, but clients haven’t realised, agents aren’t talking about it, and most [conveyancing] lawyers are largely unaware,” he says.
The National Infrastructure Commission, which advises the government, wants more action on preserving open ground for water to drain through. The commission’s Rob Mallows points to provision in 2010 legislation allowing local councils to insist developers develop drainage to manage surface water run-off, rather than connect to public sewers. But the government has not yet triggered the powers. “It’s not that difficult to design [flood resiliency], if you do it from the start,” he explains.
Taking up paving in your garden to help it drain will help (so, for city dwellers, will choosing a home near a park). At the Chelsea Flower Show last year, the Flood Resilient Garden, sponsored by Flood Re, included dense planting to slow water flow. An elevated deck and mound provided ground for both plants and humans in need of well-drained soil; a stream channelled water into a feature pond; neighbouring tanks doubled as ornamental pools to provide additional capacity for rainwater.
Long-Dhonau’s website floodmary.com is a trove of advice. She recommends white goods and electrical sockets raised off the floor; external doors that form water-resistant seals when closed; a separate electricity circuit for the upper floors; self-closing airbricks for cavity wall and underfloor ventilation — because you don’t want to be out in a storm at 3am with a headtorch trying to fit an airbrick cover.
© Source: Householders’ guide to flood resilience, 2023 (floodmary.com)
There are sections on emergency measures: using gaffer tape to make doors watertight, or keeping decorators’ trestles in storage, in order to prop furniture up on them and prevent damage from the water line. One picture shows the four legs of a kitchen table inside Wellington boots.
But many suggestions — washable flooring rather than carpets, plastic skirting boards — emphasise the uncomfortable reality of surface water flooding: if the weather is severe enough, your home will probably succumb regardless.
“Nothing will protect you when a storm sits over London for days dumping an intense amount of rain,” says Wing.
Last September, nine months after the flood, and three months after the refit had been completed, life at the Pryors’ 18th-century coach house had returned to normal. Earlier that summer, they had bought a second dog to cheer themselves up. Now, in the orchard of the two-acre shared garden, they once again hosted lunch parties, baking pizza in the outdoor oven.
A drier than average summer ended wet. On the last day of August, TV presenter turned local farmer Jeremy Clarkson took to X, with a post containing five expletives followed by the word “rain”.
But Pryor wasn’t worried. The Environment Agency still rated the chance of yearly surface water flooding at less than 1 in 1,000. And, with 2 acres, there was hardly a shortage of ground for water to drain.
Then, on September 24, gentle drizzle disturbed another alfresco family meal. It grew stronger over several days. This time, Pryor was alert to the signs. As the drains on the main road clogged up, water crept back up the lane and under the front gate. The downstairs toilet started making a gurgling noise. Pryor turned to his wife: “Shall we have the dogs up here tonight?”
What followed the second flood was like a scene from Groundhog Day. Up came the tiles, out went the carpets, in came the dehumidifiers. Their insurer was as surprised as they were. One contractor told Pryor: “We’ve never come back to the same home in such a short space of time.”
Pryor is steeling himself for further repeats. “Once in 50 years is bad luck, twice in a year looks like bad news,” he says. “If I were a betting man I’d put a pint on it happening again in the next 12 months.”
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