Flooding: UK government plans for more extreme rainfall

The UK’s new flood defence plans anticipate significantly higher extreme rainfall, after new research was published as part of the government’s National Flood Resilience review.

The government, which had been criticised for not taking full account of the impact of climate change in driving up flood risk, will now plan for 20-30% more extreme downpours than before.

The review, prompted by severe flooding in recent winters, also found that 530 critical infrastructure sites, such as water and telecoms, are at serious risk from floods, each potentially affecting at least 10,000 people. Utility companies have pledged to have new protection in place by the end of the year.

The government’s official climate change advisers recently warned that flooding could cause a cascade of emergencies by knocking out energy, transport, water and communications links.

The review allocates £12.5m for more temporary defences, such as barriers and pumps, at strategic locations around the country. By this winter, the government said, four times more temporary barriers will be available.

“Last winter we saw just how devastating flooding can be. This review sets out clear actions so we are better prepared to respond quickly in the event of future flooding and can strengthen the nation’s flood defences,” said the environment secretary, Andrea Leadsom.

Ben Gummer, Cabinet Office minister, said: “The government has made clear that we expect water and telecoms companies to work ever closer together to improve their preparation and response to flooding, making sure lifelines such as mobile phone masts and water treatment works continue to function.”

Bob Ward, policy director at the Grantham Research Institute on Climate Change at the London School of Economics and Political Science, said: “This review was launched because the government was caught out by [recent] flooding. It deserves credit for admitting that ministers have previously misunderstood and significantly underestimated the probability of flooding.

“However, it is disappointing that the government chose to ignore surface water flooding during the review, even though it poses a threat to more properties in the UK than does coastal and river flooding,” he said.

Lord Deben, chairman of the Committee on Climate Change, the government’s official advisers, welcomed the review but said it fell short of what was needed: “As well as implementing short-term measures, such as better protecting key sites, we need a new and comprehensive, long-term strategy to address flood risk in this country.”

Friends of the Earth campaigner Guy Shrubsole said: “This review suggests a sea-change in government understanding of floods, but its recommendations are a wash-out. £12.5m for temporary flood defences is a drop in the ocean when the review concludes that winter rainfall could increase by up to 30% in future in parts of the UK, [which] will put thousands more homes and businesses at risk.”

Paul Cobbing, chief executive of the National Flood Forum, which represents flood communities, welcomed the review but said its narrow scope did not tackle the community-level work required. He said preventing every flood is impossible and adapting homes to cope is vital: “It is really important to engage with people about the residual risk in the right way, so that they own that risk. There are elements of government that understand this and there are other elements that clearly don’t.”

Councillor Martin Tett, from the Local Government Association, said: “Councils will need significantly more support from government to help prepare for the possibility of further flooding.” Council flood funding was cut by 50% in 2015.

The review asked the Met Office to develop new plausible extreme rainfall scenarios. It added 20-30% to recently recorded extreme events, a figure it expects will mean only a 10% chance of worse rain in the next 10 years. “When we used the Environment Agency’s detailed models to predict the flooding associated with these extreme rainfall scenarios, we discovered (unsurprisingly) that it, too, was worse than anything we have seen to date,” the review states.

The Met Office modelled over 11,000 monthly rainfall scenarios, many times more than the set available from real-world observation in recent decades. “This allowed us to identify several hundred extreme monthly rainfall events that are greater than current existing rainfall records, but are regarded as plausible for the current climate - what might be termed ‘black swan’ events,” it said in a statement.

The review found that a 20% heavier extreme rainfall event in Carlisle would lead to 280 more homes flooding, on top of those that were inundated last winter, while 400 more homes would flood in Mytholmroyd and a similar number in Hebden Bridge. A “stress test” in the review of a plausible extreme tidal surge affecting Great Yarmouth found that “it would mean an additional 1,700 properties would flood compared to the December 2013 tidal surge, when 20 properties were flooded”.

One approach little mentioned by the review is to use natural methods to slow the flow of water and tree planting has been shown to have prevented flooding at Pickering in North Yorkshire over Christmas, at a time when heavy rainfall caused devastating flooding across the region. A separate back-to-nature trial in Holnicote, Somerset, has also showed promising results.

Brenda Pollack, from Rewilding Britain said: “The government has missed an opportunity. With the focus on cities, valuable work in rural areas to mitigate against floods will take a back seat. But restoring natural, varied landscapes helps absorb flood waters and is more cost effective than expensive flood barriers.”

Speaking before the report’s publication, former floods minister Richard Benyon said farmers could to be paid to hold back floodwater under a post-Brexit rural payments system: “There is an opportunity now to completely rethink rural policy, and flood protection can come in as part of the way we support farmers and see farming as doing a public good when it protects communities from flooding.”

Flood defence spending was cut sharply by David Cameron’s coalition government but partly reversed after severe floods in the winters of 2013-14 and 2015-16. In March’s budget, a £700m boost was pledged, meaning some English cities and towns that had been left without planned flood defences by the cuts are now getting the projects. The north of England, devastated by winter floods, is getting at least £150m of the new money, giving better protection for thousands of homes.

The Guardian revealed in 2012 that 294 projects in line for funding were left stranded after the heavy cuts and exposed a series of places that were later flooded. These included Leeds and Kendal, which were submerged in last winter’s storms. Both places will now get improved defences. The new money is being funded by an increase in insurance premium tax.

The government had been warned by a series of official bodies in recent years that flood risk was rising due to inadequate spending and was costing billions of pounds in damages. Government scientists have long warned that more severe flooding is the greatest impact of climate change in the UK.

Floods already cause £1bn of damage every year on average but the risks are rising as climate change leads to more intense rainfall, bringing floods to places not currently in danger. The number of households at significant risk of flooding will more than double to 1.9m by 2050, if the global temperature rises by 4C.