The Environment Agency (EA) said communities near the coast or rivers could be forced to move as the country prepares to counter average global temperature rises of up to 4C.
The body said that in some cases of extreme erosion or flooding a policy of rebuilding water-damaged homes to be more resilient “may not be appropriate”, meaning “potentially moving communities out of harm’s way in the longer term”.
EA chairwoman Emma Howard Boyd said: “The coastline has never stayed in the same place and there have always been floods, but climate change is increasing and accelerating these threats.
“We can’t win a war against water by building away climate change with infinitely high flood defences. We need to develop consistent standards for flood and coastal resilience in England that help communities better understand their risk and give them more control about how to adapt and respond.
“More should be done to encourage property owners to build back better and in better places after a flood, rather than just recreating what was there before. This could involve home improvements, such as raised electrics, hard flooring, and flood doors.”
An average annual investment of £1bn will be needed over the next 50 years in England for traditional defences such as barriers and sea walls, which could be funded by a mixture of government and private sources, the EA’s new climate strategy said.
Without increased funding, flood damage to properties and infrastructure in England will significantly increase, it added. Alongside traditional defences, other measures to help communities become resilient to flooding are needed.
These could include temporary barriers, natural flood management schemes such as planting trees to slow the flow of rivers and sustainable drainage systems with ponds and areas where water can soak away into the ground.
This will deliver positive benefits for the environment as well, such as creating habitat for wildlife, experts said.
There should be effective flood warnings and emergency response will be needed, alongside designing and adapting new and existing properties to help them recover quickly from a flood, they added.
And with only one-third of people who live in areas at risk of flooding believing their property is under threat, the agency wants to build a nation of “climate champions” educating schoolchildren about the risks of floods.
The 4C warming preparations envision a future significantly hotter than the 1.5C or 2C limits agreed in international accords, which are seen as thresholds beyond which dangerous climate change will occur.
Additional reporting by PA
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