Communities in coastal areas and those at risk of flooding in the UK may have to move as climate change increases and accelerates the threat of floods, Environment Agency bosses have claimed.
The organisation's chairwoman Emma Howard Boyd said the country "cannot win a war against water" by building ever-higher flood defences.
She said homes hit by flooding needed to be "built back better" with improvements such as hard flooring and raised electrics - and that some communities may even have to be helped to move to escape the risk.
It comes as the government published its long-term strategy for managing the risk of flooding and coastal erosion - which predicted at least £1bn a year may have to be spent to keep at-risk homes and communities safe.
It is planning for the potential of up to 4C of warming, well beyond the 1.5C or 2C limits which have been agreed internationally and are seen as thresholds beyond which dangerous climate change will occur.
The Environment Agency (EA) also predicts that climate change and population growth are set to double the number of properties built on the flood plain over the next 50 years.
Ms Howard Boyd said urgent action was needed to tackle more frequent, intense flooding and sea level rises driven by rising temperatures, and called for more resilient homes and infrastructure.
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.
Without increased investment, flood damage to properties and infrastructure in England will significantly increase, the EA strategy says.
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.
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.
And with only a 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 youngsters through the curriculum about the risks of floods.
Launching the strategy at Brunel University in London, Ms 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."
But she warned: "In some places, the scale of the threat may be so significant that recovery will not always be the best long term solution. In these instances, we will help communities to move out of harm's way."
Environment minister Therese Coffey said the government was already providing £2.6bn over six years to deliver more than 1,500 projects to better protect 300,000 homes.
She added that the government will be launching a call for evidence to inform future action towards flood and coastal erosion risks.
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