The head of the Environment Agency must warn against building new homes in the floodplains amid floods in parts of the UK following heavy rain.
In a later speech, Sir James Bevan will say that new housing should only be allowed if it is flood resistant.
It comes when Storms Ciara and Dennis cause widespread flooding.
River levels will reach their highest level ever in Shrewsbury on Tuesday, where a serious flood alarm is in progress – which means a danger to life.
For years the Environment Agency – which covers England – has raised concerns about building houses in the flood plains and Sir James is ready to reinforce that message in his Tuesday speech.
It is expected that it will recognize that it is unrealistic to ban all development in these areas because they cover much of the country.
But he says houses should only be built there if “there is no real alternative” – and only if they are designed to be more resistant to floods.
Examples of some techniques that could be “flood-proof” homes include using the ground floor for garages only, so that people can stay safe upstairs.
Other natural methods could include planting trees, creating wetland habitats or restoring rivers that have been artificially straightened to their “natural curves”.
Sir James will also wonder if it might be better for communities to get out of harm’s way when the risks of floods – both from rivers and from the sea – become too great.
It is not new for the Environment Agency to warn of the construction of houses on the flood plains: we have been hearing this for years.
But repeating the message now, in the midst of the continuing devastation that follows Storm Dennis, Sir James Bevan hopes to attract more attention.
Like other leading figures of the agency, it wants to stimulate a national debate on how to prepare not only for the next floods but also for a future with a more hostile climate.
It raises some profoundly difficult questions as to whether it is possible to build defenses against ever larger floods.
And it is entering a sensitive territory signaling what it defines a “hard truth” that some places will become too difficult to protect from rivers or the sea.
In those cases, he says, “it might be better for communities to choose to move out of trouble.” It’s a real bomb – and something that most politicians would prefer to run away from a mile.
Severe floods hit parts of England and Wales for weeks, following two storms that brought heavy rains and strong winds.
There are still 112 flood warnings, including two severe warnings for the Severn River in Shrewsbury and Ironbridge.
More rain is expected and the levels of the rivers in Shrewsbury are expected to peak at 5.5 m on Tuesday evening, breaking the previous record.
Ann DiTella of Shrewsbury B&B Darwin’s Townhouse said 11 rooms were flooded less than a week after the water “destroyed everything in its wake.”
Meanwhile, dozens of people in Wharfage, Ironbridge, have been asked to evacuate as the Severn River could breach flood barriers.
Over the weekend, parts of Scotland were also hit by severe flooding with several vehicles blocked in Renfrewshire.
Sir James’s comments will be made in a speech at the World Summit on Water-Tech Innovation in Central London.
He will say: “Firstly, we must continue to do what we have been doing for some years: building and maintaining strong defenses to reduce the risk of flooding for communities.
“But in the face of the climatic emergency, we now need a second parallel track: to make our communities more resistant to floods so that when this happens it represents a much lower risk for people, it does much less damage and life can return. to normal much faster.
“The best way to defuse the weather bomb is better protection and greater resilience. We need both.”
The EA said it is spending £ 2.6 billion on new flood defenses that will better protect 300,000 properties by 2021, in addition to £ 1 billion to maintain existing defenses in England.
Since England has so many rivers, much of the country is an alluvial plain.
Sir James will warn that, with a growing population, the number of properties in the flood plain should almost double in the next 50 years.
Scientists warn that climate change is increasing the risk of floods because winter storms will bring more intense rains to a warming world.
England has already received 141% of its average February rainfall this month.
Some areas have seen rain for a month in 24 hours and the levels of the Colne, Ribble, Calder, Aire, Trento, Severn, Wye, Lugg and Derwent rivers have set new records in the last few days.