According to the National Infrastructure Commission (NIC), 325,000 English properties are in areas at high risk of flooding. This is defined as having a 60 per cent change of being flooded in the next year.
However, due to extreme weather from climate change and growing pressure on drainage systems from new developments, a further 230,000 properties could move into this high risk category by 2055.
It added that the increasing use of impermeable surfaces, like paving over gardens, could push a further 65,000 properties into a high risk area.
The NIC recommended reducing the amount of run-off water entering drainage systems, growing the capacity of drainage systems and creating a more “joined-up, targeted governance and funding”.
It said the amount of run-off could be limited if government strengthened legislation and standards to discourage new development connecting to current drainage infrastructure in favour of “wider uptake of sustainable systems”.
It also said the government needs to show review options for “managing the unplanned growth of impermeable surfaces”.
With existing drainage systems, it said that capacity above and below ground should be increased, and this should include nature-based solutions such as green gulleys and flood storage ponds.
Regarding governance and funding, it said that the Environment Agency and Ofwat should be more “actively involved” in delivering joint local plans and setting national risk reduction targets.
The report said that stricter controls on new property developments, as well as £12bn of investment in drainage infrastructure in the next 30 years will be necessary to prevent flooding of further homes and businesses.
The NIC said if investment in new infrastructure was taken it could move 250,000 properties out of the high risk category and improve protection for thousands more properties. Action on new developments could pull a further 95,000 properties from facing high risk of surface water flooding
Professor Jim Hall, NIC’s commissioner, said: “It’s clear that faced with more intense rainfall and increased urbanisation, we need to start taking this type of flooding far more seriously.
“The solution is clear – reducing the amount of water flowing into drains, whilst also improving the capacity of those drains. That means stopping urban creep from increasing the amount of storm water that drainage systems have to cope with and giving nature more opportunities to hold on to excess water, as well as targeted investment to ensure sewers can cope with growing pressures.”
He added: “While sustained investment is needed, the estimated additional costs are relatively modest. At least as important is a more joined-up approach to owning and acting on the problem.”
