The recent heavy rainfall has shown that run-off can swiftly overwhelm systems and cause surface water to build up in low-lying areas.
Speaking at the Royal Geographical Society conference, Dr Alistair Geddes from the University of Dundee said he had modelled at-risk areas in Glasgow, Belfast and Luton.
"Existing flood risk assessments are based on the number of properties at risk as opposed to the number of people," he said. "This approach downplays the impact on people, and in particular potentially vulnerable groups such as the elderly. We estimate that around two million urban residents are exposed to this kind of flood risk and that this applies more so to several vulnerable social groups.
"The number at risk is expected to increase by more than half, to 3.2million people, by 2050, largely the result of regional population growth, although changes in precipitation caused by climate change will also be important."
Meanwhile, home owners hit by flood damage across the UK could be needlessly spending thousands of pounds on repairing ruined homes because they do not understand what is covered under their buildings insurance policies, says drainage expert David Hayes, CEO of Drain Claim.
“I am certain the gut reaction of many home owners to flood damage is to fix it as soon as possible but they shouldn’t be paying for any repairs without speaking to a drainage expert first and identifying the exact cause of the damage and whether they have a valid insurance claim,” said Hayes.
“Blocked, cracked or collapsed drains which cannot cope under a sudden deluge of rain are often the real culprits behind flooded homes. Without addressing these homeowners run the risk of a repeated damage to their properties. Having the drainage system inspected is vital before beginning any cosmetic repairs on a property."