The third reason, according to the expert, is London’s lacking drainage system.
The Victorian-era system has not been designed to handle the amounts of water being pumped into it.
And due to budget limitations, Dr Edmonds-Brown said local authorities are unable to maintain or improve them.
The expert added: “To combat this, sustainable urban drainage systems (known as SUDs) should be installed in all new developments and they should be adequately funded.
“We should also use permeable materials more, such as permeable tarmac and asphalt, and we should continue to expand and maintain our drainage system.
“The drainage system was built in the Victorian era and cannot cope with the huge increase in population.”