A third runway at Heathrow airport could expose residents in parts of west London and Surrey to a serious flooding risk, it was claimed yesterday.
A report commissioned by campaigners opposed to the expansion of Britain's biggest airport suggests that massive gravel extraction to build new facilities would damage a natural sponge which soaks up ground water.
Heathrow is in the middle of a flood plain, where water from the Chiltern Hills flows into the Thames.
John Stewart, chairman of the pressure group Hacan ClearSkies, said: "The worst-case scenario is that if a third runway is built, there will be extra run-off water. If that's not dealt with, we could have significant flooding."
John McDonnell, the Labour MP for Hayes and Harlington, will today call for the government to carry out a detailed flood risk assessment.
Hacan's study suggests that the Thames, Colne and Spelthorne rivers could struggle to cope with heavy rain.
The transport secretary, Alistair Darling, is due to rule by the end of the year on whether Heathrow should get a £4bn additional runway. Other options include expanding Stansted or Gatwick.
