As reported in the Financial Times earlier this month, research has found the number of front gardens being paved over in Britain has tripled in 10 years – and the Royal Horticultural Society has warned that paved gardens exacerbate flood problems.

Three million more front gardens have been completely paved over since 2005, making 4.5m in total, according to the RHS.

The society first recorded the dwindling of front gardens in a survey 10 years ago but its follow-up research, carried out this year, confirmed its worst expectations. “We’re very concerned about the loss of green space,” said Sue Biggs, RHS director-general. “Everything we feared was happening then has escalated. One in four gardens in the country is now paved over — a shocking statistic in a nation of gardeners,” she said.

Concreting or paving increases the risk of flooding, the RHS said, since the impermeable materials typically used to cover over a front garden cause water to run off into drains rather than be absorbed by the soil.

The society is calling on owners to consider permeable paving and to use more potted plants when gardens are already paved.

Rising car ownership has been one of the main factors behind the loss of gardens, the RHS said. An average 12 cars to every 10 households was recorded in the 2011 census, up from 11 per 10 households in 2001. The proportion of households with more than one car also rose over the period. “It’s a very difficult problem when now households regularly have two or more cars,” said Ms Biggs.