Why concrete + rain = flash floods

By Jeremy Plester

In towns and cities, flash floods are a growing problem. The concrete jungle can’t soak up rainwater, so in heavy downpours it has nowhere to go except into drains, overloading them and setting off flash floods.

A movement in Canada and the US called Depave is tearing up concrete and asphalt in local neighbourhoods and replacing it with gardens to soak up rainwater and help prevent flooding. And although Depave is largely unknown in Britain, there’s a growing need for similar action here.

Gardens in Britain are vanishing at alarming speed under slabs of paving stones, decking and asphalt. Front gardens are being turned into car parking spaces – nearly 5m front gardens in the UK are now completely paved over and more disappear each year – and London has seen the biggest destruction of front gardens. Meanwhile, back gardens are increasingly being turned into patios, with a lot less maintenance needed.