It may be the Main Avenue show gardens that get all the headlines during the week of RHS Chelsea Flower Show, but this year, one container garden is highlighting an important – and often overlooked – message.
According to new research by Flood Re, the organisation behind the gold medal-winning Flood Re: Contain the Rain garden, millions of homeowners in the UK could be 'sleepwalking into a flooding crisis'. Flood Re says 82% of garden owners in the UK think their plot would cope with heavy rainfall, but almost one in three don't realise paving and other hard surfaces can boost the risk of flooding – and just 3% consider flood risk when planning their garden.
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While gardens with a high proportion of planting and permeable surfaces allow rainwater to soak into the ground, spaces with paving and other hard materials increase the amount of surface runoff, putting extra pressure on drains. In fact, just 5mm of rain in a 20-square-metre garden can create 100 litres of runoff – the equivalent of a full bathtub of water.
When combined with rainwater runoff from roofs and gutters, and multiplied across a residential street, gardens with a large proportion of paving boost the risk of flooding – especially with climate change bringing increasingly unpredictable weather events.
According to Flood Re, the average flood repair bill is now more than £30,000, so changes to how we design our gardens can save homeowners money.
“Intense rainfall alone doesn’t cause flooding – it’s all about what happens to rain when it hits the ground," said Dr Peter Melville-Shreeve, associate professor at the University of Exeter. "Hard surfaces like our driveways and rooftops disrupt the natural hydrological cycle and stop water soaking in.
"As we pave over our green spaces – a process we call ‘urban creep’ – more rainwater rushes straight into our sewers. Slowing water down at source – in green spaces, gardens and around homes – can be one of the simplest and most effective ways to manage rainwater and reduce downstream flood risk.”
At RHS Chelsea Flower Show this year, the Flood Re: Contain the Rain garden – one of the show's balcony and container gardens – showcases how garden design can hold and slow rainfall.
“This garden is about showing that you don’t have to choose between beauty and resilience," said the designer John Howlett. "By using planting, permeable materials and thoughtful design, you can create a space that looks great but also works much harder when it rains. It’s about turning gardens into places that don’t just shed water, but actually help manage it.”
The Flood Re: Contain the Rain garden showcases several clever features, including remodelled containers underneath to store drained surface water. At the push of a button, it is then released to dampen topsoil to help with water retention during warmer months.
“Our garden provides a blueprint for everyday people to help flood-proof their gardens," said Flood Re’s head of corporate affairs, Kelly Oster-Coyle, "from including a high density of trees and plants to help absorb surface water, to ensuring damp topsoil to maximise retention and avoid run off.
“Plants such as Astilbe 'Deutschland' and Astilbe 'Dark Side of the Moon' feature heavily in the garden, highlighting that gardens can be both beautiful and practical.”
See the Flood Re: Contain the Rain garden at the Chelsea Flower Show this year. Read more about it in our guide to this year's balcony and container gardens.
