A small container garden at this year’s RHS Chelsea Flower Show highlights an overlooked risk: UK homeowners could face a £30,000 flood repair bill by ignoring how their gardens manage rainwater.
Most gardeners remain unaware their choices increase flood risk. Research by Flood Re, the organisation behind the gold medal-winning Flood Re: Contain the Rain garden, revealed 82% of UK garden owners believe their plots can handle heavy rainfall. Yet nearly one in three don’t know that paving and other hard surfaces worsen flooding. Only 3% factor flood risk into garden planning.
Hard surfaces like driveways and patios block rainwater from soaking into the ground. Instead, it flows off, overwhelming drains. A 20-square-metre garden generates 100 litres of runoff from just 5mm of rain—equal to a full bathtub. Combined with water from roofs and gutters, the issue spreads across neighbourhoods.
Flood Re’s data shows the average flood repair bill now exceeds £30,000, making garden design a financial concern.
The Flood Re: Contain the Rain garden, designed by John Howlett, offers solutions. The display uses permeable materials, dense planting, and underground storage to hold and release water gradually.
“Intense rainfall alone doesn’t cause flooding—it’s what happens when rain hits the ground,” said Dr. Peter Melville-Shreeve, an associate professor at the University of Exeter. “Hard surfaces disrupt the natural water cycle. As green spaces disappear under paving, more rain rushes into sewers. Slowing water at its source, like in garden design, can cut flood risk downstream.”
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Remodelled containers in the garden store drained water. At the push of a button, the system redistributes it to keep soil damp during dry periods without adding to runoff.
“This garden proves beauty and resilience aren’t mutually exclusive,” Howlett said. “With the right plants and materials, gardens can manage water instead of shedding it.”
Flood Re’s head of corporate affairs, Kelly Oster-Coyle, described the display as a “blueprint” for homeowners. Key elements include high-density planting to absorb water and damp topsoil for maximum retention. Plants like Astilbe ‘Deutschland’ and Astilbe ‘Dark Side of the Moon’ show flood-resistant gardens can still look striking.
The display remains open at this year’s Chelsea Flower Show, offering visitors a practical example of small adjustments that help.
Flood Re’s findings show the need for awareness. Homeowners who overlook garden design may pay a steep price.
