RAINWATER MANAGEMENT
INTO EVERY GARDEN, A LITTLE RAIN MUST FALL
Rain gardens are a growing market sector. BMJ finds out what makes a rain garden different and how merchants can maximise opportunities.
T
his is the United Kingdom. It rains. A lot. This fact, plus ever more stringent planning policies, is driving an expansion of the sustainable drainage systems (SuDS) market, which means that builders – whether whether working on new- builds, extensions or new driveways – must consider how to manage surface water run-off in a more sustainable way. Specifically, the key drivers behind this expanding market are the adoption of Schedule 3 of the Flood and Water Management Act in Wales and the Sewer Sector Guidance in England last year. As a result, the definition of SuDS is evolving and the suite of solutions that utility companies are able and willing to adopt is now much broader. Within the Sewer Sector Guidance in particular, a hierarchy of drainage options is included, with a preference for approaches that see water collected for use or discharged into the ground for infiltration. In new build developments for instance, this could be considering both domestic solutions at a plot level, as well as longer, linear SuDS systems. Equally, builders and landscapers should think how to incorporate plants and trees to collect excess water from a domestic driveway. Charlotte Markey, green urbanisation innovation manager at Polypipe Civils & Green Urbanisation says that means rain gardens an ideal option for both these applications. “There’s a huge opportunity for merchants to add additional sales across both conventional rainwater and landscaping markets, and for new build and retrofit projects,” she says. Traditionally, rain garden design has been limited to a small area of plants and shrubs intended to hold and soak away rainwater run-off and these are usually ‘plugged in’ to existing drainage networks, collecting water from roofs, driveways or lawns. But rain gardens can be used much more widely. “When combined with optimised and integrated tree pits and engineered swales, rain gardens help create a more biodiverse solution to sustainable drainage. This more integrated approach also has a more tangible impact on the volumes of water removed from the combined sewer network, which also reduces the risk of flooding,” Markey explains.
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“When planning their offer, merchants can also consider ways to create a unique selling point for their business and alleviate the time pressures on builders and developers through off-the-shelf, plug and play approaches to green infrastructure solutions. By packaging up products, they can provide a ready-to-go planter, for example, that can be delivered to site in volume and installed with ease.
Fresh thinking Rain garden planning
“As the market for rain gardens expands, now is the perfect time for merchants to review their rainwater, SuDS, landscape and drainage portfolios to ensure they remain competitive and meet the evolving needs of builders, developers and landscapers.
“Typically merchants might associate geocelluar systems for shallow applications with engineered settings. However solutions like Permavoid – a breakthrough in shallow invert rainwater attenuation – are ideal for domestic applications too, providing a permeable sub-base replacement,” she adds. As well as providing source control of excess water and water treatment, the added advantage of such systems is their ability to support the growth of plants and trees. This enriched environment supports a healthy ecosystem, helping to neutralise carbon emissions and, in turn, creates a beautiful, landscape for the end user.
These new sub-base systems can be installed under rain gardens and SuDS tree pits within hard landscaping, or in new build gardens where soil quality is poor and buyers want to be able to sustain plants and trees. Shallow geocelluar solutions can be used to create a rain garden in a planter with a disconnected down pipe or installed to support a rain garden in a driveway that generates high run-off volumes.
“Higher capacity geocelluar systems for deeper applications – like Polypipe’s Polystorm range for example – can be used outside their conventional setting to optimise swales, rain gardens and rills where surface flows converge and greater volumetric control is needed,” Markey continues.
“With such systems already within merchants’ water management ranges, all that’s required to maximise sales for rain garden applications is fresh thinking and an understanding of how to support product selection with their customer.” BMJ
Polypipe Permavoid and
Permafoam cells have been
installed on a busy London street as part of four new rain gardens,
adding amenity and biodiversity to the streetscape.
In order to compensate for the loss of permeable green space that would have alleviated the risks of excess stormwater, Polypipe supplied a unique SuDS geocellular solution at Melina Road, a busy residential street in Hammersmith, which includes a local school and a public open space. 2,345 Permavoid cells were installed to create four separate storage tanks to sit beneath new rain gardens. The tanks will provide 88m³ of rainwater storage. Each of the Permavoid tanks feature a top layer of Permafoam cells to upwardly irrigate the rain garden above.
www.buildersmerchantsjournal.net March 2021
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