The walls are alive in Victoria, London, where a new 21-meter-high vertical garden located on the side of a hotel contains 10,000 plants and 16 tons of soil—all in the name of flood protection. Commissioned by the Rubens at the Palace Hotel, the living wall consists of robust pollinating plants and is irrigated by up to 10,000 liters of harvested rainwater that can reduce the risk of surface water flooding in the area. "It's a 350-square-meter green sponge," explains David Beamont, environmental and sustainability manager at the Victoria Business Improvement District (BID)
The vertical garden, planted on the road-facing side of the Rubens, was chosen after Victoria BID’s green audit in 2010 identified locations that would most benefit people and wildlife.
According to the wall designer, Gary Grant of Green Roof Consultancy, living walls are frequently abandoned due to cost—typically $600 to $800 per square foot. "There are a limited number of locations where living walls can be retrofitted," Grant says. "The detailed design process was about six months, although I had been thinking about the wall for two years." Grant built a similar living wall in Westfield, Shepherd's Bush in 2008.
Living walls have been criticized historically, he says, because they use filtered water and don’t contribute to water sensitive urban design. However, the latest living wall designed by Grant is a sustainable drainage system (SUD) in green disguise. The wall captures rainwater from the roof of the hotel in dedicated storage tanks; the rainwater is then channeled slowly through the wall to nourish plants, simultaneously reducing surface water on the streets below. "The plants themselves will take up rain too, so the rain doesn't fall on the street below," says Beamont.
Flood prevention is a serious problem for the area. "There are now around 534,000 properties in London on the Thames floodplain, and one in four in London are at risk of flooding," says Beamont. This is largely because of the low absorbency of urban surfaces.
The London Subway has closed multiple times due to flooding problems, with local businesses losing thousands of pounds as a result. The Mayor of London, Boris Johnston, hopes to promote more SUDs in the area through the Drain London project, including green roofs and rain gardens, according to Grant.
Victoria’s big green sponge doesn’t just soak up water. It’s also an air-filtering, biodiversity powerhouse. "Vegetation can trap microscopic pollutants known as particulate matter, high levels of which have been shown to cause respiratory illnesses." Beamont says. "Vegetation can also disperse heat more generally so [living] walls help to reduce local air temperatures and tackle the urban heat island effect."
During the design process, Grant picked out native ferns, English ivy, geraniums, strawberry and primroses for the living wall, using the Royal Horticultural Society’s pollinators list as a guide. "My approach is to use native species in natural associations, however sometimes it’s not practicable because of problems with availability or a lack of visual interest or late flowering," he says. "It’s still necessary to choose plants that are known to thrive in living walls, or are likely to thrive in living walls, and are suited to the aspect and microclimate."
Construction of the vertical garden took around 12 weeks, although there were problems with access, the erection and dismantling of scaffolding, and a burst water main causing a road closure. "Weather was exceptionally hot during the building—workers were getting heat stroke before the vegetation was installed," says Grant.
The Victoria BID has many more green ideas in the pipeline. The cobbled over space outside the head office of John Lewis, a large U.K. department store, will be transformed into a rain garden in a few weeks time. The garden was designed by Nigel Dunnett, one of the two principal plant designers for London's Olympic Park, along with John Lewis.
The district also recently converted a turfed space outside The Queen's Gallery at Buckingham Palace into a biodiversity garden, with design assistance from Dunnett and the Palace. "We're undertaking research with a government department (Defra) and two universities (University of York and the London Metropolitan University) to help us understand what benefits improving spaces for nature brings for the economy and the people who live and work in urban spaces," says Beamont.