“It went through the door, it went through [the garden], and it came out through some people’s floorboards. I have a concrete floor, so I’m lucky. But it came very quickly.” Flooding destroys irreplaceable memories – from university, from travel, from work abroad – but Smith resigns himself to such events, keeping his home from flooding whenever possible. he. “After the fourth time,” he said, as we walked into his living room, “I explained that this was the worst. And with climate change, things are going to get worse and worse and worse.”
As unpredictable weather and heavy rains become the norm, cities like London face increasing flooding. England’s Environment Agency estimates that 235,000 residential properties in London alone are currently at risk of surface-water flooding. Here, as elsewhere, common building materials such as asphalt, brick, and concrete, the foundations of urban development, have proven incompatible with a changing climate. London, a city of just over nine million, is particularly vulnerable. It has a poor Victorian drainage system and antiquated methods of water collection, such as underground storage tanks that are both expensive to maintain and unadaptable to rainfall. It also uses up to three times more concrete than other UK cities. To planners here, the need to better integrate flood resilience into urban infrastructure is increasingly apparent.
Integrated flood management — a mix of hard and soft defense methods — will be key to London’s ability to cope with extreme weather. As a city that will be partially underwater by the year 2050 under current climate projections, the infrastructure must be able to withstand and mitigate floods. Rain gardens – shallow holes in the ground filled with plants such as ferns, soft rushes and other native trees – are being established across the city to help take the rising pressure from its drainage system and to improve climate resilience, collecting run-off from streets, roofs, and other hard, gray surfaces in the city.
ON A HOT MORNING IN early June in Leytonstone, East London, not far from Rosannah Smith’s home, jackhammers whine as they tear up the pavement of a residential street, a sign of progress toward natural infrastructure. . At the end of the road, workers are building a “sustainable urban drainage system,” or SUD, where rain gardens and trees will replace pavement and parking lots. In SUDs, water flows into shallow depressions filled with mud and drought-resistant vegetation, overflowing the soil that is heavy with hard and coarse aggregate.
“SUDs are more sustainable and effective in reducing the risk of surface water flooding compared to traditional drainage systems,” said Simon Crowther, a water and environmental manager based in London and Nottingham. These systems “mimic nature and the natural catchment of an area by directing rainfall and water near where it falls.” The city’s existing systems, he said, were not designed for long-term sustainability. “Instead, they just divert water elsewhere, which often causes problems in these areas, along with areas where rainwater falls.”
Rain gardens, a key element of more sustainable systems, work as an absorbent layer between the city’s impervious surfaces and traditional drainage systems. “They will store excess water, divert it safely without affecting neighboring areas, dilute the water before it returns to waterways, and allow it to seep into the soil naturally,” Crowther said. .
Where cities find themselves at a higher risk of flooding, rain gardens offer a level of fortification: reintroducing constant, natural drainage in green spaces lost to urban development, as well as to alleviate the causes of inner city pollution and to make natural spaces accessible. In these corners of London, planners are building “sponge cities,” like those built in China. Gradually, they followed the wisdom of a leading sponge city designer, Yu Konjian, who famously promoted green solutions to the problems of the gray city. “You can’t fight in water,” said Yu. “You have to leave it.”
Waltham Forest, the borough that Leytonstone is home to, has been building a thriving network of rain gardens since 2015. Planners here are now launching new spaces as part of a wider local initiative, called the Business Low Emissions Neighborhood. Sustainable drainage has a big role to play in responding to changing weather patterns, Clyde Loakes, a Labor Party councillor, says as we walk through the neighbourhood. Pointing to a row of houses with block-asphalt facades, Loakes describes the effect of removing vegetation from residential streets. “Our Victorian drainage system can’t handle the amount of water that’s coming down today because so many people are paving their front gardens, whether it’s to put away their cars or just take out rubbish bins,” he said. “Water will find its way into a property if possible, and even if you can only do a couple of millimeters extra time and drainage. [with gardens]then that will help.”
In the nearby town of Walthamstow, where the gardens are more robust, they provide unique pockets of biodiversity. The rain gardens here have become mini urban jungles, where children are bound by tall reeds and wild flowers on their way to school.
Rain gardens also work without flooding, cleaning the air, making neighborhoods more walkable, and reducing vehicular traffic, which is of great benefit to areas like East London, known for its oton level of air pollution. In Leytonstone, rain gardens have been built alongside small parks, cycling paths, and other green features, limiting car parking and encouraging low-emission transport options. “In the morning,” said Loakes, “you can only see people walking in the middle of the road with their children, people riding scooters and bicycles. It’s a joy.”
