FLOODSHow Sponge Cities Work?
With concrete and asphalt covering areas once given over to grass and soil, the water from heavy rains has nowhere to go. Too often, that results in flooding, and cities around the world are now exploring ways to reverse this kind of urban development. And they are doing it by turning themselves into urban “sponges.” In other words, they are creating spaces and infrastructure to absorb, hold and release water in a way that allows it to flow back into the water cycle.
Though it is one of the busiest roundabouts in the east of Copenhagen, the air at Sankt Kjelds Plads isn’t heavy with the smell and texture of exhaust fumes. And rather than the roar of engines, the soundscape is characterized by the sputtering notes of long-tailed tits.
The traffic circle, which is covered with shrubs and trees, is part of a large-scale experiment to transform public spaces in the Danish capital. The idea is to make Copenhagen more “livable” by creating places for citizens to meet and habitat for biodiversity, while simultaneously creating cogs in a flood-control machine.
This transformation was sparked by the events of July 2, 2011, when Copenhagen was struck by what was dubbed “a once in a 1000-year rain.”
The massive downpour caused streets and homes to flood. And with nowhere to go, the water stayed for days. Dead rats were seen floating around the city, and later research revealed that a quarter of sanitation workers had fallen sick with blood infections such as leptospirosis in the cleanup. One even died.
Over the next seven years, this kind of “cloudburst” started to become increasingly common, with four “once in a 100-year” rainfall events recorded in that period. Costing the city at least €800 million ($865 million) in damages, it was clear to policymakers that it was time to rethink the Danish capital.
Time to Adapt to a More Sponge-Like Urban Design
Over the last centuries, the focus of urban development in places such as Copenhagen has been on creating “machine cities” that could be built up at speed and were efficient for housing, industry and the economy. But many of these cities, especially those that straightened rivers or built over floodplains, ended up meddling with the water cycle.
With concrete and asphalt covering areas once given over to grass and soil, the water from heavy rains has nowhere to go. Too often, that results in flooding, and cities around the world are now exploring ways to reverse this kind of urban development. And they are doing it by turning themselves into urban “sponges.”
In other words, they are creating spaces and infrastructure to absorb, hold and release water in a way that allows it to flow back into the water cycle.
With over 60 of its cities under redevelopment and now incorporating climate inlets, green reefs and rain gardens to hold water, China is leading the way. Jan Rasmussen, head of Copenhagen’s “Cloudburst Master Plan,” also saw potential for Denmark.
