To Prepare for Climate Change, Copenhagen Is Building Parks That Can Turn Into Ponds - CityLab

COPENHAGEN, Denmark—At first glance, the square known as Tåsinge Plads doesn’t look much different from other parks in Copenhagen. But there are hidden features that make Tåsinge Plads part of this seaside city’s plan to survive the effects of climate change.

During heavy rains, the flowerbeds fill with water and wait to drain until the storm runoff subsides. The upside-down umbrellas collect water to be used later to nourish the plantings. And clever landscaping directs stormwater down into large underground water storage tanks. Above those tanks are bouncy floor panels that children love to jump on—when they do, the energy from their feet pumps water through the pipes below.

Just a few years ago, this square was paved with asphalt and dominated by parked cars—a small grassy area was used more as a toilet for dogs than as a park. Now, it’s the cornerstone of a plan to make the surrounding area of Saint Kjelds into what planners here are calling the world’s first “climate-resilient neighborhood.”

The tarmac has been torn up and the greenery reduces the urban-heat island effect. More parks like it are being built to purposefully turn into small ponds during heavy rains, allowing them to capture and retain water on site until the drainage system has capacity to handle it. During the worst deluges, certain streets with raised sidewalks will become “cloudburst boulevards,” creating a Venice-like cityscape of water channeled safely through the city until it can empty into the harbor....

Copenhagen isn’t alone in re-thinking its relationship with water. Two years ago, Rotterdam unveiled Benthemplein Square, an urban space with three concrete basins that intentionally fill up to store large amounts of water during storms. In the United States, Philadelphia has embarked on a $2.5 billion, 25-year effort to install thousands of rain gardens and permeable surfaces to allow rainwater to seep into the ground rather than run off into sewers and streams.

Copenhagen is advancing on a similarly massive scale. The city has recently been hit by two so-called “100-year flood” events, first in 2011 and then again in 2014. The Intergovernmental Panel on Climate Change predicts that this sort of extreme weather will become increasingly frequent in Denmark, with heavier downpours (as well as more periods of drought). Sea-level rise is a separate but related threat—according to research from the Niels Bohr Institute, the waters around Copenhagen could rise by up to 1.6 meters (more than 5 feet) in the next 100 years.