In September of this year, New York City experienced a severe storm that inundated its streets with more than 7 inches of rain in less than 24 hours, causing a number of roads to close, cars to submerge, and buses to get trapped. This event again highlighted the city's old infrastructure's inability to handle fast and heavy rainfall. As climate change intensifies, experts warn that such extreme weather events will become increasingly frequent. This vulnerability is especially concerning in densely populated urban areas such as New York City, where flooding risks increase due to the large amounts of impervious surfaces.
In response to this imminent challenge, New York City’s Office of Environmental Protection released in 2022 a long-term resilience plan for cloudburst storms in New York City. A significant part of the plan involves strategies to reduce the amount of stormwater that enters the sewage system at once. It involves the implementation of features that allow water to seep into the ground, such as gardens and green belts, as well as structures designed to hold rainwater, like water squares, tanks, and dry ponds. Their pilot plan includes location-specific initiatives that would serve a dual purpose: providing relief from flooding while also offering public amenities and open spaces for use during rain-free periods.
The NYCHA South Jamaica Houses pilot project was created as part of a regional cloudburst master plan for the South Jamaica portion of Queens in response to its increased flooding from rainstorms. It involves the extensive implementation of outdoor public spaces that would serve as flooding prevention infrastructure. In addition to providing public amenities, these outdoor spaces would reduce the need to add below-grade infrastructure. On top of the implementation of bioswales, the plan outlines the use of playfields, portions of streets, and parks as a network of interventions that can hold and drain stormwater in a controlled manner—detaining stormwater in public spaces to then slowly release it, either by infiltration into the ground or through piped connections to the city’s existing storm sewer system.
Copenhagen faced similar challenges in the 2010s when cloudburst storms led to frequent flooding in the Vesterbro district. The re-design of Enghaveparken presented an opportunity to handle extreme rain while updating the look of what had become an under-utilized park. Designed by Third Nature, COWI, and Platant, the park was adapted to hold significant rainwater capacity while preserving its historical simplicity. Excavation and the construction of a low wall, which doubles as a bench during dry spells, enabled the park to store up to 800,000 cubic feet of rainwater. The re-design of the park also included adding a series of amenities throughout the park and new experiences of recreation and interaction with water.
Another innovative method implemented in Copenhagen was the creation of “Climate Tiles.” Created by Third Nature, with IBF and ACO Nordic, these transform sidewalks into water collectors in dense urban areas. They catch water from roofs and redirect it towards green areas and water banks, which allows it to seep into the soil. Third Nature, in collaboration with the Copenhagen Municipality, built a pilot in 2018 located in the Nørrebro neighborhood in Copenhagen. This approach promises to not only manage stormwater effectively but also enhance the urban environment, turning gray streets into vibrant outdoor living spaces.
In Bangkok, Thailand, Chulalongkorn Centenary Park by LANDPROCESS is another example of a flood mitigation project serving as a public amenity. Opened in 2017, the Chulalongkorn University developed 11 acres of land to serve as a public park and as infrastructure to reduce urban flood risks in a flood-prone city. On a 3-degree gradual incline, the park collects, treats, and holds water. It comprises green roofs, wetlands, detention lawns, and retention ponds. Additionally, it also has three underground tanks that store rainwater from the green roof and store it to irrigate the park. At the park's lowest point is a large retention pond, which, during severe flooding, can double in size and store excess water. Beyond flood mitigation, Centenary Park also offers a series of multi-purpose areas, including an herb garden, meditation area, playground, earth amphitheater, and bamboo garden.
As the impacts of climate change continue to manifest in the form of extreme flooding events, urban areas around the world must adapt in the fight against climate change. Creating new types of public spaces, and making water a semi-permanent feature of their urban fabric. The examples showcased here demonstrate that such adaptations can not only serve as effective flood mitigation infrastructure but also enhance the quality of life for communities in densely packed urban areas. New York City cloudburst plans, mirroring "sponge city" global precedents, offer the dual promise of risk mitigation and the creation of more vibrant public spaces. Considering the urgency of climate change and its effects, their quick implementation will not only be of immediate public benefit but an imminent necessity.
