Hurricane-Proof Park How Green Stormwater Infrastructure Can Mitigate Flooding
Allie Lapporte, LASN
According to a sustainability report from the American Planning Association, "Green infrastructure is a community 's natural life support system, the ecological framework needed for environmental and economic sustainability." Considering the storms and hurricanes that seem to hit coastal cities in the United States almost yearly - data from NOAA shows that 7 hurricanes strike the country every four years, while three major hurricanes hit every five years, and FEMA states that one major flooding event occurs every year - one aspect of sustainability that cities are now looking for in design is stormwater mitigation and resiliency. Green spaces help soak up and filter rain where it falls rather than allowing it to run off hard surfaces like paved roads into storm sewers and, ultimately, into waterways - along with the garbage, bacteria, and other pollutants it has picked up along the way. Parkpeople.ca, a Canadian website devoted to promoting the benefits of parks in cities, estimates that "absorbent landscapes, like parks, can reduce runoff by 8 to 10 times compared to impermeable surfaces like roads or parking lots."
One park that was completed in the summer of 2018 may have some answers when it comes to managing stormwater flooding. Hunter's Point South Park, located in Queens, N.Y., and designed by SWA/Balsley, in partnership with WEISS/MANFREDI and infrastructure designer ARUP, exemplifies a strategy that can help clean up after major storms and flooding disasters.
A Sustainable Park The 5.5-acre park reestablishes an acre of wetlands, a return to the site's pre-industrial history and a contribution to the site's resilience. With both low and high marshes planted, the new wetlands enable shoreline bank erosion control and sediment stabilization. With an expanded plant palette, the wetlands also enhance water quality and promote wildlife and fish habitation.
Phase two of Hunter's Point South Park opened in June, but the first half of the resilient park had already been tested. As phase one neared completion in 2012, Hurricane Sandy and its 4-foot storm surge flooded the entire area. When the storm was over, the water drained right back out into the river at a pace the sewer system could handle, leaving the park intact.
The park is also a new model for waterfront resilience, with a "soft" approach to protecting the water's edge from floodwaters. Instead of concrete walls and buttresses guarding the plot from the river, this park works with the river. Twice a day, as the high tide rolls in, Hunter's Point South Park becomes a marsh.
Low Tide / High Tide Between the riverside path and the park's main promenade, a small creek develops through the long grasses-tall and native-built to survive the brackish onslaught. Part of the park, a peninsula in low-tide times, becomes an island when the river comes up. Hunter's Point South Park's relationship with the river is dominated by slow, rocky descents into the sea, and a tide that works with the landscape. A continuous meandering causeway, elevated slightly above the river, offers a walk along the river's edge and protects nearly 1.5 acres of newly established wetlands.
A New Kind of Park The park design transforms abandoned industrial land opposite Manhattan into a new model for urban waterfront development. The park anticipates the inevitable flooding patterns and rising water levels of the East River while leveraging its views to establish a multi-layered recreational and cultural destination and environmental habitat that completes the design team's collaboration.
"It's a new kind of park," said lead landscape architect Tom Balsley of SWA/Balsley. "Hunter's Point South is at once resilient infrastructure and contemplative retreat-a dynamic, living platform with extraordinary power to touch the daily lives of so many people."
Green Infrastructure in Parks According to the Environmental Protection Agency, in a 2017 report on how to incorporate more sustainable practices into parks, there are several reasons other than flood mitigation to incorporate green infrastructure into park design. Green infrastructure can enhance recreational value, create attractive park features, enhance social and environmental equity and reduce maintenance. When addressing how to maintain an acceptable level of safety along with storm mitigation techniques, the EPA report suggests that landscape architects design stormwater elements that minimize the risk potential for park users such as eliminating trip hazards, adding crushed stone paths, or designing boardwalks or viewing platforms. Designers should also create water areas with the public in mind and limit access to gently sloping bank areas around water features by adding natural screens and barriers while allowing public access where it can be controlled or monitored by park staff. Hunter's Point South achieves this level of safety with specific trails that lead pedestrians around water areas, and with its boat-like viewing platform that allows park-goers to see the river without getting too close to areas that might be flooded during high tide.
Stormwater Mitigation in Parks The NRPA, in its Green Infrastructure Resource Guide, lists a few different ways to manage stormwater in parks. These include bioretention, bioswales, constructed wetlands and more. Hunter's Point South Park mainly relies on constructed wetlands for stormwater runoff. However, designers should consider several different sustainable techniques when considering a stormwater-resilient park.
The NRPA recommends analyzing a park's location and context before incorporating green stormwater infrastructure. Not every park could support every type of stormwater mitigation system, and it is important to find the right fit in order to create the most sustainable park possible in a specific location.
A Sustainable Guide Some sustainability-based design standards that the Hunter's Point South Park maintains are: designing higher than one thinks flood waters could possibly reach, making it difficult, but not impossible, for flood water to get into the park area and making it easy for water to flow back into bodies of water, but not into sewers.
For areas that are in dire need of stormwater mitigation in their infrastructure, these design ideas could change the way cities recover when a huge hurricane or rainwater event hits.
Conclusion Between soft barriers and purposefully flooded wetlands, Hunter's Point South Park exemplifies green stormwater infrastructure that has been proven to combat flooding and stormwater damage. Using the park as a guide and with the aid of several government and association resources, park designers may be able to implement storm resilient aspects into parks around the country