Climate change will impact New York City in many ways as a result of more frequent heavy precipitation, sea level rise and rising temperatures. To strengthen its resilience, New York City is developing plans that include the use of green infrastructure, a sustainable and cost-effective strategy that includes planting trees, broader use of vegetation, restoring wetlands and using permeable surfaces. And many of these projects are well underway.
ClimAID, a New York State Energy and Research Development Authority report released in November 2011 and prepared by a team led by Cynthia Rosenzweig of the NASA Goddard Institute for Space Studies and Columbia University, studied climate trends and vulnerabilities in New York State, and proposed adaptations that will enable the state to better manage the projected impacts of climate change.
The report details the multiple threats New York City faces. Most of the city’s water resource infrastructure is old and needs repair.
The combined sewer system channels wastewater from residences and stormwater runoff into the same pipes before the flow goes to sewage treatment plants. When there is heavy rainfall, however, the system exceeds its capacity and discharges directly into the Hudson River and other water bodies, resulting in “combined sewage overflows” that contain human and animal waste, and hazardous substances washed off the streets. Thirty billion gallons of polluted water flow from hundreds of pipes into New York Harbor each year, and increased precipitation will exacerbate the situation.
More frequent heavy rainfall will also trigger flash floods when the impermeable surfaces of the city cannot absorb water fast enough. Sea levels, projected to rise several inches over the next few decades, and 8 to 23 inches by the 2080s, will likely flood coastal areas and transportation systems, and overwhelm wastewater treatment plants. If the Greenland and West Antarctic ice sheets continue to melt rapidly, sea levels could rise 37 to 55 inches by the 2080s.
Temperatures in New York State could increase 1.5 to 3˚F by the 2020s, 3 to 5.5˚F by the 2050s and 4 to 9˚F by the 2080s. And as a result of the urban heat island effect—when cities are hotter than surrounding areas because buildings and streets store and reflect heat—New York City is sometimes 7˚F hotter than neighboring counties. This will mean more deaths due to heat stress and increased energy demand for cooling. Air pollution will also increase if higher energy usage must draw on dirtier sources of power to meet demand, and high temperatures mix with emissions from industry and vehicles to produce added ground-level ozone, which causes respiratory problems.
ClimAID promotes the use of green infrastructure to reduce the rapid flow of stormwater to water bodies, absorb rainfall in urban areas, protect coastal regions from flooding and lessen urban heat. Green infrastructure will also improve air quality, reduce energy use and greenhouse gas emissions, restore soil moisture, replenish aquifers and increase recreational space and property values. ClimAID’s proposals reaffirm strategies in PlaNYC, Mayor Bloomberg’s blueprint for a greener, more sustainable city, and the NYC Green Infrastructure Plan released in September 2010, which aims to improve stormwater management and water quality over the next 20 years.
The NYC Green Infrastructure Plan integrates green infrastructure with improvements to the existing wastewater system and investment in cost-effective “gray” infrastructure (pipes, tanks, tunnels, mechanical systems, etc.). Its goal is to capture the first inch of rainfall on 10 percent of the impervious surfaces in combined sewer watersheds, reducing combined stormwater and sewer overflows by 1.5 billion gallons yearly to 17.9 billion gallons a year by the 20-year mark. The overall green infrastructure plan will cost approximately $5.3 billion, considerably less than what would be needed to achieve similar results through only constructing new tanks, tunnels and pipes, etc.
Green infrastructure strategies include:
Trees - In 2007, as part of PlaNYC, the city began MillionTreesNYC, its campaign to plant one million trees in New York, and will have almost 650,000 new trees in place by 2013. The trees intercept and filter stormwater runoff, help prevent flooding, absorb pollutants from the air, cool temperatures by providing shade, sequester carbon dioxide, provide habitat for wildlife and increase property values. Trees can reduce runoff by up to 17 percent; cut greenhouse gas emissions by 1.5 to 5 percent, because they lower energy use for cooling; and decrease ground-level ozone.
Green and blue roofs – Green roofs consist of a layer of vegetation atop specially designed soil on a drainage layer. According to a 2011 report by the Center for Clean Air Policy, vegetated roofs can detain 90 percent of rainfall for storms of less than one inch and 30 percent for larger storms, holding it until it can be released gradually or used onsite. On average, they reduce runoff by 50 to 60 percent. In some cases, green roofs can reduce the surface temperatures of roofs by 30˚C (54˚F) to 60˚C (108˚F) and ambient temperatures by 5°C (9˚F) compared to black roofs, and can save 15 to 45 percent in energy consumption each year. Green roofs installed in NYC may qualify for the Green Roof Tax Abatement of $4.50 per square foot of green roof, with a maximum benefit of $100,000.
Less expensive to construct and maintain, blue roofs (without vegetation) utilize downspout valves, gutters and cisterns to slow runoff by ponding it and storing it for later non-potable uses. Blue roofs can retain 50 percent of the water that falls on them yearly.
Permeable Pavement – Replacing impervious surfaces in residential developments, public properties, streets and parking lots with permeable pavement—paving materials that allow stormwater to soak back into the ground—can reduce runoff by 70 to 90 percent. And because permeable pavement tends to be more reflective than dark pavement and more evaporative, it absorbs less heat.
Greenstreets – The city’s Greenstreets Initiative, first launched in 1996, turns concrete islands, triangles and median strips into “pint-sized parks.” These patches of green capture stormwater for irrigation and beautify communities. The initiative has received $8.5 million to create 2,760 Greenstreets by 2017; so far, 2,574 have been completed.
Swales – Swales are low-lying tracts of vegetated land on streets, around residential developments and in parks and parking lots that help slow and capture stormwater runoff, and allow it to infiltrate into the soil.
Rain Barrels or Cisterns – Water tanks that collect and store rainwater are being used at residential developments and other public properties. In 2008 and 2009, the New York City Department of Environmental Protection distributed 1,000 rain barrels in Queens and Brooklyn. The Solaire Building in downtown New York, which collects rainwater in a 10,000-gallon cistern for cooling, low-flow toilets and irrigation, has reduced its potable water use by 50 percent.
Wetlands – Healthy wetlands provide protection against storm surges and erosion, slow and retain stormwater runoff, naturally filter pollutants from water, and are important habitats for wildlife. Tidal salt marshes, the wetlands most commonly found in NYC, are in decline, and will be further threatened by higher temperatures, droughts and sea level rise, leaving coastal communities more at risk of storm and flood damage. Protecting existing wetlands, restoring degraded wetlands and creating new ones are key to protecting the city from sea level rise. Engineered wetlands can also help manage stormwater in parking lots and parks.
The city, the Army Corps of Engineers and other partners are restoring the Elders Point marshland in Jamaica Bay, where once there were 16,000 acres of salt marsh lands. They have already restored over 80 acres and plan to restore 350 to 400 acres in total.
Greening vacant lots, brownfields and landfills – Vacant lots can be greened with rain gardens, where vegetation is planted in depressions to capture rainfall, and green gardens. Green remediation will be used to restore brownfields—land previously used for industrial purposes that may still be contaminated by hazardous wastes—with tree planting and the creation of parks and community gardens. Former landfills will also be turned into public parks. Once the world’s largest landfill, Fresh Kills on Staten Island is being developed into an environmentally sustainable park almost three times the size of Central Park.
The New York City Green Infrastructure Plan predicts that, “every fully vegetated acre of green infrastructure would provide total annual benefits of $8,522 in reduced energy demand, $166 in reduced CO2 emissions, $1,044 in improved air quality, and $4,725 in increased property value.”
The Department of Environmental Protection is already spending millions of dollars on green infrastructure demonstration projects, including grants to local environmental groups and academic institutions. The projects will be evaluated to see if their strategies will be effective in other locations. The 2012 Green Infrastructure Grant Program has up to $4 million available for demonstration projects.
In 2010, a $389,187 grant was awarded to the Columbia University Urban Landscape Lab for a Greenstreets stormwater capture system in Rego Park that will replace impermeable surfaces with 2,500 square feet of permeable pavement. Landscape architect Kate Orff, an assistant professor at the Columbia Graduate School of Architecture, Planning and Preservation and the project’s principal investigator, said the pilot project has been slow getting off the ground because of difficulties in contract negotiations. She is confident, however, that they will begin building this year and open in 2013.
“It’s great that everyone is embracing green infrastructure,” Orff said, “But the devil is in the details where mechanics and policy must come together.” Although the actual mechanics of green infrastructure are relatively simple, dealing with the city’s regulations and policies is not. For example, even planting a tree requires navigating the complex regulations governing underground utility pipes. But Orff is upbeat, “It’s in these pilot projects where the difficulties are identified and overcome. Where the broad topic of green infrastructure hits the specifics of the city is the exciting part. Ultimately, the process will become more streamlined.”
In October 2011, the NYC Department of Environmental Protection and the New York State Department of Environmental Conservation reached a draft agreement allowing the city to move ahead with its green infrastructure plan, laying the groundwork for one of the largest green infrastructure programs in the nation.