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Using Green Infrastructure to Reduce Combined Sewer Overflow in Queens, New York
Teri Mendelsohn SUMAK4205 GIS for Sustainability Dara Mendeloff 10 December 2015
Introduction and Background
• Ordinarily, rain and snow run into sewers, combine with sewage and get treated at wastewater treatment plants (WWTPs) to remove pathogens and solid waste
• Heavy precipitation overwhelms WWTPs and excess runoff, combined sewer overflow (CSO), is diverted to outfalls and released into waterways, contaminating them
• Water quality continues to be problem in Flushing Bay, Queens
• NYC is deploying green infrastructure (GI) to reduce CSO
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Goal and Objectives
Questions • What kinds of GI were installed? • Where were they placed? • Why were they installed in those locations?
Focus: Rain barrels accounted for 96% of GI installed in 12 neighborhoods near Flushing Bay, 2008-2012 Hypothesis: GI was placed in areas that tend to flood Possible causes • Highways and boulevards • Topography • Drainage
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Area of Study Neighborhoods around Flushing Bay, Meadow and Creek Queens, New York
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Green Infrastructure Types and Locations
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Green infrastructure was placed in 11 of the 12 Queens neighborhoods. Forty-six percent of installations were in Forest Hills and Rego Park. Ninety-two percent were rain barrels.
Highways and Boulevards
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Seventeen highways and boulevards with four or more lanes crisscross the study area.
Green Infrastructure Near Roads Within 400 yards of boulevards and highways
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Forty percent of GI installations were within 400 yards of highways. Ninety-four percent were within 400 yards of boulevards with four or more lanes.
Green Infrastructure Near Roads. Cont’d. Within 400 yards of boulevards and highways
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Ninety-six percent of installations were within 400 yards of both highways and boulevards with four or more lanes.
Elevation Feet
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Eighty-four percent of GI installations were placed 7.7 feet above sea level or higher. Ten percent (five installations) were at lower elevations in Rego Park and Corona, on either side of I-495/Long Island Expy.
Conclusions
• Many variables contribute to CSO and GI
• Rain barrels are a cheap and easy-to-install, albeit indirect, way to buffer flooding and CSO during peak precipitation
• NYC placed them – In Forest Hills and Rego Park (46%)
– Near highways and boulevards with four or more lanes (96%)
– On hills to divert runoff that could not be absorbed fast enough by soil and vegetation (84%)
– In low-lying area in Rego Park and Corona surrounding I-495/Long Island Expy that is prone to flooding (10%)
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Next Steps/Future Work
• Has flooding in Rego Park and Forest Hills been reduced as a result of the barrel program?
• Has water quality in Flushing Bay improved as a result of the barrel program?
• Given different amounts of precipitation, how much buffer capacity can rain barrels provide?
• What kinds of GI have been installed where since 2012? • What formal (documented) and informal methods does the city use
to determine placement of GI? • What programs are in place for installing GI at other large-scale
industrial and commercial sites, e.g., pervious pavement, green and blue roofs at LaGuardia airport, box stores like Home Depot, etc.?
• Where are the WWTPs on Flushing Bay located? What fine-grained data on water quality in Flushing Bay is available? Does it correlate to proximity to WWTPs?
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GIS Methods
• Hand tagging
• Select by location
• Extract by mask
• Select by attribute
• Clip to visual extent
• Buffer, union and dissolve
• Clip (analysis)
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Data Sources
New York City LION Single Line Street Base Map http://www.nyc.gov/html/dcp/html/bytes/dwnlion.shtml, downloaded 12/4/15 New York City Neighborhood Boundaries and Neighborhood ID numbers Columbia Digital Social Sciences Center (https://www1.columbia.edu/sec/acis/eds/dgate/studies/C1301/data/NEIGHNYC.zip), downloaded 11/12/15 New York City Department of Environmental Protection Green Infrastructure http://maps.nyc.gov/doitt/nycitymap/template?applicationName=GREEN_INFRA, downloaded 11/8/15 U.S. Geological Survey NED 1/3 arc-second contour map http://viewer.nationalmap.gov/, downloaded 11/30/15
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