This document summarizes a study analyzing the use of green infrastructure (GI), primarily rain barrels, to reduce combined sewer overflow (CSO) into Flushing Bay in Queens, New York. The study found that GI was primarily installed in Forest Hills and Rego Park, within 400 yards of highways and major boulevards, and at elevations of 7.7 feet or higher to intercept runoff. Specifically, 96% of GI consisted of rain barrels placed in locations that tend to flood during heavy precipitation to help buffer flooding and CSO. The document concludes by discussing opportunities for future analysis, including evaluating the effectiveness of the barrel program and exploring additional GI strategies.

1. Using Green Infrastructure to Reduce Combined
Sewer Overflow in Queens, New York
Teri Mendelsohn
SUMAK4205 GIS for Sustainability
Dara Mendeloff
10 December 2015

2. 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
1

3. 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
2

4. Area of Study
Neighborhoods around Flushing Bay, Meadow and Creek
Queens, New York
3

5. Green Infrastructure
Types and Locations
4
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.

6. Highways and Boulevards
5
Seventeen highways and boulevards with four or more lanes
crisscross the study area.

7. Green Infrastructure Near Roads
Within 400 yards of boulevards and highways
6
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.

8. Green Infrastructure Near Roads. Cont’d.
Within 400 yards of boulevards and highways
7
Ninety-six percent of installations were within 400
yards of both highways and boulevards with four or
more lanes.

9. Elevation
Feet
8
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.

10. 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%)
9

11. 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?
10

12. GIS Methods
• Hand tagging
• Select by location
• Extract by mask
• Select by attribute
• Clip to visual extent
• Buffer, union and dissolve
• Clip (analysis)
11

13. 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/NEIGH
NYC.zip), downloaded 11/12/15
New York City Department of Environmental Protection Green
Infrastructure
http://maps.nyc.gov/doitt/nycitymap/template?applicationName=GREEN_IN
FRA, downloaded 11/8/15
U.S. Geological Survey NED 1/3 arc-second contour map
http://viewer.nationalmap.gov/, downloaded 11/30/15
12

14. Contact
Teri Mendelsohn
tm137@columbia.edu
13