INTRODUCTION

As is now well-known, climate change due to human activity has resulted in a rise in sea levels, with recent rates being unprecedented over the past 2500 years (NASA, 2022). Specifically around New York City, the sea level now rises by as much as about one inch every seven to eight years. To put this into perspective, around The Battery in Lower Manhattan, while it took nearly 50 years for the sea level to rise six inches, scientists now forecast that it will rise another six inches in just another 14 years (Sea Level Rise, n.d.). In NYC, the water level is rising more rapidly than in some other coastal areas not only due to human-caused climate change, but also because of its sinking land combined with the slowing of the Gulf Stream, which leaves more water on the East Coast (Sea Level Rise, n.d.).

The New York City Housing Authority (NYCHA) was created in 1935 to provide affordable housing to low- and middle-income New Yorkers and is the largest public housing authority in North America. It houses over 350,000 residents within 285 housing developments throughout the city with an average family income of $24,503 and an average public housing family monthly rent of $536 (NYCHA, 2021).

The agency admits that since 1998, it’s seen a steady decline in both federal and state funding, which has resulted in its buildings’ deterioration, which now require $40 billion in major repairs (NYCHA, 2021). With this goal in mind, NYCHA 2.0, the agency’s strategic roadmap, was launched in 2018 to seek vital repairs.

After coming across a map several years ago showing areas across the city that may flood in the future, I was curious to see if any of NYCHA’s residential buildings were located in potential flood zones. The implications are that for buildings located in these flood zones, repairs should be made with this potential natural disaster in mind.

INSPIRATION

The NYC Department of City Planning’s Flood Hazard Mapper was one of my inspirations:

This interactive map shows flood hazards along NYC’s 520-mile coastline. The user types in an address, and the map then zooms in on that location, allowing them to see whether that address falls within a flood zone or not.

Instead of visualizing just one address at a time, I wanted to see all of the NYCHA developments in one view.

MATERIALS

For my first dataset, I used a shp file of “Sea Level Rise Maps (2020s 100-year Floodplain)” from NYC Open Data. A “100-year flood” – also known as a “one percent annual chance flood” – is defined by the Federal Emergency Management Agency (FEMA) as a flood that has a one percent chance of being equaled or exceeded in any given year (New York City Panel on Climate Change, 2013). The implications are that these areas have at least a one-in-four chance of flooding during a 30-year-mortgage, and therefore are considered high-risk flooding areas (FEMA, n.d.).

For my second dataset, I used a shp file of a map of NYCHA housing developments as of December 2020, also from NYC Open Data.

I created my visualization through Tableau Public, a free software with which users can create graphs, maps, and live dashboards using a variety of formats, including SHP, CSV, Excel, Google Sheets, and more. 

METHOD

I first pulled the 100-year floodplain map shp file into Tableau, pulling the “Geometry” attribute to the middle of the page in order to visualize that map. Then, I went to “New Data Source,” and added the NYCHA housing developments shp file.

At that point, I had to go to the menu option “Data,” then “Edit Blend Relationships…” in order to create a relationship between these two datasets. After that, I was able to pull the “Geometry” attribute of NYCHA housing developments shp file onto the existing map as an additional layer.

Then, in the menu, I went to “Map,” then “Background Maps,” and decided to turn on the background option for “Streets” so that no matter where the viewer looked, they would know exactly what location they were examining. However, because this new visual layer made the map now look quite busy, it made it difficult to decide what colors to assign to the two main layers.

While experimenting with colors, I started with the floodplain map. Because of the existing colors in the streets background map, such as blue, orange, and tan, I decided to go with the very different choice of a pinkish-purple to make it blatantly obvious where the flood zone was. I also moved the opacity down to 60% so that you could see the background map beneath it. Then, for the NYCHA housing developments, I settled on a bright purple to, yet again, make the buildings’ locations blatantly obvious. I also felt that it was a color that not only paired well with the flood zone map, but it was also able to stand on its own while competing with the existing colors of the background map of streets.

RESULTS

As the viewer moves the map around to various parts of the city and zooms in, it becomes obvious where some of the problem buildings are. For example, in the Redhook area of Brooklyn, one can see that all four buildings near the water fall in the flood zone while another building slightly north is partially located in a flood zone. More NYCHA developments in the 100-year floodplain are also seen in the southern Queens area of Rockaway/Arverne/Edgemere as well as the southern Brooklyn area of Coney Island/Gravesend. Other problems areas are East Harlem and the Lower East Side in Manhattan.

REFLECTION AND FUTURE DIRECTIONS

As sea levels continue to rise, the floodplain will also continue rise. As a result, FEMA and other organizations continually work together to update maps as time goes on, so it’s important to keep abreast of updates and see what changes. In the meantime, hopefully the city government is always thinking beyond just common maintenance issues for its NYCHA developments and keeping in mind such possibilities as flood damage when tending to building repairs.

REFERENCES

FEMA. (n.d.). Flood Maps. https://www.fema.gov/flood-maps

NASA. (January 2022). Sea Level. https://climate.nasa.gov/vital-signs/sea-level/

New York City Panel on Climate Change. (June 2013). Climate Risk Information 2013. https://data.cityofnewyork.us/api/assets/1F7A128D-4F0D-430C-A98E-53E44CFFCAD7?download=true

NYCHA. (March 2021). NYCHA 2021 Fact Sheet. https://www1.nyc.gov/assets/nycha/downloads/pdf/NYCHA-Fact-Sheet_2021.pdf

Sea Level Rise. (n.d.). New York’s Sea Level Has Risen 9” Since 1950. https://sealevelrise.org/states/new-york/