NYC Flood Map: Investigation of 5 Neighborhoods

"Building by building, block by block. It's a game of inches"
The Fight over Flood Maps across New York City

There are hundreds of thousands of New York City residents living in a flood zone limbo, and this is a story about them. They reside outside of the current FEMA 100-year flood zone (created in 1983 and only slightly updated since), but inside various versions of proposed flood maps from both FEMA and the City. Many in this "grey area" saw extensive damage from superstorm Sandy, yet resist incorporation into flood zones, hoping to avoid the costly flood insurance and property renovations that incorporation would require.

On one hand, we know that the 1983 and subsequent flood maps grossly underestimate flood risk and entirely fail to account for climate change. But residents, developers, and activists in these neighborhoods see things differently, advocating instead for a generally conservative classification of flood zones. Avoiding the very safeguards that would reduce long-term flooding costs may seem irrational, but the process of creating flood maps is an inexact exercise in probability. One report estimates that some flood map predictions have uncertainty levels as high as 40 percent. Given this, the fight over flood zones makes more sense: if the predictions are so imprecise, why should one resident buy flood insurance while their neighbor does not? For many, these costs are not insignificant: according to one resident, "if you get flood insurance, you can't pay your bills."

We focus on several diverse neighborhoods throughout the City - Tribeca, Alphabet City, Greenpoint, Red Hook, and Gowanus - all of which faced significant Sandy damage and now may see a substantial change in flood zone boundaries, impacting thousands of blocks of residential and commercial property. How are these residents approaching the prospect of a new flood map and all that comes with it? Could these updated boundaries have prevented damage from Sandy? How do the views of residents mesh with those of politicians and scientists? Which blocks are fighting back, and how many inches can they win?

Case Study #1: Tribeca (1:4000)
FloodBoundary_BuildingFootprint_tribeca2-01

We chose Tribeca because that neighborhood had the largest cluster of buildings flooded during Hurricane Sandy that were outside of the 100 year flood zone within Manhattan. Tribeca is one of the wealthier areas in New York City (and even in Manhattan) and is home to a significant amount of recent real estate investment and development. If we are positing the theory that pressure from neighborhood leaders and financial interests might have influenced the drawing of the 2007 100 year flood line, this may be a good starting point.

Case Study #2: Red Hook (1:4000)
FloodBoundary_BuildingFootprint_redhook4-01

Red Hook was completely inundated by Hurricane Sandy, but it was not altogether unexpected—Red Hook is essentially a peninsula, surrounded by the Upper New York Bay, the Red Hook Channel to the west, the Erie Basin at its southern tip, and the Gowanus Canal to its east. After Hurricane Sandy, Red Hook banded together as a community and today has an extremely active disaster response and resilience network run by its own residents (including emergency public wifi, etc.). Only a few buildings were inundated by flood waters during Hurricane Sandy outside of the planned 100 year flood zone.

Case Study #3: Gowanus (1:4000)
FloodBoundary_BuildingFootprint_gowanus1-01

Like Red Hook, it is an extremely susceptible area to flooding because of its proximity to the Gowanus Canal. There was fairly significant “unexpected” flooding on all sides of the canal. In contrast to Red Hook, there has not been as much community activity in response to the flooding.

Case Study #4: Greenpoint (1:4000)
FloodBoundary_BuildingFootprint1_Greenpoint3-01

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Both of these areas experienced massive amounts of unexpected flooding, more so than any other area in NYC that we can immediately see. Both of these areas lie at the intersection between Newtown Creek and the East River, and both “flood routes” bypassed certain areas including parks and pooled in a cluster. (We suspect topography/slight changes in elevation may be the reason for this, but have yet to dive deep into those specifics.)

Case Study #5: Alphabet City (1:4000)
FloodBoundary_BuildingFootprint_AlphCity-01

Alphabet City, an area with a relatively high amount of NYCHA housing, experienced massive flooding and relatively few houses flooded that were outside of the 100 year flood zone. Quickly looking at a map also shows a less dense concentration of businesses than in the areas immediately neighboring it (East Village/Lower East Side). This economic makeup and the fact that the flooding was largely expected makes for an interesting contrast to Tribeca. (In addition, Alphabet City and Tribeca are on nearly the exact same latitude.)

*A/N We are still in the process of working on the graphics, including getting a detailed topographical map of NYC in order to better understand the flooding patterns within our site.

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