NYC Flood Maps - Preliminary Research

Flood Maps’ “Grey Area”
There are several areas in NYC that have been at times in flood zones and at times outside of flood zones. There were nearly 10,000 buildings outside of flood zones pre-Sandy that were flooded, and many of these are now included in current flood zones (ProPublica). 2013 preliminary post-Sandy maps from FEMA doubled the number of individuals within flood zones in NYC, though the City disputed these zones (NY Observer). Other areas were previously within flood zones, but through recalculation and political intervention may no longer be. What makes these places different from each other? What makes them different from other (similar) parts of New York.

The city’s Chief Resilience Officer said that those who live in disputed areas should expect to be in limbo for years. This “limbo” has taken many forms: a Long Island representative encouraged his constituents to buy flood insurance before changes were implemented (Press Release). Other caution against buying real estate until the new maps are formalized, and those whose homes were damaged by Sandy are unsure of whether to stay or leave (Postmedia).

Sandy - How wrong were the flood maps? Why were they wrong? Would things have been different if they weren’t so wrong?
Sandy was an obvious turning point in how New Yorkers, policy-makers, and FEMA thought about flood maps. ProPublica investigated the impact of inadequate flood maps on the damage caused by Sandy and found it to be significant: there were large swaths of the city outside of the flood zones that faced serious flooding. Could this flooding have been prevented with more accurate flood maps? And did FEMA know the degree of the problem (ProPublica)? There were certainly more advanced technologies that FEMA could have used (Lidar, more advanced computer models), but budget limitations prevented full implementation (NewsDay). There were other unknowns, however. What was the impact of climate change? Was Sandy a statistical anomaly (after all, flood maps are just probability estimates - there is no “upper bound” of flooding that is implied, just that flooding above a certain bound is unlikely).

Also of note: the City actually had more advanced, updated flood maps before Sandy struck, using data that the city had paid to collect itself. These maps, however, had not gone through the time-intensive review process, so they were unreleased at the time Sandy hit. Can we simulate a world where these maps had been released? Would anything have been different (New York Times)? And by proxy, how much can more accurate maps really do to prevent flood damage?

What are the factors that influence the use and creation of flood maps?:
Citizens play an interesting and sometimes significant role in the creation of flood maps. In 2015, that influence came from a diverse group of New Yorkers. Politicians certainly took up the fight, with Representatives from areas impacted by new flood zone maps lobbying for more conservative boundaries that matched the independently contracted maps from the city (Meeks Press Release, Addabbo Press Release). Real estate developers had very specific concerns; some citizens hoped for more inclusive boundaries; other hoped for less inclusive boundaries. There is also an ethos at play: the City’s post-Sandy housing recovery strategies emphasized rebuilding in vulnerable locations as opposed to converting them to open space. This ‘tough’ strategy of Build It Back argues that New Yorkers’ are ‘tough’ and the City doesn’t turn its back to the water. As a result, the City has pushed conservative flood maps and waterfront investment resulting is a dramatic increase in both lives and dollars at risk to future flooding events. Instead, some hope to rely on so-called resilient codes to mandate upgrades to new and substantially-upgraded construction along with other soft-infrastructure projects to protect these people and investments (Crain’s, MetroPolitics, Cuomo 2013 State of the State Address).

All told, we know that the new New York flood maps will be contentious: “the remapping battle will be fought building by building, block by block. It's a game of inches” (ClimateWire, New York Times).

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