For years, Long Island homeowners, like their counterparts across the country, have turned to maps produced by the Federal Emergency Management Agency to understand how susceptible their properties are to flooding. But FEMA’s maps have been criticized by climate experts as underestimating risk because they don’t account for the effects of climate change and haven’t been updated for decades because of a lack of funding.
New research provides grist for that argument. First Street Foundation, a nonprofit research and technology firm working with the University of Pennsylvania, Massachusetts Institute of Technology, Johns Hopkins University and others, found that New York has 2.6 times as many properties at substantial risk of flooding than have been identified by FEMA.
The federal agency lists 239,000 New York properties as facing substantial risk. First Street, which uses current climate data and maps some areas that FEMA does not, found an additional 376,500 properties at risk, a gap the firm projects will reach 449,800 by 2050. Nationally, First Street found 70% more properties at risk of flooding than did FEMA.
The local story is a tale of two counties. In Nassau, First Street listed about 900 fewer properties at risk than FEMA, a 1.9% difference, but it counted nearly 29,000 more properties at risk in Suffolk, a 79.5% gap. Long Island also had two of the top 10 communities with the highest percentage of homes at risk — Fire Island (No.2 at 68%) and Long Beach (No.9, 47%).
And the future looks even stormier. Long Island claimed nine of the 10 communities facing the highest increases in risk by 2050 — with Merrick (172%) in the top spot, followed by Baldwin. Harbor, Inwood (in Manhattan), East Rockaway, Oceanside, Long Beach, Bellmore, Woodmere, Sag Harbor and Massapequa (75%).
It’s not just coastal communities threatened by sea level rise that are confronting increasing risks. Upstate and inland communities face river and lake flooding from intensifying rains.
First Street’s data can be found on FloodFactor.com, a website that allows users to search for their own homes and neighborhoods, and Realtor.com plans to include the data soon on its own website. The visual representation is jarring, with large swaths of deep red indicating the highest risk along many parts of the South Shore.
While any data set like this has uncertainty built into it — First Street’s model, for example, does not include any mitigation efforts undertaken in the future like sea walls — the information should be valuable to homeowners thinking about retreating from the coast, and municipalities mulling zoning codes and sinking tax revenues from lower property values.