These U.S. Cities Are Most Vulnerable to Major Coastal Flooding and Sea Level Rise

Research Report by Climate Central

In late October 2012, Hurricane Sandy took a sharp left turn into the coasts of New Jersey and New York, leading to 157 deaths, 51 square miles of flooding in New York City alone, and an estimated $50+ billion in damage (Bloomberg 2013; Kemp and Horton 2013). The name “Sandy” was retired, but risks to coastal cities for Sandy-like flooding remain. On the five-year anniversary of the storm, Climate Central has ranked the U.S. cities most vulnerable to major coastal floods using three different metrics:

1. The total population within the FEMA 100-year floodplain
2. The total population within the FEMA 100-year floodplain as augmented by sea level rise projections for the year 2050
3. The total high social vulnerability population within the same areas as group #2

Each analysis examined coastal cities with overall populations greater than 20,000. For the first one, we tabulated “at risk” population by overlaying 2010 Census block population counts against FEMA’s 100-year coastal floodplains (Crowell et al 2013) using methods adapted from Strauss et al (2012). FEMA 100-year coastal floodplains factor in storm surge, tides, and waves, and include all areas determined to have an at least one percent annual chance of flooding. Based on locations meeting these criteria and population density, New York City ranked first, with over 245,000 people at risk, followed by Miami and then Pembroke Pines, also in South Florida.

In our second analysis, we re-ranked cities based on which have the largest populations in the expanded areas that could be threatened in the year 2050 — due to sea level rise driven by climate change, plus nonclimatic factors such as local land subsidence. We determined these areas by using median local sea level rise projections for midcentury (Kopp et al 2014) under an unrestricted emissions scenario (“Representative Concentration Pathway 8.5”) to additively elevate the FEMA 100-year floodplain, and accordingly extend it as topography allows, following methods detailed in States at Risk: America’s Preparedness Report Card Technical Methodology. After this adjustment, New York City still had the greatest number of people on threatened land, followed by Hialeah, Florida and Miami. 36 cities in Florida placed in the top 50.

The top five cities with the greatest increase in population on land at risk when adding on sea level projections were New York City, with a difference exceeding 181,000, plus Hialeah, Boston, Fort Lauderdale, and The Hammocks, Florida.

The yellow, orange and red show areas at or below Sandy’s peak flood elevation at The Battery.

Finally, we also ranked coastal cities by their “high social vulnerability” population within the areas delineated by our second analysis. High social vulnerability was determined using the Social Vulnerability Index developed by the Hazards and Vulnerability Research Institute, which incorporates 29 different socioeconomic variables to evaluate the ability of communities to prepare and respond to environmental hazards such as floods. New York City, Philadelphia, Houston, Baltimore, and Miami were ranked as the top five cities with the largest high social vulnerability populations within the future FEMA 100-year floodplain — and thus face a difficult double jeopardy over time.

Sea level rise is a key indicator and consequence of climate change.

To learn more about coastal cities at risk visit Climate Central’s States at Risk and Risk Finder.

Analysis by Scott Kulp, PhD and Benjamin Strauss, PhD. Dyonishia Nieves, Shari Bell, and Dan Rizza contributed to this report


Bloomberg, Michael. 2013. “A stronger, more resilient New York.” City of New York, PlaNYC Report.

Crowell, Mark, Jonathan Westcott, Susan Phelps, Tucker Mahoney, Kevin Coulton, and Doug Bellomo. 2013. “Estimating the United States Population at Risk from Coastal Flood-Related Hazards.” In Coastal Hazards, edited by Charles W Finkl, 245–66. Springer. doi:10.1007/978-94-007-5234-4.

Kemp, Andrew C., and Benjamin P. Horton. 2013. “Contribution of relative sea‐level rise to historical hurricane flooding in New York City.” Journal of Quaternary Science 28.6: 537-541.

Kopp, Robert E., Radley M. Horton, Christopher M. Little, Jerry X. Mitrovica, Michael Oppenheimer, D. J. Rasmussen, Benjamin H. Strauss, and Claudia Tebaldi. 2014. “Probabilistic 21st and 22nd Century Sea-Level Projections at a Global Network of Tide-Gauge Sites.” Earth’s Future 2 (8): 383–406. doi:10.1002/2014EF000239.

Strauss, Benjamin H, Remik Ziemlinski, Jeremy L Weiss, and Jonathan T Overpeck. 2012. “Tidally Adjusted Estimates of Topographic Vulnerability to Sea Level Rise and Flooding for the Contiguous United States.” Environmental Research Letters 7 (1). IOP Publishing: 014033. doi:10.1088/1748-9326/7/1/014033.

Alaska Towns At Risk from Rising Seas Sound Alarm

By Oliver Milman, The Guardian

The U.S. government’s withdrawal from dealing with, or even acknowledging, climate change may have provoked widespread opprobrium, but for Alaskan communitie…

These Are the Crazy Climate Records from 2016 You Haven’t Heard Much About

By now, we’ve all heard that 2016 was the hottest year on record, and that heat-trapping greenhouse gases hit their highest concentration ever, surpassing 400 parts per million for the first time in nearly 1 million years.

Global surface temperature in 2016 compared to the 1981-2010 average.
Click image to enlarge. Credit: NOAA

But there are other climate change-related records that have flown more under the radar. Several of those records were highlighted Thursday in the annual State of the Climate report, released in the Bulletin of the American Meteorological Society:

For example, during August, ice-free areas of the Barents Sea (north of Norway and Russia) were up to 20°F (11°C) above average, a figure that stunned climate scientists.


The Chukchi Sea off Alaska and the waters to the west of Greenland were 13°F to 14°F above average. Those warm waters were linked to the smallest annual winter peak in sea ice levels and the second lowest annual minimum.

The average land surface temperature for the Arctic was 3.6°F (2.0°C) above the 1981-2010 average — a 6.3°F (3.5°C) rise in temperatures since 1900. Record-high temperatures were measured below the surface of the permafrost, or permanently frozen ground, across the North Slope of Alaska.

Glacier mass balance — the difference between ice lost through melting and ice gained through new snowfall — each year since 1980 (blue bars) for the 44 glaciers in the World Glacier Monitoring Service’s reference network. The orange lines shows the running total ice mass loss between 1980–2015. These glaciers have lost the equivalent of cutting a 70-foot thick slice off the top of the average glacier.
Click image to enlarge. Credit: NOAA

“2016 was a year in the Arctic like we’ve never seen before,” Jeremy Mathis, director of the National Oceanic and Atmospheric Administration’s Arctic research program and an author of the report, said.

The rate of warming in the Arctic, which is happening at twice the rate of the rest of the globe, has major impacts on local ecosystems, but also further drives the warming of the planet, as the sea ice that would reflect the sun’s rays back to space is lost.

And for the 37th consecutive year, alpine glaciers retreated across the globe. These glaciers are a major source of water for local communities, and their loss has led to concerns about water security, particularly in places like Southeast Asia.

Global surface temperature in 2016 compared to the 1981-2010 average.
Click image to enlarge. Credit: NOAA

Global sea level was also the highest on record — and sea surface temperatures globally were also record-high — with a sea level 3.25 inches higher than they were in 1993, the beginning of the record. The year marked six consecutive years of global sea levels being higher than the year before. Over the long term, sea level rise is driven by the warming of the oceans (as water expands as it heats up) and the addition of water from melting polar ice.

On a more local level, the year, which was the second hottest on record for the U.S., was the 20th consecutive warmer-than-normal year for the country — a mark of the impact that long-term warming is having.


2016: Warmest Year on Record

CO2 Above 400 ppm: First Time in 800,000 Years Online — The 27th annual State of the Climate report has confirmed that 2016 topped 2015 as the warmest year in 137 years of record keeping.