October 17, 2018 Sea level rise observed since 1970 responsible for 43% of homes impacted by Hurricane Irma s storm surge

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1 October 17, 2018 Sea level rise observed since responsible for 43% of homes impacted by s storm surge (NEW YORK, N.Y.) Data scientists from the non-profit First Street Foundation in collaboration with Dr. Jeremy Porter, a professor at Columbia University, have found that sea level rise since caused an additional 57,000 homes to be impacted by s storm surge. With Hurricane Michael s devastating impact along Florida s panhandle still being quantified, First Street Foundation wanted to understand the role sea level rise played in similar, more documented events like Hurricane Irma. In, s storm surge impacted over 133,000 homes across Florida, causing extensive flooding and damage. The research used a geospatial analysis to model the impact of an Irma-like storm at the sea levels observed in, and found that ~57,000 of the properties impacted last year would not have been affected with sea levels signaling that the rise in sea level was responsible for these additional impacts. The study also found that if were to hit at the sea level projected for by the Army Corps of Engineers, approximately 15 inches above current levels, the storm surge would affect an additional 200,000 homes. In other words, a 1.26 foot increase in nearby sea levels alone would result in a 150% increase in the number of homes impacted by s storm surge. Similarly to what was found with our analysis of Hurricane Florence in the Carolinas, we know that sea level rise made the damage from significantly worse, said First Street Foundation s Head of Data Science Steven McAlpine. According to tidal data in the region, relative sea level off the coast of Florida has risen approximately 7 inches since. Higher sea levels cause greater storm surge, as there is more water available for hurricanes to push onto land, and that additional water removes friction that would otherwise slow the surge. Research has shown that sea level rise has a non-linear positive impact on storm surge; the conservative models used in this research show that increases in sea level rise result in an additional 23% relative increase in storm surge. Small increases in sea levels are causing disproportionate increases to the reach of storm surge. said Dr. Jeremy Porter, This is especially true in Florida because of the low-lying topography. In addition to sea level rise, the scientists found that changes in housing development patterns also played a significant role in the number of homes affected by s storm surge. Since the s, much of the region s wetlands and conserved areas have been developed for urban use. Many of the homes built in these areas were impacted by s storm surge. By applying s observed storm surge to the housing development patterns of, the scientists found that only 72,000 homes would have been impacted, compared to the 133,000 impacted in. In other words, 61,000 homes in the impacted surge area were developed since. Recent hurricanes such as, Florence and now Michael, are demonstrating how sea level rise has a dramatic impact on the number of homes affected by hurricane storm surge. As sea levels and coastal development continue to rise, this will only get worse, said Matthew Eby, Executive Director of First Street Foundation. The time to rethink America s sea level rise and adaptation strategy is now. First Street Foundation is a 501(c)(3) tech nonprofit that educates policymakers and the public about the risks, causes, and solutions to sea level rise. Methodology behind this research can be found here. For questions please reach out to pr@firststreet.org.

2 s Total Storm Surge Impact: Miami, Marco Island, and Key West : : : 76, , ,000 Residential development numbers held constant for all three scenarios Analysis Example: s Impact on Miami sea level Modeled storm surge: 3.1 ft Observed storm surge: 3.9 ft Sea level increase: +1.8 ft Modeled storm surge: 5.4 ft Miami location "% s combined:,, and Miami, FL

3 Analysis Example: s Impact on Marco Island sea level Modeled storm surge: 5.8 ft Observed storm surge: 6.5 ft Sea level increase: +1.8 ft Modeled storm surge: 8 ft Marco Island Location s combined:,, and Marco Island, FL "%

4 Analysis Example: s Impact on Key West sea level Modeled storm surge: 2.2 ft Observed storm surge: 2.9 ft Sea level increase: +1.8 ft Modeled storm surge: 4.5 ft Key West Location s combined:,, and Key West, FL "%

5 Top 15 Impacted County Housing Units Impacted by Irma / Irma-like storm Surge Level Surge Level Surge Level Miami-Dade 19,000 45, ,000 Monroe 20,000 24,000 27,000 St. Johns 4,000 7,000 23,000 Lee 2,000 6,000 21,000 Volusia 6,000 9,000 17,000 Broward 1,000 3,000 17,000 Collier 3,000 7,000 17,000 Charlotte 2,000 4,000 15,000 Duval 8,000 10,000 15,000 Brevard 3,000 5,000 14,000 Flagler 3,000 3,000 6,000 Clay 2,000 2,000 4,000 Sarasota 0 1,000 4,000 Putnam 1,000 1,000 2,000 Nassau 1,000 1,000 2,000 Values rounded to nearest 1000