Sea level rise responsible for 20% of the homes impacted by Hurricane Florence’s storm surge

FirstStreet.org

September 24, 2018

(NEW YORK, N.Y.) Data scientists from the non-profit First Street Foundation have found that sea level rise since 1970 caused Hurricane Florence’s storm surge to significantly affect more than 11,000 homes.

Hurricane Florence’s storm surge impacted over 51,000 homes by pushing water over 25% or more of each property. First Street’s research used a geospatial analysis to model this storm surge at the sea levels observed in 1970, and found that because of higher sea levels, over 11,000 of those impacted properties would not have been affected in 1970 – signaling that sea level rise is responsible for these additional impacts. The study also found that at the sea level projected for 2050 by the Army Corps of Engineers, approximately 15 inches above current levels, the same storm surge from Hurricane Florence would approximately double the impact and affect 102,000 homes.

“Even though the impact of Hurricane Florence continues to be felt, we already know that sea level rise has made the damage significantly worse, as observed with other recent storms,” 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 the Carolinas has risen approximately 6 inches since 1970. 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.

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 Hurricane Florence’s storm surge. Since the 1970’s, much of the region’s wetlands, farms, and conserved areas have been developed for urban use. Many of the homes built in these areas were impacted by Hurricane Florence’s storm surge. By applying Hurricane Florence’s observed storm surge to the housing development patterns of 1970, the scientists found that only 23,000 homes would have been impacted, compared to the 51,000 impacted today.

“With sea levels and coastal development on the rise, the impacts of hurricane storm surge 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.

FirstStreet.org

Sea Level Rise Worsens Storm Surge

1970Hurricane Florence Scenario

Wrightville Beach Location

2018Hurricane Florence

2050 Hurricane Florence Scenario

Hurricane Florence Scenarios combined: 1970, 2018, and 2050

1970 sea levelModeled storm surge: +6.0 ft1

Sea level increase: +0.5 ftObserved storm surge: +6.6 ft1

Sea level increase: +1.7 ftModeled storm surge: +8.2 ft1

Analysis Example: Hurricane Florence’s Impact on Wrightsville Beach, NC

1970: Hurricane Florence Scenario

2018:Hurricane Florence

2050: Hurricane Florence Scenario

Hurricane Florence’s Total Storm Surge Impact: North and South Carolina, Virginia

102,000HOMES

51,000HOMES

40,000HOMES

Wilmington, NC

Wrightville Beach, NC

1 Florence max surge numbers at Wrightsville, NC USGS station 02093222 in NAVD88

Residential development numbers held constant for all three scenarios

1970

2018

2050