Surging Seas Sea level rise analysis by Climate Central

Pennsylvania and the Surging Sea

Description: A vulnerability assessment with projections for sea level rise and coastal flood risk.
Date: July 2016

Full PDF of Report

Executive Summary

In records running back to 1900, Philadelphia has never seen waterfront flooding that reaches 4 feet above the local high tide line. But under a mid-range sea level rise scenario, floods within the Delaware Estuary exceeding 4 feet are more likely than not to take place by 2040, less than one 30-year mortgage cycle away. Under a low-range scenario, chances are just below even; and under a high-range scenario, they reach 3 in 4. At the other end of the spectrum, under high-range projections, there is roughly a 4 in 5 chance of floods above 9 feet by the end of the century.

Nearly 9 square miles of land lie less than 4 feet above the high tide line in Pennsylvania. Some $686 million in property value, and more than 5,000 people residing in more than 2,000 homes – mostly in Philadelphia – sit on this area. More than $250 million of the property sits within just one zip code, 19153 (Philadelphia International Airport). Totals jump to some $3.4 billion, more than 27,000 people, and more than 12,000 homes on more than 29 square miles of land under 9 feet. The state has 63 miles of road below 4 feet, plus 23 hazardous waste sites, 15 wastewater sites, and 4 power plants. At 9 feet, these numbers grow to nearly 227 miles of road, 114 hazardous waste sites, 37 wastewater sites, and 10 power plants, as well as 2 museums.

Sea levels are rising at an accelerating rate, and the scientific community is confident that global warming is the most important cause. Higher sea levels translate to more and higher coastal floods. To forecast future risk, this analysis integrates historic local sea level trends and flood statistics with global sea level rise scenarios, developed by a multi-agency federal task force led by NOAA in support of the recent U.S. National Climate Assessment.

This report is being released as a high-level summary of findings and methods, coincident with the online launch of a Surging Seas Risk Finder tool for the state, providing much more detailed and localized findings, and accessible via

The tool includes: 

  • Interactive local projections of sea level rise and increasing coastal flood risk from 1-10 feet by decade;
  • A zooming, zip-searchable map of low-lying areas threatened, plus layers showing social vulnerability, population density and property value;
  • Detailed assessments of populations, property, infrastructure and contamination sources exposed, for each implicated county, city, town, zip code, planning district, legislative district and more;
  • State- and county-wide heat maps facilitating high-level vulnerability comparisons; and
  • Brief customized “fast look” reports that integrate key findings from across all analyses for each locality, and provide interpretation and context.

Detailed knowledge of vulnerability is a critical tool for communities seeking to build resiliency to the climate challenges of today and the future.