Surging Seas Sea level rise analysis by Climate Central

Louisiana and the Surging Sea

Description: A vulnerability assessment with projections for sea level rise and coastal flood risk.
Date: August 2015

Full PDF of Report

Executive Summary

Low-end sea level projections lead to a greater than even chance of record-breaking floods exceeding 6 feet above the high tide line by 2040 at Grand Isle, Louisiana, on the sinking Mississippi Delta; ranging to 2070 at Sabine Pass North, just across the border in Texas. Statewide in Louisiana, more than one million people live below 6 feet, including roughly a quarter million that appear to lack levee protection, using the methodology of this report. A disproportionate fraction of this group has high social vulnerability, meaning limited resources to prepare for, respond to or recover from natural disasters. Under high-range sea level projections, there is a greater than 3 in 4 chance of floods exceeding 10 feet this century, exposing nearly half a million total population after accounting for levees. Higher floods are possible, with lower probability. 

In Louisiana, some $7.8 billion in property value plus more than 236,000 people living in more than 101,000 homes sit on 5,631 square miles of land less than 6 feet above the local high tide line, and apparently not protected by levees. The exposure of population with high social vulnerability, 65,574, is disproportionately high, 40% greater than would be expected by chance alone. Of the exposed high vulnerability population, one quarter lives in one zip code (70363 in Houma), while more than half live within just four. Exposure of population and property increases fivefold when not accounting for levees, including more than 1.1 million in total population.

Compared to 6 feet, significantly more total property, population, and housing sit on land below 10 feet: $14 billion and nearly 455,000 people living in more than 189,000 homes across 6,791 square miles, accounting for levees.

Nonresidential buildings and infrastructure are widely at risk as well. All told, and still accounting for levees, 4,390 miles of road lie on land below 6 feet in the state; 5 hospitals; 21 libraries; 76 schools; 202 houses of worship; and 2,084 EPA-listed sites, screened to include mostly hazardous waste sites, facilities with significant hazardous materials, and wastewater generators. At 10 feet, these numbers amount to 7,809 miles of road, 15 hospitals, 31 libraries, 185 schools, 415 houses of worship, and 3,562 EPA-listed sites. 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 mult

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 http://sealevel.climatecentral.org/ssrf/louisiana.

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.