California, Oregon, Washington and the Surging Sea
Description: A vulnerability assessment with projections for sea level rise and coastal flood risk.
Date: June 2014
Executive Summary
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 flood statistics with local sea level rise projections developed by the U.S. National Research Council. Under mid-range projections, floods exceeding today’s historic records are likely to take place throughout California, Oregon and Washington within the next 30 years. In Southern California, such floods would become annual events within the same period; in Northern California and Puget Sound, this would take up to six decades.
Low-range sea level projections lead to an at least 50 percent chance of floods exceeding 3 feet above the high tide line within 50 years, at all sites assessed from San Diego to Seattle. Under high-range projections, there is an at least 50 percent chance of floods above 6 feet at each site by the end of the century, with much higher floods possible but with lower probability.
1,300 square miles of land lie less than 3 feet above the high tide line in California, Oregon and Washington. The total drops to 475 when accounting for potential protections from levees, beach ridges and other features. Some $42 billion in property value, and 72,000 homes, sit on this smaller area. These figures jump to $111 billion and 202,000 homes on 825 square miles of land under 6 feet, after accounting for potential protections.
Also accounting for protections, California accounts for half of the total exposed land at each elevation, but more than 85 percent of exposed homes and property value. Washington accounts for about one third of the total land exposure, and one eighth of homes and property. While Oregon is home to almost one fifth of the exposed land at each elevation, its housing and property exposure range from 1 to 3 percent for the total region.
Combined, the three states have 1,047 miles of road below 3 feet, after accounting for potential protections, plus 32 schools, 7 power plants, and 569 EPA-listed sites such as hazardous waste dumps and sewage plants. At 6 feet, these numbers grow to more than 3,125 miles of road, 105 schools, 25 power plants, and 1,938 EPA-listed sites.
This report is being released as a summary of findings coincident with the online launch of a Surging Seas Risk Finder tool for each coastal state, accessible via http://sealevel.climatecentral.org
The tool includes:
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Interactive local projections of sea level rise and increasing coastal flood risk from 1-10 feet by decade;
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A zooming, zip-searchable map of low-lying areas threatened, plus layers showing social vulnerability, population density and property value;
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Detailed assessments of populations, property, infrastructure and contamination sources exposed, for each implicated county, city, town, zip code, planning district, legislative district and more; and
- State- and county-wide heat maps facilitating high-level vulnerability comparisons.
Detailed knowledge of vulnerability is a critical tool for communities seeking to build resiliency to the climate challenges of today and the future.