If global warming continues unchecked through 2100, rising sea levels will displace 480,000 Californians, put nearly $100 billion of property at risk of flooding, and erode away stone formations at Big Sur and other coastal bluffs, according to a new report from the Pacific Institute, a California environmental non-profit.

Even Disneyland could end up underwater if ocean levels rose 4.6 feet (1.4 m), the middle-of-the-road scenario envisioned by the study’s authors. That figure, taken from research by the Scripps Institute of Oceanography, is much higher than past estimates because it considers both thermal expansion (water expanding as it warms) and melting ice caps.

The government of California commissioned the study, The Impacts of Sea-Level Rise on the California Coast, to help it plan responses to climate change; even if greenhouse gas emissions stopped today, some sea-level rise is still inevitable.

A few of the more interesting findings:

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  • Rising oceans would sharply increase the risk of flooding at 140 schools, 29 sewage treatment plants, 30 power plants, and 3,500 miles of roads and highways. Also threatened would be the Long Beach Harbor in Los Angeles, home to the nations second-busiest port.
  • Of the $100 billion of property at risk, two-thirds sits on San Francisco Bay, with its 1,000-mile-long shore. The majority of this property is residential.
  • A rising ocean would also destroy high cliffs such as Big Surs through accelerated erosion.
  • The changes would have a disproportionate effect on low-income households and minorities.

“We saw it with Hurricane Katrina,” report co-author Eli Moore said in a news release. “Pre-existing social and environmental inequities make some communities less able to afford emergency preparedness materials, buy insurance policies, and evacuate to escape a disasters harm.”

The study suggests the flood risk could be minimized by improving defenses along 1,100 miles of coastline. Those should include new sea walls, levees, dunes, and offshore breakwaters, according to the authors. Such a plan would cost at least $14 billion plus $1.4 billion a year in maintenance costs. And miles of natural beaches would also be washed away if sea walls were built.

“California is leading the effort to offset the possible ravages of climate change and sea-level rise, but if we fail to respond, the consequences will be severe,” said Pacific Institute President Peter Gleick.

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