The San Francisco Bay Area will bear the brunt of a predicted sea-level rise of 3 to 4 1/2 feet by the end of the century, a new report warns.
A sea-level rise coupled with a major storm could flood 270,000 Bay Area residents and cause nearly $100 billion (in year-2000 dollars) in property damage statewide, according to a report released Wednesday by the Oakland-based Pacific Institute research group.
San Mateo County would be the hardest hit of any coastal county, with an estimated $26 billion in damage from both bay and ocean flooding, compared to $7.8 billion for Santa Clara County with only bay flooding and $5.1 billion for San Francisco, with generally steeper shorelines other than the Marina area.
The next highest hit area would be Orange County, with $17 billion estimated damage, the report's damage maps indicate.
Bay Area "infrastructure" damage could include flooding both the San Francisco and Oakland international airports and many low-lying regions. Bay Area office or manufacturing areas, 22 sewage-treatment plants, 14 power plants, smaller airports (such as Palo Alto's) and other facilities could also be impacted.
The report, entitled "The Impacts of Sea-Level Rise on the California Coast," was commissioned by the California Department of Transportation, the California Energy Commission's Public Interest Research Program and the Ocean Protection Council.
The report's five co-authors -- Pacific Institute's Matt Heberger, Heather Cooley, Pablo Herrera, Peter Gleick and Eli Moore -- embody fields of expertise that include environmental engineering, energy and resource research, geography and environmental justice.
The report estimated the effects of a sea-level rise of between 1 and 1.4 meters (3.28 to 4.59 feet) as predicted by the end of the century due to global climate change.
Nearly two-thirds of the "at risk" property and infrastructure is in the Bay Area, according to the study.
Minority populations are those most at risk, statistically, the study warned.
Earlier elevation-based studies predict that up to a third of Palo Alto is subject to tidal/storm flooding up to several feet deep, primarily in the low-lying southeast quadrant. Hundreds of homes in East Palo Alto are exposed to potentially lethal deep flooding of 8 to 12 feet.
The new study estimated the impact of a "100-year flood" -- a flood with a 1 percent chance of occurring in any given year. Statewide, nearly a half million residents would be impacted by a sea-level rise of just 1 meter, either directly or by increased erosion of the coastline, the study predicts.
The mean sea level has risen nearly eight inches at the Golden Gate Bridge in San Francisco in the past century, and is projected to rise between 1 to 1.4 meters (3.28 to 4.59 feet) by 2100, according to the National Oceanic and Atmospheric Administration.
Heberger said changes needed generally fall into two categories.
He said in some instances settlements and infrastructure can be protected through "coastal armoring" with dikes, dunes, seawalls and bulkheads, which could cost at least $14 billion.
But in other cases it might be necessary to "retreat and allow the natural processes to occur.
"We're living with risk right now, and the report just said that the risk is going to increase," he said.
Co-author Moore cited studies of damage to Louisiana coastal communities following Hurricane Katrina as the basis of projections for many areas of the California coastline that are geographically similar to Louisiana's coast.
If present demographic and cultural patterns remain, Moore estimates that more than 15,000 affected households would not have access to a vehicle, a factor officials say led to the Katrina-related deaths of more than 1,400 people.
There would be 14,000 households with language barriers that could prevent the family members from understanding emergency-preparedness instructions or information, he estimated.
"California needs to learn from those mistakes, and the changes made need to be equitable and proactive in safeguarding all Californians," Moore said.
The report concludes that 41 square miles of coastline may be lost to erosion by 2100, affecting the homes of an additional 14,000 people.
The report, which includes detailed maps of populations and critical infrastructure at risk from flooding, is available online at http://www.pacinst.org/reports/sea_level_rise.