Sea Level Rise a Major Threat to San Francisco

New projections predict a possible 7-foot rise in sea levels.

Sea levels on the California coast could rise as much as seven feet by 2100 and put tens of thousands of vulnerable San Franciscans at risk of daily flooding, according to a new report from the California State Legislative Analyst’s office. Combined with the impact of increasingly massive fires throughout the state, the projection makes for a grim one-two punch for the Bay Area.

The Aug. 10 report, which summarizes the impact rising sea levels would have on California residents, businesses, and infrastructure, acknowledges that it is difficult to focus on mitigating the long-term impacts of climate change as officials scramble to respond to immediate challenges of the coronavirus pandemic. But the report urges state and local officials to treat sea level rise with a similar sense of urgency.

“The state and its coastal communities cannot afford to defer all preparation efforts until economic conditions have fully rebounded from the recent crisis,” the report states. “The magnitude of the risks described in this report highlight the importance of California including [sea level rise] preparation activities among its many pressing priorities.”

California sea levels are projected to rise half a foot by 2030 and up to seven feet in the next 80 years, although the report notes that weather events such as storm surges, exceptionally high “king tides,” and El Niño events could make the actual sea level rise greater. Rising sea levels will cause coastal flooding, erosion of coastal cliffs and beaches, and rising groundwater levels. 

Between $8 billion and $10 billion worth of existing property in California will likely be underwater by 2050, the report states, and an additional $6 billion to $10 billion will be at risk at high tide. A six-foot sea level rise, combined with recurring annual storms, would put over 480,000 California residents and $119 billion in property value. Five feet of sea level rise would put 55 percent of coastal habitats in California at high risk of flooding and damage. Rising sea levels could also contaminate drinking water with saltwater or toxic materials.

The report warns that the effects of rising sea levels would be serious and even catastrophic for the San Francisco Bay Area. A four-foot increase in sea levels would put a significant amount of Bay Area infrastructure at risk of flooding, including 59 miles of highways and bridges, 48 miles of freight rail lines, 20 miles of passenger rail lines, 11 acres of ferry terminals, 780 acres of seaports, and 4,670 acres of airports. A six-foot increase would put 30 San Francisco wastewater treatment plants at risk of flooding — far more plants than in any other part of the state — which could cause toxic sewage leaks that endanger the health of the surrounding community.

The effects of sea level rise would disproportionately affect vulnerable communities in San Francisco — such as those who are low-income, renters, not proficient in English, without access to a car, or disabled. In the event of a four-foot sea level rise, nearly 28,000 San Francisco residents classified as “socially vulnerable” would experience daily flooding.

In addition, over 104,000 existing jobs in the San Francisco Bay Area would be lost or forced to relocate in the event of four feet of flooding, including jobs at major tech companies.

The report urges state and local officials to take action despite the ongoing COVID-19 crisis and the financial constraints the pandemic imposes, and to begin coordinating and planning response strategies. The report points to the Bay Adapt regional strategy initiative launched by the San Francisco Bay Conservation and Development Commission as an example of a useful short-term response.

“Waiting too long to initiate adaptation efforts likely will make responding effectively more difficult and costly,” the report states. “Planning ahead means coastal adaptation actions can be strategic and phased, helps ‘buy time’ before more extreme responses are needed, provides opportunities to test approaches and learn what works best, and may make overall adaptation efforts more affordable and improve their odds for success. The next decade represents a crucial time period for taking action to prepare for [sea level rise].”

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