May 26, 2016

Bay Area’s future depends on managing rising sea levels

San Francisco, CA
USA
by
John King
,
The San Francisco Chronicle
While San Francisco, seen here from Treasure Island, is less vulnerable to rising sea levels than other parts of the Bay Area, portions of areas bordering the bay would be at risk. Photo: Michael Macor, The Chronicle
While San Francisco, seen here from Treasure Island, is less vulnerable to rising sea levels than other parts of the Bay Area, portions of areas bordering the bay would be at risk. Photo: Michael Macor, The Chronicle

San Francisco has the longest unbroken tide record in the Western Hemisphere, dating back to June 30, 1854. Since 1900, tide gauge measurements indicate sea levels have risen at a rate of 1.94 millimeters a year, or 7.6 inches per century. This rate of sea level rise in the 20th century is unprecedented in at least the past two millennia.[1] California's central coast is especially vulnerable to sea level, and coastal erosion is already a serious problem in many communities.

 

An abundance of scientific studies says the bay’s average tide could climb several feet or more by 2100, with most change coming in the decades after 2050. It’s an inexorable shift that threatens low-lying neighborhoods as well as the fish, birds and wildlife that need tidal flats to survive.

  • If sea levels were to rise 36 inches, the midrange increase through 2100 projected in the most recent study by the National Research Council, water would wash into San Francisco’s Ferry Building twice daily at high tide.
  • With just 16 inches of sea-level rise, the tollbooths of the Bay Bridge could be flooded during storms.
  • $35 billion worth of public property in San Francisco is at risk if sea-level rise by 2100 reaches 66 inches, the upper level forecast by the National Research Council.
  • Already, lanes on the ramps connecting Highway 101 to the Shoreline Highway near Mill Valley are closed regularly — 30 times in 2015 — because of high tides, a small but vivid hint of how profoundly our region will be altered in coming decades unless the Bay Area starts making plans now.