The ocean is rising. What will happen to San Francisco?

Written by Monica Villavicencio
Melting glaciers and a warming climate will raise ocean levels between one and three feet by the end of the century, scientists predict.Will San Franciscans be left scrambling for cover? USF’s John Callaway explores what higher oceans would mean for life in the City by the Bay.

John Callaway, professor, environmental science/management: Studies wetland restoration and the impact of climate change on wetlands. The National Science Foundation and U.S. Environmental Protection Agency fund his work.professor, environmental science/management: Studies wetland restoration and the impact of climate change on wetlands. The National Science Foundation and U.S. Environmental Protection Agency fund his work.

If sea levels rise as predicted, what will flood?
Hundreds of thousands of houses, roads, and hospitals around the edge of the Bay would be affected. San Francisco and Oakland airports, the ports, the Great Highway along the edge of Ocean Beach, and the city’s sewage treatment plant would all likely flood. Foster City and Treasure Island are also very close to sea level.

Unfortunately, sea-level rise would have a disproportionate impact on low-income communities. Those communities tend to develop on land closer to sea level because, except for property directly on the water, it’s often cheaper.

Can we build walls to keep the water out?
Certainly, a large part of the response will be engineering solutions. Many areas already have levees and sea walls to protect them from flooding, and there will likely be additional sea walls and levees to protect the really high-value areas, such as downtown San Francisco. But the cost will be substantial.

What we really need to think about is a longer-term solution, like a “managed retreat”—the use of the lowest areas adjacent to the coast for farming or other things that are easily relocated, rather than for high-value development. Then, as sea level rises, we can move back.

ocean

Scientists warn that the Bay Area’s wetlands could be wiped out by the end of the century, possibly sooner. Why does this matter?
The wetlands around the Bay protect us from the effects of storms and remove contaminants from water. Think of them as sponges, absorbing water so it doesn’t flood adjacent areas. The concern is that as we close in on really high sea-level estimates, many wetlands will slowly start to lose elevation. Plants will die out, and we’ll lose many of the benefits that those healthy ecosystems provide. Unfortunately, about 95 percent of Bay Area wetlands have already been lost due to agricultural, urban, and suburban development.

Any good news?
Luckily, over the last few decades there’s been a big push to restore the Bay’s wetlands. If all the salt pond areas currently slated for restoration are converted back to tidal marsh, we would more than double the acreage of wetlands within the South Bay, thus more than doubling the benefits those wetlands provide.

 

 

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