An Earthquake in Japan Speaks to a Sea Wall in San Francisco

The Port of San Francisco (which manages 12 miles of the city’s waterfront, including the three miles that are supported by the seawall) had assumed the wall needed to be replaced, but it didn’t know how urgent until 2016 when officials did one preliminary study published the seismic vulnerabilities. Unlike some levees, San Francisco offers structural support as well as flood protection. The following 2020 report details its weaknesses on both fronts. As climate change raises sea levels, the dike will increasingly have to function in a context for which it was not designed. Since an earthquake could happen any day, the port has an immediate priority to ensure the integrity of the dike in such an event. However, the rise in sea level and its uncertainties as to how fast and how high must also be taken into account. Decisions now made to reduce risk must take into account the unrecognizable.

Patrick King, who heads port and maritime work at Jacobs, the engineering office that manages the port’s resilience program, formulates the urgent challenge of designing a future waterfront. “This infrastructure was built for a specific environment that no longer exists and is rapidly changing,” he said. And now we have to predict to the best of our knowledge what this environment will look like.

“Wall” is a generous word for the pile of stones lying on the mud that runs along the northeastern waterfront in San Francisco. During the feverish early days of the gold rush, the San Franciscans built the levee in a sloppy attempt to create some flat land on the edge of the hilly city. Horses struggled to haul carts filled with gold over the hills, and the San Franciscans needed warehouses and counting houses on level ground. Impatient for steam-powered shovels arriving from across the country, residents began dumping whatever was there into the marshland of Yerba Buena Cove: loose sand, remains of city construction, unwanted goods, trash, remains of abandoned ships. After a year, San Francisco had expanded three blocks into the bay.

To curb the building chaos, the California legislature has set up a Board of State Harbor Commissioners to draw up a port development plan. Construction of their first seawall – essentially a rescue mission for the ruined port – began in 1867. A better-funded effort began in 1878, and construction continued in stages over the next four decades.

Although longevity was not a priority, the wall still stands – long outlasts what everyone could expect. And that is worrying for some experts.

“I would suggest that San Francisco is triple at risk,” King said: earthquakes, sea level rise, and obsolete infrastructure.

So far the wall has mostly worked, if hardly at all. During the earthquake of 1906, the sea wall shifted into the bay, tram tracks broke, pipes broke and houses were destroyed. Entire stretches of road slid sideways; other parts fell a few meters. In today’s city, a similar disaster would be even worse.