‘We Cannot Wait Much Longer’: King Tides Foreshadow a Far Wetter Future for SF Shoreline

Every time waves from king tides crash against San Francisco’s hard city edge like they did Friday, officials brace for flooding along the Embarcadero southeast of the Ferry Building. It’s a reminder that as baseline sea levels continue to rise, future floodwaters could inundate a vital part of the city’s transportation infrastructure: commuter rail lines.

The city is working on two solutions to cure its bayside flooding woes. The first is a shorter-term plan to raise the shoreline and use deployable temporary infrastructure (PDF) to block water from getting into the train system. The second would take decades: rebuilding a vulnerable stretch of San Francisco’s seawall and raising structures like the Ferry Building.

Elaine Forbes, executive director of the Port of San Francisco, said king tides have worsened over the past decade. That makes the flood-resiliency work especially urgent.

“We are seeing the impacts of climate change now,” Forbes said. “We have an immediate flood problem that we have to take care of now. We’ve been lucky, but we cannot wait much longer. Time is not on our side.”

Today, king tides — caused by a stronger-than-normal gravitational pull when the sun, moon and Earth align — mainly cause short-term nuisance flooding. However, they foreshadow a far wetter future for the city on the bay because of sea level rise caused by human-caused climate change.

“King tides are a very helpful visual representation of what our shoreline is likely to look like every single day in the not very distant future,” said Annie Kohut Frankel, manager of the California King Tides Project at the California Coastal Commission. “They are a warning more than a problem yet, but hopefully, we will listen to that warning.”

On Friday, that warning came in the form of bay water gushing onto the sidewalk on the Embarcadero, forcing people to walk around the waves. The king tides reached around 7.36 feet in San Francisco, according to the commission, which encourages people to capture and submit photos of flooding this weekend. But Forbes noted that seas are projected to rise several feet by the end of the century.

That means every time a king tide occurs in the not-so-distant future, the impact on the city will be compounded. Plus, Forbes said the flooding could be even worse if tides occur during a flood-inducing atmospheric river or a smaller storm like the one bearing down on Northern California this weekend with heavy rain, strong wind and high surf.

“A king tide gives us an idea of what is coming in the future,” she said. “Right now, it’s infrequent flooding, but it will become intermittent to frequent flooding over time.”

Since the 1880s, the Pacific Ocean has risen by about 8 inches along the West Coast, but state scientists predict more than a foot of bay rise by 2050 and more than 6 feet by the end of the century in the worst-case scenario.

Forbes is particularly worried about the area that floods today. To the naked eye, this area several hundred feet southeast of the Ferry Building looks like a pedestrian path and road next to the bay. But underneath the paved ground is a Muni portal, where trains enter the underground system, including BART.

This area is the most at-risk segment of the city’s seawall for future sea level rise. As seas rise and storms intensify, the promenade and railing could fail, and flooding could cause regular road shutdowns and damage the train system.

“The water would overtop and move right in and over into those tracks and down into the system,” Forbes said.

UC Berkeley professor Kristina Hill, a leading sea level rise scientist, said San Francisco’s current seawall is “a joke” because it was built quickly out of rubble, rocks, posts and concrete during the gold rush era.

“It is kind of an unusually fragile seawall for a city of this size,” she said. “There are even ships that were scuttled in it.”

The long-term fix from the port and the U.S. Army Corps of Engineers aims to reinvent 7.5 miles of the bayside shoreline at a cost of more than $13 billion. The draft plan for the San Francisco Waterfront Flood Study, released last year by the port, includes rebuilding the seawall — which would help stop water from harming the train system — and raising structures. The final report is tentatively set for public release in early 2026.

In the meantime, the Downtown Coastal Resilience Project could potentially raise the shoreline and put in new protective railings and deployable structures to block water at a cost of more than $250 million.

Next year, the port will select a consultant to complete the concept and detailed design. Forbes said construction could start as soon as 2028, and exact renderings of what the solution could look like are yet to be created.

“If we do not tackle it early, we will have serious impacts on our transit systems, and that is not something we can allow,” Forbes said. “It’s critical to get the improvements in soon. We can’t wait for the big dig and allow this intermittent flooding to continue to be a risk to the city.”