‘We can’t depend on the city’: Why was S.F. so unprepared for the recent storms?

“If I wasn’t there, it would have been bad,” Bradshaw said, standing in a drizzle at 17th and Folsom a few days after New Year’s Eve. “We can’t depend on the city, so as a business owner, I have to be more proactive.”

While the near-record rainfall that hit San Francisco was certainly a factor in the flooding, the city’s antiquated sewer system compounded the problem.

Now, after another round of punishing rains left San Francisco this week — causing at least $46 million in damages to homes, businesses and city-owned property from all the recent winter storms combined— the weather’s impact on the region has brought into sharp relief the challenge the city and its residents and business owners face with future storms.

The atmospheric river that lashed San Francisco on Dec. 31 far exceeded what city leaders said they’d expected, leading to an initially chaotic and uncoordinated response.

Storm drains backed up, wrecking businesses and homes across San Francisco. Storm drains backed up, leaving the city reliant on volunteers to clear them out. Officials didn’t deploy water barriers in the Mission that would have reduced flooding. And the city repeatedly ran out of sandbags, giving some residents no option but to fill bags themselves at the beach.

The composition of San Francisco’s sewer system — created for both sewage and rainwater — makes it uniquely vulnerable to flooding. But residents and legislators say officials have dragged their feet on making much-needed upgrades, despite long knowing that certain neighborhoods are prone to debilitating floods.

Instead, the city has largely relied on costly interim solutions like sandbags and flood barriers, raising the question of how the city will handle similar storms in the future.

The storm dumped 5.46 inches on San Francisco, making it the second-wettest day on record, federal weather forecasters said.

The city’s Department of Emergency Management said Wednesday in an initial estimate that the recent winter storms caused $25 million in damages to public and private property, and another $21 million in damage to city-owned property outside the county.

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San Francisco Department of Emergency Management Executive Director Mary Ellen Carroll said that while the city hadn’t been expecting the level of rain it received, she was proud of the city’s efforts during recent storms.

Still, she acknowledged that the storm also revealed the challenges the city now faces in the future, and “flooding is a natural consequence of climate change.”

In light of this month’s intense rain and winds, San Francisco leaders recently announced that small businesses in the city’s flood zone could seek compensation for up to $5,000 in damages. Small businesses outside the flood zone could get up to $2,000, with grants awarded on a first-come, first-served basis.

Officials are overseeing efforts to upgrade infrastructure in flood-prone areas like 17th and Folsom — projects totalling more than $600 million . The deadlines for these projects, which are still years away, came about after the San Francisco Bay Regional Water Quality Control Board threatened to file a lawsuit against the city in 2021.

Most of those projects are still years from completion.

Separately, the S.F. Public Utilities Commission is upgrading its aging system through a 20-year, multibillion-dollar project .

David Sedlak, a professor in the Department of Civil and Environmental Engineering at UC Berkeley, said it’s likely that major storms will become more common. Ultimately the infrastructure upgrades won’t do enough, he said, and it would be “prudent” for the city to explore other approaches to cut damage in the short term.

A fundamental question for city sewer engineers, Sedlak said, is what size storm should San Francisco’s system be designed to accommodate?

“Do you design it for a storm that comes every 50 years, 100 years, 150 years?” he said. “By definition, there has to be some size of storm that the public is unwilling to pay for.”

For storms beyond that capacity, “we will just have to deal with the effects of it.”

Those effects, though, are costly, and the city has moved to shield itself from being held liable for those costs.

The city has mapped areas prone to flooding and passed an ordinance requiring home sellers to alert buyers if properties are in those areas.

After the New Year’s Eve inundations, Jen Kwart, spokesperson for the City Attorney’s Office, said that “just because the city’s infrastructure is pushed beyond its capacity by an extreme weather event, that does not mean that the city is responsible for the damage that results from that weather event.”

At the same time, the city is relying on Band-Aid fixes such as flood barriers.

Used properly, barriers help reduce street flooding — but cost more than $5,600 to man over a 24-hour period. The city did not deploy the barriers until several days after the New Year’s Eve storm, leading to significant street flooding in the Mission that caused tens of thousands of dollars in damages.

The San Francisco PUC defended its decision not to erect the barriers before the Dec. 31 storm. Joseph Sweiss, a spokesperson for the commission, said in an email that the city uses forecasts to decide whether to set up the barriers, and the city had not expected to get as much rain as it did that day.

Overall, Sweiss said San Francisco’s combined sewer system worked as designed, and the Dec. 31 flooding was due to the storm’s “historic intensity and duration.” The 17th and Folsom area is particularly vulnerable to flooding, he said, because it used to be a navigable waterway, and is lower in elevation than everything around it.

Supervisor Hillary Ronen, who represents the Mission, said she thinks the city should have put up the flood barriers prior to the New Year’s Eve storm and she will work to make sure that happens consistently in the future.

But the most comprehensive fix to the Mission’s flooding problems, in her view, is prohibitively expensive.

“Basically the only option is to knock down all the buildings and build them to be flood resilient,” she said. “That’s an amount of money that’s really hard to do, and the displacement... it’s just a really, really difficult situation.”

The issues extend beyond the Mission. Not long after Marina Boulevard flooded during heavy rains in October 2021, Supervisor Catherine Stefani wrote to leaders of the PUC and the city’s Public Works department. Residents in the area reported that backed-up pipes had sent toilet paper and dead rodents into their homes, Stefani said.

Stefani, who represents the Marina neighborhood, asked if the flooding could be related to changes the city had made to its drainage infrastructure. The city had recently decommissioned a Pierce Street pipe that drained sewage into the bay.

The week after Stefani sent her letter, she got a response from the PUC’s general manager, Dennis Herrera. The storm had been 10 times larger than the city’s sewer system could handle, Herrera told her.

No city could design its sewers to accommodate that much rain, he said.

And Herrera said the Pierce Street pipe closure had nothing to do with the flooding on Marina Boulevard. An analysis by his staff had concluded that it would have happened even if the pipe was still in use, he told Stefani.

Sweiss, the PUC spokesperson, told The Chronicle that the agency stands by that letter and “the same conclusion would apply to the New Year’s Eve storm, which was an even bigger storm.”

As climate change wreaks havoc around the world, San Francisco is not alone in having to contend with this reality. Over the past several years, cities across the country have been buffeted by once-in-a-generation storms that have brought flooding, extreme temperatures, snow and other hazards.

Cities in the U.S. and elsewhere have had to take extreme measures to protect their coastlines or make other plans. Venice, Italy, constructed a $6 billion network of 78 yellow flood gates to protect the town from high tides.

A decade ago, Hurricane Sandy killed 44 people in New York City, damaged 20,000 homes, and caused other major impacts. The city last year unveiled a $52 billion proposal to build sea barriers across New York Harbor — protection from future storms.

And in Houston, a Gulf Coast city that often deals with torrential rains, three 500-year storms hit the region back-to-back-to-back from 2015-2017. They showed “climate change is the new status quo,” said Lara Cottingham, the city’s former chief sustainability officer. “The question is when, not if.”

Houston and other southeast Texas communities are working to build a massive “coastal spine” to protect the city’s vulnerable ship channel from a high wind-high surge storm that could potentially decimate the region’s petrochemical industry.

As cities begin building infrastructure to deal with climate change, they must also respond to the disasters happening in real time. In California, that means dealing with the recent atmospheric rivers that have already claimed at least 20 lives.

“They have to do both,” Cottingham said. “That’s what’s really hard for cities.”

Trisha Thadani, J.D. Morris and St. John Barned-Smith are San Francisco Chronicle staff writers. Email: tthadani@sfchronicle.com , jd.morris@sfchronicle.com, stjohn.smith@sfchronicle.com Twitter: @TrishaThadani @thejdmorris