SAN FRANCISCO — As Hurricane Irma bears down on Florida, local experts are warning that the the Bay Area is also at risk of inundation from fierce rainstorms, extreme high tides and steadily rising sea levels caused by climate change.
Noting that the 400-mile-long San Francisco Bay coastline is lined with crowded roads and a fragile infrastructure, a Wednesday panel sponsored by the prestigious National Academy of Sciences urged that Bay Area cities pull together to protect the region from future flooding.
The goal of the workshop was to seek engineering, environmental and social solutions to the urban challenges posed by a changing climate, even as the Trump White House denies that the problem is real.
“We have to make a circle with everybody inside of it — and work it out,” said Gary Griggs, a professor of Earth and planetary sciences at UC Santa Cruz. “All ice melts at 32 degrees. It doesn’t matter if you’re a Republican or a Democrat.”
The Bay Area’s economic health relies on a vast network of roads, power, wastewater treatment facilities and railroads — and the region’s cities’ disparate approaches could wreak regional havoc, Griggs and other experts agreed.
For example, if Berkeley does not build protective structures on its shoreline — but adjacent communities do — there could be major disruption of traffic all along the I-80 corridor, said Mark Stacey, professor of environmental engineering in UC Berkeley’s Department of Civil and Environmental Engineering.
“There is a regional cascade effect — triggering problems inland for people who might not care what Berkeley does with its water,” he said.
Counites should be aware of the vulnerabilities in other parts of the Bay Area, because it affects their traffic, said Stacey, who is conducting an analysis of widespread traffic and railroad disruptions triggered by localized flooding from San Francisco Bay.
“Santa Clara county traffic would be severely impacted if access to the Dumbarton or San Mateo Bridges was reduced or cutoff,” he said.
There are many other examples.
Livermore residents could be startled to discover that it’s harder to flush a toilet if a wastewater treatment plant — miles away, in Hayward — is suddenly flooded, said Larry Goldzband of the Bay Conservation Development Commission.
Businesses all over the Bay Area could suffer if the Port of Oakland is inundated, said former San Francisco supervisor Susan Leal of Urban Water Works, a consulting company which works with utilities to protect water reliability. Twice last year, shipping was interrupted at the port because of flooding, she said.
Flooded runways at airports would also hurt the region’s broader economy, she said.
Only an extra foot of flooding could submerge roads in Marin County. Big tech companies like Google and Oracle are perched on the edge of the rising bay. Thousands of homes and businesses are built over ancestral creeks and bay fill, Leal said.
Some parts of the Bay Area are already incorporating climate information into their planning. For instance, San Francisco’s “Great Highway” is being re-routed because of erosion. Voters in the nine counties surrounding the bay recently passed a $12 annual tax on every parcel of real estate, with the money going towards climate adaptations.
Climate science has repeatedly shown that global warming is increasing the odds of extreme precipitation and storm surge flooding, says Noah Diffenbaugh, professor of earth system science at Stanford University.
While hurricanes like Harvey and Irma are complex events — and can’t be directly linked to climate change — it is well established that global warming is already influencing many kinds of weather extremes, according to Diffenbaugh’s research.
In the Bay Area, we’ve already gotten brief glimpses into the future, when the alignment of the gravitational pull between the sun and moon create extra-high King Tides — and walkers along San Francisco’s Embarcadero find themselves up to their ankles in brackish water from the bay.
The Bay Area, like the rest of the world, has flourished during a time of relative stable sea level rise, Griggs said, noting that for about 8,000 years, seas have risen at a rate of less than 1 millimeter a year.
Eight of the Earth’s “megacities,” home to more than 10 million people each, are located along a coast, he said. About 3 billion people worldwide live in a coastal area.
But sea level is now expected to rise significantly over the next century because of the changing
global climate. The average global rate of sea-level rise is 3.4 millimeters a year — or 1.3 inches a decade. That’s more than twice the average rate over the 20th century and greater than any time over the past thousand years.
“Human civilization has never had to deal with significant sea level rise,” Griggs said. “That will be the biggest challenge that civilization has ever had to face, given the number of people who live along the coast.”
Part of the Bay Area’s flood risk is caused by slow and long-term rising seas, linked to melting ice in places like Greenland, Griggs said. But he said there also are shorter-term and more immediate risks, caused by high tides, storm surge and wave damage.
So far, the Bay Area has been spared the type of catastrophic flooding that routinely befalls cities like Houston, New Orleans and Miami, the experts said Wednesday.
Last January, the Bay Area was only 36 hours away from a potentially disastrous one-two punch: massive winter rains coupled with King Tides, Goldzband said.
When that happens, “that is when the world turns upside down,” he said. “We haven’t had that experience yet.”