There’s only one San Francisco Bay.
But the Bay Area is made up of nine counties and 101 cities, each with its own politics, local rules and shorelines, differences that can make it complicated to figure out how to protect billions of dollars of highways, airports, sewage treatment plants, homes and offices from the rising seas, surging tides and extreme storms climate change is expected to bring in the years ahead.
A new report released Thursday aims to make that gargantuan challenge a little easier.
The “San Francisco Shoreline Adaptation Atlas” divides San Francisco Bay’s 400 miles of shoreline into 30 zones, and recommends a range of options — from building more tidal wetlands to constructing concrete sea walls — for each zone, based on local conditions.
The scientists and planners ,who spent two years writing the 250-page document, hope it will serve as a guide for cities, counties and other agencies to work together from a common plan, rather than randomly building projects individually that could make flooding worse for neighboring areas.
“The problem is that the Bay Area is ground zero for sea level rise in California. We’re a bathtub. We’re a bowl,” said Warner Chabot, executive director of the San Francisco Estuary Institute, a non-profit scientific research group in Richmond that was a co-author on the report.
“Airports, highways and wastewater treatment plants are located right near the shoreline,” he said. “Even if you live in the foothills, if you want to flush your toilet, or if you want to get to work, or school, or the hospital, sea level rise is going to affect you.”
San Francisco Bay’s waters already have risen 8 inches since the mid-1800s. A tide gauge at Fort Point, next to the Golden Gate Bridge, has recorded measurements since 1850.
Recent studies by the U.S. Geological Survey, National Academy of Sciences and other scientific organizations estimate that, depending on the amounts of greenhouse gases released into the atmosphere in the coming years, the Pacific Ocean on the West coast — and in turn, the water in San Francisco Bay — will rise up to two feet by 2050 and up to five feet by 2100.
In recent years, during high tides in storms, waves have crashed over the seawall on San Francisco’s Embarcadero, flooding roads.
And the pace is accelerating. The 10 hottest years on Earth since 1880 all have occurred since 1998, according to NASA, NOAA and other federal agencies.
Planning has begun in many Bay Area cities. But as with controversies over where to build new housing or transportation projects, passions and gridlock can rise quickly.
Thursday’s atlas looks at 27 different options, including building tidal wetlands to absorb wave action, adding new beaches, constructing new levees, changing zoning rules and raising some structures.
“We aren’t telling people what to do. We are giving people tools so they can decide what to do,” said Laura Tam, sustainable development policy director with SPUR, an urban planning think tank that co-wrote the report.
The most vulnerable areas are places built generations ago on wetlands and parts of the bay that were later filled in. They include San Francisco and Oakland airports, Foster City, San Rafael, Corte Madera, East Oakland, San Leandro, Alviso, East Palo Alto and Redwood Shores, experts say.
“In Superstorm Sandy in New York, no one could imagine that New York City would flood, but the flooding went up to the historical shoreline,” said Julie Beagle, an environmental scientist with the San Francisco Estuary Institute. “Everything that flooded was built on fill. It will be the same thing here. The bay is basically taking back areas.”
Different places will need different strategies, she noted. Highway 37 in the North Bay, which flooded this spring, may need to be raised up on supports, like the Highway A1A causeway that connects the Florida Keys. Former salt ponds in the South Bay are being converted to tidal marsh, which dulls wave action. Airport runways will need to be built higher, and in some places it will make sense to let the bay waters reclaim undeveloped areas.
Overall, it’s cheaper to use natural solutions than to try and wall off huge sections of the shoreline with concrete. And natural solutions preserve birds, fish and other wildlife.
“What are we going to do about it?” Beagle said. “How do we organize ourselves to adapt, and not leave our children a bay that is surrounded by concrete walls? These are hard choices, they are really emotional for people. But sea level rise is not going to stop at our city boundaries. We need to find a way to work together.”
In 2012, Superstorm Sandy caused $69 billion in damage on the East Coast. Record storm surges destroyed seaside communities and sent flood waters pouring down the stairs in the New York City subway system, causing blackouts when the water hit electrical equipment. Afterward, former Mayor Michael Bloomberg outlined a $20 billion plan to protect the city.
Around San Francisco Bay, the Bay Conservation and Development Commission, a state agency that regulates construction within 100 feet of the bay shoreline, is working on studies with local communities to address sea-level rise. But the commission hasn’t yet made the tough political calls. New rules to limit what can be built where on the shoreline are at least six years away, said Larry Goldzband, executive director of the commission.
“You have cities, counties, scores of special districts that need to work on this plan so it isn’t seen as a top-down plan that is the subject of endless litigation,” he said. “There has to be a regional agreement.”
The final cost to protect the bay’s shoreline will almost certainly cost tens of billions of dollars. And apart from Measure AA, a $12-per home annual parcel tax that voters approved in 2016 to raise $500 million for wetland restoration and flood control projects, no one knows where it will come from.
“We’re going to have to go from a stroll to a sprint if we are going to stay ahead of the problem,” said Chabot. “Unfortunately in most cases it takes a disaster to accelerate the type of planning that is necessary. Hopefully that won’t occur here.”