North Bay traffic to suffer most in San Francisco Bay Area from sea level rise, says Stanford study

Rising sea levels will not only require bayside businesses to protect their property, but they will also disrupt commuting for thousands of residents in Solano, Napa, Sonoma and Marin counties by regularly flooding critical routes, according to a new study.

The Stanford University research, released Aug. 5, uses data from the San Francisco Conservation and Development Commission, providing a stark look at the state of getting around the San Francisco Bay Area when sea levels rise due to climate change.

The scenarios include:

  • With the area already seeing traffic backups returning to pre-coronavirus levels, a 1-foot rise will add a half-hour to the average commute. The North Bay would particularly be vulnerable because, unlike other areas, it has fewer alternative routes around the flooded areas.
  • Plus, that 1-foot rise at the U.S. Highway 101–Interstate 580 interchange in San Rafael could affect 522,000 weekday trips.
  • Rising by 2 feet, the sea level rise would affect downtown Napa, hindering plans to bring 6,000 jobs to the city.
  • And most impactful, any rise beyond 2 feet will threaten to cut a major North Bay commute route — state Highway 37 — known now for being severed by rainy weather.

The findings from the commission’s 700-page environmental rising tides report may be considered alarming to transportation officials and business leaders trying to operate in and move goods and workers in low-lying areas already struggling with traffic concerns. And given this global pandemic’s impact on remote work as well, those commute hours may be spread out throughout the day.

“We’re getting our real traffic patterns back. The Bay Area is back to 80% (of those patterns),” Caltrans District 4 spokesman Bart Ney said. “The North Bay already has problems flooding, but the problem is going to get way worse.”

Climate change equals Highway 37 under water

A 3-foot rise could deliver massive flooding on the notoriously low-lying Highway 37 that sweeps the entire North Bay from Solano and Napa to Sonoma and Marin counties along San Pablo Bay’s tidal marshes. Highway 37 submerging may well impact more than 40,000 daily vehicle trips.

The winter of 2018 that delivered 6 to 9 feet of snow in the Sierra Nevada range and double-digit inches of rain to the North Bay took over the highway with a river that ran through the road, prompting Caltrans to shut it down multiple times.

Caltrans is undertaking three major projects on the highway, intended to deal with rising tides, road safety and traffic capacity on this major 21-mile North Bay artery.

The corridor that involves waterways from the Napa River to Sonoma and Novato creeks, rail lines in Marin County and even a national wildlife refuge already brings heavy congestion during both weekday and weekend time periods — especially alongside Mare Island.

In December 2015, a memorandum of understanding was signed by other North Bay county transportation authorities to develop funding, financing and implementing projects to reconstruct the highway to “withstand rising seas and storm surges while improving mobility and safety along the route,” Caltrans wrote in its project report.

The project costs, which include the installation of a viaduct, amount to at least $4 billion, District 4 officials reported. The project work started in June 2019 and is due to be completed in 2040.

“The biggest issue here is (Highway) 37 sees commuters that aren’t just office workers. There are cleaners, landscapers, truckers and construction workers,” said Marin County resident Dana Brechwald, program manager for the commission’s Adapting to Rising Tides environmental report. “I just drove it, and it’s still packed.”

Brechwald noted major concerns with pockets of vulnerable communities along the corridor such as Bell Marin Keys, a neighborhood near Novato Creek because they’re low-lying and close to the few commute routes that exist in North Bay.

Other “high consequence” concerns include transportation hubs such as ferry ports, rail services and even downtown districts like Marin County’s working hub, San Rafael — which could experience flooding on city streets.

Lack of alternate routes presents further problems

The 205-page Stanford study revealed even more problems for the North Bay. For example, flooding in low-lying San Francisco Bay Area counties like San Mateo could affect commutes in our region 20 miles away because fewer alternative routes exist here.

Workers in the Bay Area are known to cover a wide territory in their commutes and daily work trips.

According to the traffic study, 20% to 50% of Santa Rosa residents would face flood-related commute delays, despite being disconnected from most hazards caused by the rising waters.

What’s different is that on the Peninsula, Interstate 280 is an alternative to Highway 101. Oakland’s Interstate 880 is vulnerable to traffic congestion, but Interstate 580 provides an alternative, Metropolitan Transportation Commission spokesman John Goodwin pointed out.

“There’s no question this is of concern. We have essential workers of all sorts moving across the bay. We need to look at redundancy,” Goodwin said.

Solutions to the rising sea levels all over the Bay Area will require a multi-pronged approach, including where businesses, transportation hubs and highways are located, according to Brechwald.

“It will take something that has nothing to do with building a wall. You’d have to build it around the whole Bay Area, and that’s not feasible,” she said. “It will require leadership.”

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