The Bay Area will need an estimated $110 billion to combat sea-level rise in the coming decades, with the price tag for protecting San Mateo and Santa Clara counties reaching $11 billion and $8 billion respectively, according to a July study by the Metropolitan Transportation Commission-Association of Bay Area Governments (MTC-ABAG) and the Bay Conservation and Development Commission (BCDC).

The jaw-dropping figures highlight a daunting challenge: how will cities pay to protect themselves?

Only $5.5 billion is currently available to Bay Area governments through federal, state, regional and local funding programs. Approximately $105 billion will be needed in the next decades to expand wetlands, build higher levees, add tidal gates, construct sea walls and implement other mitigation measures.

These figures are based on the median cost estimate for all projects and could range between $81 billion and $142 billion, the Sea Level Rise Adaptation Funding and Investment Framework Final Report noted.

The study's analysis focuses on the inundation of shorelines by sea-level rise and storm surges. It excludes factors like stormwater precipitation, groundwater rise and freshwater inundation from rivers and tributaries, the authors noted.

While the cost of protecting the Bay Area may be whopping, the cost of inaction could be more than double of that, according to the report. And Santa Clara and San Mateo counties in particular could feel that burden, being areas with considerable high-tech, housing and power infrastructure along the San Francisco Bay.

Sea-level rise is "the existential crisis of our time," said San Mateo County Supervisor David Canepa, a Metropolitan Transportation commissioner. The rise, he added, threatens critical infrastructure such as airports, highways, roads, electric substations and wastewater treatment plants. This “will gravely impact San Mateo County and Peninsula cities.”

A sizable chunk of work in the Bay Area needs to be done in San Mateo County, but that should come as no surprise, Rachael Hartofelis, resilience planner at MTC-ABAG and the report's project manager, said in an email.

"San Mateo County has a lot of bay and ocean shoreline, and much of it will need to be adapted to protect from rising sea levels. The good news is that San Mateo County is taking an active approach to sea-level rise," she said.

About three-quarters of the adaptation projects needed in the county are already in a study or planning phase, according to the MTC/ABAG and BCDC Framework.

"The leadership of One Shoreline – San Mateo County Flood & Sea Level Rise Resiliency District is one reason San Mateo County is ahead of the curve compared to other counties around the state,” she said.

The figures mentioned in the study are just estimates, Hartofelis cautioned. The county will be able to refine its cost projections as more segments of the shoreline move from the study and planning phase toward specific project implementation, she said. The costs could go up or down.

Mountain View Mayor Margaret Abe-Koga, a Metropolitan Transportation commissioner who represents Santa Clara County cities, said in an email that current cost projections could escalate.

"Since the City of Mountain View developed a sea-level rise capital improvement program in 2012, we have seen cost escalations keeping pace with construction-cost inflation and the rising sea-level projections," she said.

The Mountain View City Council reviewed an update to the city's sea-level rise capital improvement program in 2021. In today's dollars, the cost would be close to $100 million, Abe-Koga said.

Sea levels in the San Francisco Bay Area have increased by 8 inches since local tide records began in the mid-1850s, according to the Palo Alto Sea Level Rise Vulnerability Assessment. The rate of increase has accelerated in the past several decades.

"Areas once considered to be outside of the floodplain will begin to experience periodic coastal flooding or permanent inundation. SLR (sea-level rise) will also cause the surface of the shallow groundwater table in low-lying coastal communities to increase, damaging buried infrastructure, mobilizing subsurface contaminants, infiltrating below-grade structures, and emerging aboveground as an urban flood hazard, even before coastal floodwaters overtop the shoreline," the report noted.

Fighting the sea

Regionally and locally, flood protection projects are currently underway. But it will take years to complete them, said Margaret Bruce, executive director of the San Francisquito Creek Joint Powers Authority (SFCJPA), adding that they don't have to happen all at once, anyway.

But they do need to be coordinated among the multiple agencies whose jurisdictions and regulations — local, state and federal— are involved. What's done in one area could deeply impact another, and requires analysis and planning.

The San Francisquito Creek Downstream Project, or "Reach 1," completed in 2019 through the San Francisquito Creek Joint Powers Authority, widened sections of the creek channel and built new levees that provide protection to 1,700 properties from a 100-year creek flood during a King tide. The project also provides an additional 3 feet of protection from potential future sea-level rise scenarios through the end of the century.

Downstream homes in East Palo Alto and Palo Alto are shielded. "This project likely resulted in avoided flooding in the lower portion of Palo Alto’s watershed, which might have otherwise occurred from the early 2023 heavy rains," city staff said in an email.

But the SFCJPA recently faced a disappointing reality after a new analysis found that its "Reach 2" project to replace the Pope-Chaucer Bridge in Palo Alto and Menlo Park, as was long considered, would endanger downstream areas by allowing the flow of too much water.

Of the major projects in both counties under development, many are in the pre-construction planning or design phases. The $545 million Shoreline Project will mitigate sea-level rise all along the Santa Clara County bayshore from Alviso to San Francisquito Creek.

Phase I of the Shoreline Project, currently underway in Alviso, is extending levee rebuilding and habitat restoration to reduce flood risks.

Phase II, which is being managed by the Santa Clara Valley Water District, is currently undergoing a feasibility study. Similar to the project in Alviso, the new levees would be the primary defense system for Palo Alto and Mountain View along the bay from San Francisquito Creek to Permanente Creek. Palo Alto is awaiting an update about the results of the feasibility study from the U.S. Army Corps of Engineers. If approved, construction in the area between Palo Alto and Mountain View would begin in 2030 with all levees completed by 2040, pending funding.

A separate Phase III of the project would focus on areas to the south, from Permanente Creek in Mountain View to Guadalupe River in San Jose.

In Palo Alto, the Shoreline Project improvements would not address secondary sea-level rise hazards such as shallow groundwater rise and stormwater flooding that occur landward of the levees. These hazards will be addressed through several existing projects identified in the city's Sea Level Rise Adaptation Plan process, the city said in the June 2022 Sea Level Rise Vulnerability Assessment.

Among Palo Alto's other projects, the city is elevating or waterproofing equipment and infrastructure at the Regional Water Quality Control Plant as it completes facility maintenance and upgrades.

The $5.1 million Palo Alto Horizontal Levee Pilot Project, which will be constructed between Harbor Marsh and the Regional Water Quality Control Plant, is in its design phase. Construction would begin in summer 2024 and is estimated to be completed by early 2025, according to the city. The levee would use recycled water from the water-quality control plant for irrigation of native-plant vegetation in the "living" parts of the sloping levee. The project is the first of its kind in the baylands and could be a model for other levees around the bay.

The city also has ongoing projects funded by the Stormwater Management fee to improve stormwater-drain capacity, pump stations, green stormwater infrastructure, maintenance and related projects.

Public Works completed the construction of Loma Verde Avenue stormwater-drain capacity upgrades, and East Meadow Drive and East Meadow Circle upgrades are scheduled to be installed within the next six months. The projects will eliminate flooding that occurs along East Meadow Circle due to water levels on Barron Creek.

Three other projects are scheduled in 2024 to alleviate localized flooding along East and West Bayshore roads: West Bayshore Road Pump Station and trunk-line improvements and Corporation Way system and pump station upgrades. Corroded, cracked or broken segments of storm drain pipes have also been replaced or lined in an ongoing storm-drain system replacement and rehabilitation project.

A planned $40 million Palo Alto Flood Basin Tide Gate Replacement Project, led by Valley Water, is on hold as Valley Water prioritizes other projects. As an alternative to immediate replacement of the existing tide gate, Valley Water and the city are currently exploring ways to prolong its life.

Abe-Koga said Mountain View has a sea-level rise capital improvement program, currently comprising 14 projects, including improved pump stations, salt pond restoration, levee improvements along lower Stevens Creek, mitigation at Charleston Slough and others (see map).

"Additionally, the City is collaborating with the U.S. Fish and Wildlife Service and the California Coastal Conservancy on the South Bay Salt Pond Restoration project. These initiatives aim to address flood risk management and habitat restoration, supporting the overall sea-level rise adaptation efforts," she said.

A comprehensive, collaborative approach

The backbone of many sea-level-rise projects, and those most likely to get state and federal financing, is collaboration between cities and counties and even the federal government.

The SFCJPA's Strategy to Advance Flood protection, Ecosystems and Recreation along the San Francisco Bay (Safer Bay) Project, a regional program along the Bay shoreline from the Redwood City-Menlo Park border to the Palo Alto-Mountain View border, will protect against a sea-level increase of up to 10 feet above today’s daily high tide. Safer Bay Phase 1 in East Palo Alto and Menlo Park is in the design phase and various stages of environmental analysis, Bruce said. The project will protect nearly 1,600 properties, mostly homes, within East Palo Alto and marshes managed by the U.S. Fish & Wildlife Service. In Menlo Park, the project will restore approximately 600 acres of marsh from former salt ponds owned by Fish & Wildlife.

The San Mateo County Flood and Sea Level Rise Resiliency District, also known as OneShoreline, was established in 2020 to bring the county and other partners together to best leverage funding and expertise as well as to coordinate on projects from neighboring jurisdictions in the region. Cities that are collaborating with OneShoreline include Menlo Park and Redwood City.

The Bayfront Canal and Atherton Channel Flood Protection and Ecosystem Restoration Project, costing approximately $9.5 million, which concluded construction in 2022, built two underground culverts that help prevent flooding in five mobile-home parks and businesses east of the U.S. Highway 101. Properties in the low-lying area have experienced flooding 40 times over the past 70 years, according to the district.

Redwood City, Menlo Park, Atherton and the county shared funding responsibilities for the design, environmental documentation and land access. The project collects stormwater runoff from the cities of Menlo Park and Redwood City, towns of Atherton and Woodside, and unincorporated parts of San Mateo County.

The project is relatively small but significant and shows how beneficial the mitigations can be. The area didn't flood during the 2023 winter storms, CEO Len Materman said.

In comparison, a mobile-home park in Belmont that is outside of the project area and has not yet been protected had significant flooding this year.

Another project that OneShoreline is managing — the Redwood Shores Sea Level Rise Protection Project — is being designed to protect the community of Redwood Shores, which is largely in Redwood City and was built on former marshes.

More than 3 miles of levees surrounding the community would be raised to meet FEMA requirements. OneShoreline, which is taking the lead on the project, is awaiting a final decision on a FEMA grant, Materman said.

OneShoreline is also managing a flood emergency response grant to create a coordinated county-wide "flood emergency preparedness and response" program, through collaboration with the San Mateo County Department of Emergency Management. The project includes upgrading and expanding the region’s Flood Early Warning System, public outreach, emergency response personnel training and creating a public flood-monitoring webpage.

The cost of doing nothing

While the cost of sea-level rise mitigation is staggering, the cost of inaction would be at least double. Even a partial estimate of the cost of doing nothing is anticipated to be more than $230 billion, according to the Framework study.

"Even the smart folks on the MTC planning staff couldn’t help me break down estimated losses by jurisdiction. But there’s certainly a cost for doing nothing and there likely will be significant impacts even to cities that are neither on the bay nor on the coast,” Hartofelis said.

According to her, Bayside neighborhoods in Menlo Park would be directly affected but even communities like Atherton, Portola Valley and Woodside would be “impacted by flooded wastewater treatment plants and other critical infrastructure.”

More than $1 billion in assessed value countywide is at risk of sea-level rise inundation and erosion in the near-term, she added, citing San Mateo County’s 2018 Sea Level Rise Vulnerability Assessment. Over the long-term, the estimate rises to nearly $39 billion.

The vulnerability study also found that during a 100-year event with 3.3 feet of sea-level rise, Redwood Shores would be entirely flooded. The U.S. Highway 101 would be submerged and parts of Woodside Road and downtown Redwood City would be inundated.

In San Mateo County a sea-level rise of 3.3 feet would impact 22,000 acres of land, 30,600 residential parcels and five wastewater facilities, according to a 2018 Stanford Public Policy Program report examining 22 bayside cities.

San Mateo County also carries the highest risk of damage in the Bay Area, a 2018 assessment by the County Office of Sustainability stated. At least 32% of the population lives in vulnerable areas. Environmentally sensitive areas – closed landfills, former industrial sites, underground storage tanks and other contamination sites – could be damaged by rising sea levels and could consequently contaminate the area. The county has 29 known sites containing hazardous materials or cleanup sites that are vulnerable to flooding in the near-term. As many as 665 sites are at risk in the long-term.

A San Mateo County Civil Grand Jury report in 2022, titled "San Mateo County: California's Ground Zero for Sea Level Rise," noted its bayside communities have billions of dollars of residential and commercial property at risk. Its five wastewater facilities and three airports, including San Francisco International, are at risk. Also at risk are the county's transportation systems, schools, medical facilities, homes and parks.

In Palo Alto, a 100-year storm tide could result in surface flooding of 4,400 residential parcels, two senior/disability centers, two schools and seven city facilities. Rising groundwater could potentially impact the foundation of 7,950 residential parcels in addition to city facilities, critical infrastructure — including electrical substations, the Palo Alto Airport and Municipal Golf Course and the U.S. Highway 101 — as well as schools and other structures, according to the city's assessment.

"The average daily high tide, with 36 inches of sea-level rise, is a tipping point when many areas of the city become vulnerable to permanent inundation," the assessment noted. "With 36 inches, daily high tides are projected to be high enough to overtop nearly the entire length of the City’s shoreline and could inundate a portion of Palo Alto."

Abe-Koga noted that Mountain View's North Bayshore Area, roughly bounded by Highway 101 to the south, serves as a regional economic hub, housing a wide range of technology company campuses. The recently approved Google North Bayshore Master Plan would introduce thousands of new housing units to the area.

"However, the North Bayshore Area is also the most vulnerable portion of the city, greatly impacted by projected sea-level rise. Although the exact extent of losses remains uncertain and depends on the eventual level and pace of sea-level rise, we anticipate significant local and regional economic impacts if proactive measures are not taken," she said.

Will all boats rise to the same level?

Some counties will experience more flooding sooner than others, so adaptation costs are not evenly distributed, the Framework study found. Some counties have planned and developed projects more than others, leading to questions about where new funding should go. The study pointed to underserved communities such as East Palo Alto and parts of Marin County.

According to Bruce, existing funding isn't equitable. One structural quirk of FEMA funding is the benefit-to-cost ratio, which rates projects based on the value of FEMA investment dollars compared to the value of the infrastructure to be protected. Cities with high-value developments receive funds to protect those structures, but in places such as East Palo Alto, where development has lagged, there aren't many large, valuable structures to protect.

Menlo Park, East Palo Alto's neighbor to the north, is a different matter. The bayfront part of Menlo Park scored a "nine" on FEMA's benefit-cost scale because of its valuable real estate, which includes Pacific Gas & Electric and Meta campuses.

Meta and PG&E entered a public-private partnership that qualifies them for an added $16 million to FEMA's Building Resilient Infrastructure and Communities grant funding, which supports states, local communities, tribes and territories for hazard-mitigation projects. Private matching is 25% of the grant. For small and impoverished communities, the split is 90% federal and 10% state or local match.

"There are no equivalent private parties with whom East Palo Alto can partner. The PG&E substation there is small," Bruce said.

"The consequences of destruction are extremely costly," she added. "The FEMA framework is institutionalizing inequity. We're missing many opportunities" to make up for those disparities.

But Hartofelis said: “The Safer Bay Project being led by San Francisquito Creek JPA will protect East Palo Alto and Belle Haven. As these plans evolve into projects ready to be funded, San Mateo County and the regional agencies (MTC, ABAG and BCDC) will need to align their efforts to ensure money is available from state, federal or regional sources to support communities that may have fewer resources to meet these challenges on their own."

Filling the funding gap will require a mix of funding types and amounts, the Framework report noted. "There is no single “magic bullet” that can fill a $105 billion gap," the study's authors said.

Safer Bay Phase 1 implementation, for example, is funded in part through a parcel tax, Department of Water Resources, CalOES/FEMA grants and a local match from the city of East Palo Alto. It receives funding from the San Francisco Bay Restoration Authority Measure AA program and other local sources.

A regional approach is critical, the Framework report found. Considered remedies include possible parcel taxes and ad-valorem taxes – a tax based on the assessed value of real estate. Both might be feasible options at the regional or county level, but they would need further study to ensure equitable results, the report said.

Funding through the San Francisco Bay Clean Water, Pollution Prevention and Habitat Restoration Measure AA, a $12 parcel tax approved by Bay Area voters in June 2016, is one example of how a few dollars per parcel can stretch to meet lofty goals. The measure raises $25 million annually, or $500 million over 20 years, to fund shoreline projects that protect and restore San Francisco Bay.

"Measure AA has been transformational. Our region is 10 years ahead of other areas," Bruce said.

Abe-Koga said, because counties and communities across the Bay Area could experience the impact of sea-level rise differently, "it is crucial to plan adaptation efforts at a unified regional watershed scale to mitigate the uneven impact and ensure equitable outcomes."

And "unified" is the operative word.

Materman emphasized the role of the private sector with respect to fundraising and community awareness.

"High-asset properties associated with corporations will benefit from resilience," he said.

The best way to build climate resistance in underserved communities is by packaging their needs with that of their neighbors, he said. A multijurisdictional approach with well-resourced communities that have well-heeled private companies – such as Meta in Menlo Park or Oracle in Redwood City – or with entities such as PG&E, which have substations to protect, can help stretch dollars for the benefit of all, he said.

In its recommendations, the San Mateo County Civil Grand Jury said that OneShoreline should consider establishing and administering a low-interest revolving loan fund to enable jurisdictions to prepare the initial engineering and planning necessary to obtain federal and state financial support.

But beyond raw dollars, cities and counties will need to revise their zoning ordinances to adapt to the rising seas, Materman said. And perhaps building would need to be prohibited in some shoreline areas.

The San Mateo County grand jury urged all residents to keep themselves informed regarding the risks.

"The glaciers are melting, and the clock is ticking," it said.