The need to revamp transportation infrastructure in the face of sea level rise

I remember briefly feeling nervous the first time I landed at the San Francisco International Airport. The descent to the runway gave me a beautiful vista of cerulean waters and low-lying mountains, but the bay seemed uncomfortably close as the plane neared the runway. While my flighting discomfort was merely the irrational fears of a jet-lagged eleven-year old, the runways of the second-busiest airport in California do rest within a stone’s throw from the salty waters of the San Francisco Bay.

Both the San Francisco International Airport and the Oakland International Airport, which combined traffic 60 million passengers a year, sit only 10 feet above sea level. While allowing for spectacular views of the San Francisco Bay and its many bridges, the infrastructure is incredibly vulnerable to the menace that will threaten all coastal cities in the 21st century: the rising sea level.

According to current models, the Bay Area will face a 16-inch rise in sea levels as soon as 2050. Various government agencies and organizations have commissioned or conducted reports to measure the impact of sea level rise on transportation assets, along with the current conditions of transportation infrastructure. In fact, in March 2016, the City of San Francisco released a one-hundred page report detailing the city’s Sea Level Rise (SLR) Action Plan. Part of the findings indicate that the Bay Area’s transportation systems are faced with aging infrastructure and that key transportation assets are currently at risk of disruption from storm surge flooding or eventual submersion.

In the face of these threats, there are surprisingly few region-wide adaptive measures currently being implemented in the Bay Area to adequately address all of the transportation networks and assets that are at risk. Agencies are working to bolster particularly vulnerable areas, but more regional coordination and public action is required to successfully reinforce transportation infrastructure.

What’s at stake? Firstly, airports

There are three major airports in the Bay Area metropolitan area: the San Francisco International Airport (SFO), the Oakland International Airport (OAK), and the Norman Y. Mineta San José International Airport (SJC). SJC, the smallest of the three airports with 10 million passengers per year, rests 63 feet above sea level. SFO and OAK, contrarily, barely rise above the Bay’s waves.

With its small seawalls, SFO’s runways are currently protected from storms surges. However, Oakland International Airport remains highly vulnerable to flooding from its low-lying transportation infrastructure. Both the BART Oakland Airport Connector and Doolittle Drive, which connect the airport to the Oakland metropolitan area, are currently below-grade. With even a minimal increase of the sea level, the flooding of the commercial runway would become a regular event.

Disruption of either SFO and OAK would have tremendous economic consequences not just regionally, but also nationally and internationally. Roughly 1 million metric tons of cargo passes through the airports per year (440,000 metric tons of cargo passed through SFO in 2016, and 537,000 metric tons passed through OAK). There are no local alternatives to accommodate cargo movement and air passenger traffic, so the entire Bay Area and beyond would suffer the consequences of a large-scale disruption.

Ground transportation

It is not just the airports that are under threat: the Bay Area’s roadway and railway infrastructure would face serious encroachments and closures from a rising sea level, as well. At their current state, transbay routes and arterial roads along the shorelines will face significant threats from storm surges and eventual inundation, while the supports for at-grade roadways and railways are at risk of sustaining corrosive damage.

The bridges that cross the Bay — the Golden Gate Bride, the Richmond-San Rafael Bridge, the Bay Bridge, the San Mateo-Hayward Bridge, and the Dumbarton Bridge — have recently been retrofitted for sustaining strong seismic activity. The Metropolitan Transportation Commission (MTC) released a detailed report of the program at the end of 2016. The BART Transbay Tube is also currently undergoing a seismic retrofit. These decisions made by local government agencies were good moves for protecting the transbay infrastructure from both future seismic activity and from corrosive damage caused by the rising sea level; however, the bridge crossing locations along with both ground level and at-grade shorefront roads and railways are still at risk from flooding and climate-related liquefaction damage.


5,100 acres of waterfront land across the Bay Area is imperiled from sea level rise. Significant portions of the Alameda waterfront along with the entirety of Redwood Shores, home to many corporate parks such as the headquarters of Oracle Corporation and of Electronic Arts, rest at the current sea level. A tremendous amount of ground transportation routes and assets would be disrupted or even destroyed by a significant flooding event or by inundation.

Perhaps the most dramatic example of this danger is the vulnerability of the Oakland Coliseum BART Station. This station contains integral BART assets such as a traction power substation and a train control room, the damage of which would lead to a system-wide disruption. The tens of thousands of people who rely on BART for their daily commute would suddenly need to find alternate modes of transportation, thus contributing to the further congestion of Bay Area roadways.

The MTC has announced it will address this potential crisis by adapting the nearby waterfront with “living levees” (details on pg. ES-17 and ES-18 of this report). These living levees are attempts to restore the natural wetlands that existed in the San Francisco Bay prior to coastal development, and will protect vulnerable routes and assets without the need to spend significant amounts of money on inorganic seawalls. The MTC’s plan will see living levees line the Damon Slough, which runs mere feet away from the Coliseum BART Station (aerial depiction below).

Even with some high-risk sites now included in adaptive plans, there are many routes and assets that remain points of concern. Waterside routes like The Embarcadero along with connectors to seaports and airports, for example, are still at high risk. Their disruption would simultaneously affect ground, sea, and air transit.

Increased threat from liquefaction

The Bay Area’s transportation infrastructure is not only threatened by the rising tides themselves, but the impact said tides will have on the soil beneath the roads and railways. A recent study for the 6th International Conference on Earthquake Geotechnical Engineering found a significant correlation between SLR and an increase in liquefaction vulnerability.

Liquefaction is a process where saturated or partially-saturated soil loses its solidity in the event of an earthquake or other seismic activity, resulting in the soil behaving like liquid. Structures resting atop liquefaction zones face high odds of sustaining damage during an earthquake.

Significant portions of San Francisco’s shoreline development, such as the Marina District (shown above after the 1989 Loma Prieta earthquake) and the Embarcadero, were built atop reclaimed land. Violent shaking in these areas would liquify the artificial-fill soil, which if widespread could easily lead to billions of dollars of damage.

A United States Geological Survey map reveals that much of San Francisco’s eastern bank is currently within high risk liquefaction zones (areas in red shown below), including portions of I-80, I-280, US-101, BART, Muni light-rail lines, and the Caltrain line.

These already-susceptible areas will see an increase in liquefaction vulnerability from SLR, which would have drastic consequences for both intracity and regional transportation.

The Port of San Francisco owns and manages 7.5 miles of the San Francisco eastern waterfront from Hyde Street Pier to the India Basin. This includes the particularly low-lying Mission Bay and Mission Creek shorelines, which contain key transportation infrastructure such as the northern terminus of I-280, the arterial roads of 3rd Street and the Embarcadero, and the northern terminus of Caltrain.

Currently, even before factoring in SLR, one-hundred percent of this shoreline area is within a high risk liquefaction zone. A significant seismic event would severely damage infrastructure within Mission Bay, the Embarcadero, and even further inland into the South of Market (SoMa) neighborhood. With the additional damages of sea level rise accounted for in this scenario, such an event could cripple not just entire blocks of the city, but even regional transit systems for a prolonged amount of time. Electrified rail lines could be paralyzed by seismic activity or subsequent flooding, which would lead to dire financial and environmental consequences such as repair and drainage costs, or increased automobile traffic and air particle pollution.

What are the challenges to adapting the Bay?

With all of these potential hazards to Bay Area transportation infrastructure identified, a reasonable question to then ask would be: why are so few adaptive measures in the pipeline?

The answer to the question is rather nebulous and complicated, but generally can be divided in two categories: 1) the relative nascence of SLR adaptation discussions, and 2) the large amount of expenses and coordination required to adapt existing infrastructure.

Most government agencies that have conducted studies of SLR scenarios are still in the process of determining how to react to their findings. Furthermore, an effective region-wide response will require collaboration between various authorities, asset managers, and private interests. Coordinating on such a scale in a bureaucratic system takes a lot of time — time which is running out. As a result of these factors, there are few concrete strategies either forthcoming or underway to address a reality less than thirty-three years in the future.

Current solutions are not enough

Fortunately, many public and private sector organizations are attempting permanent fixes across the region. Urban planning organizations such as SPUR have generated policy suggestions (e.g. Mission Creek SLR Adaptation Study) and plans (e.g. Ocean Beach Master Plan) for both public and government consumption. The MTC has also taken steps in adapting existing portions of infrastructure and is targeting weak points in the region’s transportation networks for future revamping. These efforts involve many different regional actors, which sets the groundwork for future cooperation.

However, this future cooperation needs to coalesce around a regional plan that will address the Bay Area as a whole, which is extremely challenging with the current political infrastructure. Due to the sheer amount of municipal governments in the metropolitan area, there are many brick walls for regional consensus on future planning. Not only are the brick walls with coordination intrinsic within the fragmented, multifarious Bay Area, but are layered by a byzantine web of regulations and varied city-level interests that planners must navigate when attempting region-wide action.

These roadblocks to regional planning must be overcome. Cities like San Francisco, Oakland, and Redwood City do not exist within a vacuum — all of the coastal municipalities share the same shore and any future regional response to SLR must take into account their unique situations and problems.

Beyond the work that has already been done, further concentrated efforts to adapt the Bay Area transportation infrastructure will require more interest and engagement from a larger pool of people . The more brains involved with the brainstorming, the better solutions there will be for preserving the Bay Area.

If you are new to this issue, take your first step in getting involved and check out what organizations such as SPUR or BCDC are doing now to combat the rising tides.

San Diego-based writer. Interested in urban planning, languages, cultures, travel, history, and fiction.

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