The oceans are expected to rise around 1.4 meters by 2100. That assumes no surprises such as accelerated melting of the Greenland or Antarctic ice sheets.
Globalization and the distribution of food, coal, and other goods essential to staying alive depends on containerized shipping, trucking, and railroads. I used to work for a shipping line out of the Port of Oakland, so I wondered what clever techno-fixes there might be to cope with rising sea levels. Perhaps floating docks, new ships designed to offload offshore to smaller vessels, enormous barriers and dikes like in the Netherlands? It turns out a great deal of thought has been put into this, especially in California.
What Can be done?
Levees and Seawalls. Protecting California from a 1.4 meter rise in sea level would require 1,100 miles of levees and seawalls, and would cost roughly $14 billion (table 1) to build and $1.4 billion a year to operate and maintain it. No one is going to spend $14 billion on this, because there’s no guarantee the levees and seawalls would work, and the sea is going to keep rising for millennia, constantly overtopping whatever is put in place. An unusually large storm event can also cause it to rupture like the levees in New Orleans during Hurricane Katrina, even if it has been well maintained.
Paradoxically, it increases vulnerability. Hard shoreline protection is not as effective as natural shorelines at dissipating the energy from waves and tides. As a result, armored shorelines tend to be more vulnerable to erosion, and to increase erosion of nearby beaches. Structural flood protection can also increase human vulnerability by giving people a false sense of security and encouraging development in areas that are vulnerable to flooding.
Barriers are ecologically damaging and would harm the Bay’s salinity, sedimentation, wetlands, wildlife and endangered species, and increase sedimentation, making parts of the Bay shallower, while increasing coastal erosion.
A huge dike under the Golden Gate bridge won’t work for many reasons – it would cost four times as much as the Three Gorges Dam, and California gets huge floods (i.e. Arkstorm). If the dike were up to protect from rising sea levels, we’d be flooded from inland water with upstream flooding in the freshwater tributaries of the Bay.
Elevated development is a short-term strategy. Unless it’s on stilts directly over water, characteristics of shorelines are altered and will need protection just like low-lying development. Its advantage is merely that it is not threatened by sea level rise for a longer time. We don’t know if higher land or structures will support high-density, transit-oriented new development. Much of our region’s high-density neighborhoods and transit are near the Bay’s shoreline. If low-density development is allowed along the shoreline, it could increase global warming emissions, and may not warrant expensive protection measures in the future.
Floating development: structures that float on the surface of the water or that float during floods or tides. Floating development works only in protected areas, not in areas subject to wind and wave action from storms, such as the ocean coastline. This type of development has not yet been demonstrated in high-density cities. From an engineering perspective, many structures can be built to float, though they cannot be retrofitted to do so.
Floodable development: structures designed to handle flooding or retain stormwater. Floodable development could be hazardous. Stormwater, particularly at the seaward end of a watershed, is usually polluted with heavy metals and organic chemicals, in addition to sediment and bacteria. Large quantities of stormwater sitting on the surface, or in underground storage facilities, could pose a public health hazard during a flood or leave contamination behind. This could be a particular problem in areas with combined sewer systems, such as San Francisco, where wastewater and street runoff go to the same treatment system. Also, wastewater treatment systems that commonly treat the hazards of combined sewer effluent before releasing it into the Bay do not work well with salt water mixed in. If floodable development strategies are designed to hold and release brackish water, new treatment methods will be needed for the released water to meet water quality standards. Finally, emergency communication tools and extensive public outreach and management would be required to prevent people from misusing or getting trapped in flooding zones. Floodable development is untested. We don’t know if buildings and infrastructure can be designed or retrofitted to accommodate occasional flooding in a cost-effective way. It is not clear exactly how much volume new floodable development tools will hold. Some of the more heavily engineered solutions, such as a water-holding parking garage, may not turn out to be more beneficial than armoring or investments in upsizing an existing wastewater system.
Living shorelines. Wetlands are natural and absorb floods, slow erosion, and provide habitat. Living shorelines require space and time to work. Wetlands are generally “thicker” than linear armoring strategies such as levees, so they need more land. They also require management, monitoring and time to become established. Living shorelines are naturally adaptive to sea level rise, as long as two conditions are present. The first condition is that it must have space to migrate landward. The second condition is that they must be sufficiently supplied with sediment to be able to “keep up” with sea level rise. Due to the many dams and modified hydrology of the Delta and its major rivers, this is a concern for restoration success in San Francisco Bay. Wetlands will never be restored to their historic extent along the Bay, in part because of the cost of moving development inland from urbanized areas at the water’s edge. Important challenges for our region will be determining how much flooding new tidal marshes could attenuate, restoring them in appropriate places, and conducting restoration at a faster rate than we would without the looming threat of rising seas.
Managed Retreat. Abandon threatened areas near the shoreline. This strategy is a political quagmire. It involves tremendous legal and equity issues, because not all property owners are willing sellers. And in many places, shoreline communities are already disadvantaged and lack the adaptive capacity to relocate. In addition, retreat may require costs beyond relocation or property costs if site cleanup — such as to remove toxics — is needed following demolition
Consequences for the ports and airports
The main problem for shipping is not the port. It’s the roads and railroad tracks surrounding the port that are vulnerable, many of them less than 10 feet above sea level, and there’s nowhere to move them. Raising them would make them vulnerable to erosion and liquefied soils from floods or earthquakes.
An even bigger deal would be any harm done to the Port of Los Angeles-Long Beach, which handles 45%–50% of the containers shipped into the United States. Of these containers, 77% leave California—half by train and half by truck (Christensen 2008).
The Port of Los Angeles estimates that $2.85 billion in container terminals will need to be replaced. If the port is shut down for any reason, the cost is roughly $1 billion per day as economic impacts ripple through the economy as shipments are delayed or re-routed according to the National Oceanic and Atmospheric Administration 2008-2017 Strategic Plan. Replacing the roads, rails, and grade separations nearby would cost $1 billion. If the port’s electrical infrastructure were damaged, equipment such as cranes would be non-operational and cause delays and disruptions in cargo loading and offloading. These would cost $350 million to replace. The port also has an 8.5 mile breakwater that prevents waves from entering the harbor with two openings to allow ships to enter the port. An impaired breakwater would render shipping terminals unusable and interrupt flows of cargo. The breakwater has a $500 million replacement value and is managed by the Army Corps of Engineers.
Airports. Meanwhile, all of the airports in the SF Bay area are vulnerable to sea level rise, especially San Francisco and Oakland. In 2007, the Oakland International airport transported 15 million passengers and 647,000 metric tons of freight. San Francisco International Airport is the nation’s 13th busiest airport, transporting 36 million people in 2007 and handling 560,000 metric tons of freight $25 billion in exports and $32 billion in imports, more than double the $23.7 billion handled by vessels at the Port of Oakland.
County Miles of levees & Seawalls Cost 2000 dollars
Alameda 110 $ 950,000,000
Del Norte 39 $ 330,000,000
Contra Costa 63 $ 520,000,000
Humboldt 42 $ 460,000,000
Los Angeles 94 $2,600,000,000
Marin 130 $ 930,000,000
Mendocino 1 $ 34,000,000
Monterey 53 $ 650,000,000
Napa 64 $ 490,000,000
Orange 77 $1,900,000,000
San Diego 47 $1,300,000,000
San Luis Obispo 13 $ 210,000,000
San Mateo 73 $ 580,000,000
Santa Barbara 13 $ 180,000,000
Santa Clara 51 $ 160,000,000
Santa Cruz 15 $ 280,000,000
Solano 73 $ 720,000,000
Sonoma 47 $ 240,000,000
Ventura 29 $ 790,000,000
Table 1. $14,000,000,000 cost to build 1,100 miles of defenses needed to guard against flooding from a 1.4 m sea-level rise, by county.
Alice Friedemann in Oakland, California
Copeland, B, et al. November 24, 2012 What Could Disappear. Maps of 24 USA cities flooded as sea level rises. New York Times.
Grifman, P., et al. 2013. Sea level Rise Vulnerability Study for the City of Los Angeles. University of Southern California.
Heberger, M. et al. May 2009. The Impacts of Sea-Level rise on the California Coast. Pacific Institute.
Conti, K., et al. Nov 20, 2007. “Analysis of a Tidal Barrage at the Golden Gate,” BCDC
Preliminary Study of the Effect of Sea Level Rise on the Resources of the Hayward Shoreline. March 2010. Philip Williams & Associates, Ltd.
Sorensen, R. M., et al. Erosion, Inundation, and Salinity Intrusion Chapter 6 Control of Erosion, Inundation, and Salinity Intrusion Caused by Sea Level Rise. Risingsea.net