Preface. I first published this in June 2014, but thought I’d re-update it now that $2.5 million is going to be spent by Resilient by Design on 10 teams to come up with solutions for rising sea levels.  They failed to come up with anything useful:

1. Resilient by Design Bay Area Challenge Proposals Unveiled (Part 1)
2. Resilient by Design Bay Area Challenge Proposals Unveiled (Part 2)

The problem with levees and seawalls are that they just push the water to higher flooding levels where to protection exists.  See my energyskeptic book review of “Battling the Inland Sea” about the building of the levee system in California in the 19th century for more lessons to be learned from the past.

The only solution I can see that makes any sense is the one to dredge vast amounts of the bay to create wetlands that extend out from the shore the required distance.

Frederikse et al (2020) have found that without 58,000 large dams in the world holding back so much water, sea level rise would be around 12% higher today.  Since dams have a lifespan of 60 to 100 years on average, at some point that water will gush back into the ocean, raising sea levels.  It would take five times as many new dams to stop the current rate of sea level rise, with few places to put them.

Alice Friedemann   www.energyskeptic.com  author of  “Life After Fossil Fuels: A Reality Check on Alternative Energy”, 2021, Springer; “When Trucks Stop Running: Energy and the Future of Transportation”, 2015, Springer and “Crunch! Whole Grain Artisan Chips and Crackers”. Podcasts: Derrick Jensen, Practical Prepping, KunstlerCast 253, KunstlerCast278, Peak Prosperity , XX2 report ]

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.

It’s not just California that faces this — globally, scientists have found that 269 airports are at risk of coastal flooding now. A temperature rise of 2C – consistent with the Paris Agreement – would lead to 100 airports being below mean sea level and 364 airports at risk of flooding. If global mean temperature rise exceeds this then as many as 572 airports will be at risk by 2100, leading to major disruptions without appropriate adaptation (Yesudian 2021).

References

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

Frederikse T et al (2020) The causes of sea-level rise since 1900. Nature 584.

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

Yesudian AN, Dawson RJ (2021) Global analysis of sea level rise risk to airports. Climate Risk Management