As climate change continues to affect cities, those in seismically active areas like San Francisco face the additional challenge of addressing seismic risks. San Francisco is located in a region that has long been regarded as being seismically active as it is along the San Andreas Fault. This city has over the years been forced to rethink its planning to come up with not only ways of dealing with earthquakes but also protecting the city from the negative impacts of climate change which has become a concern in the recent past. This makes it a remarkable example in the quest to create smart, resilient, and Transformer cities of the future.
Historical Earthquakes and Their Impact on San Francisco
San Francisco is a city whose history has had the greatest influence on several catastrophic earthquakes, in particular the one that took place in 1906. The earthquake, all of 7.9 magnitude, was accompanied by fires that burned most of the city, causing immense property damage. More than 80% of San Francisco had been rendered uninhabitable and many residents were rendered homeless. Thereafter, attention shifted to the building of structures that would be resistant to earthquakes hence the emergence of the seismic building codes that exist today.
The impact of the 1989 Loma Prieta earthquake was not as catastrophic as that of the 1906 disaster but still caused much destruction, especially in the Marina District, where many structures sat on landfills. A few structures collapsed as a result of soil liquefaction, highlighting the shortcomings of certain construction methods. As a result, existing building designs were modified and construction codes were strictly enforced. These past earthquakes have compelled San Francisco to pursue the agenda of strengthening measures against earthquakes concerning urban development plans that span several years.
The maps below illustrate the magnitude of the shaking as well as the likelihood of liquefaction and landslides. All of these data products are from the USGS. There are a lot of different ways to cause a landslide. The “driving” factors that drive this land downward (such as gravity) overwhelm the “resisting” forces that are preventing slope failure (such as the strength of the bedrock or soil), which is the first order relation behind slope failure (landslides). The Factor of Safety (FOS) is the ratio of driving forces to resisting forces.
FOS = Resisting Force / Driving Force
The slope is stable while FOS is greater than 1, and it fails and landslides occur when FOS is less than 1. These relationships are depicted in the following illustration. Take note of the role that the slope angle α can play in this ratio; the steeper the slope, the more driving forces the slope’s mass can contribute. The simplistic representation below does not accurately reflect the complexity of the real world.
Earthquake Resilience: Preparing for the Unpredictable
The city of San Francisco strives towards achieving earthquake resilience by taking measures that go a long way in reducing damage and ensuring quick recovery. Therefore, the city has some of the world’s most stringent building codes, especially for high-risk areas. The city undertook a campaign to address the risks posed by soft-story buildings following the Loma Prieta earthquake. Soft story buildings are multi-storied buildings having ground floors with large open spaces and are structurally weak. These retrofitting efforts mitigate the risk of these buildings crashing down due to seismic activities which greatly enhances the structural integrity of these buildings.
Apart from focusing on retrofitting structures, San Francisco’s Earthquake Safety Implementation Programme (ESIP) also seeks to enhance other important elements such as strengthening bridges, hospitals, and the public transport system. Such facilities need to be functional even after a calamity to help in the restoration process. In ESIP practices, the focus has been on making resilience a priority from the beginning by making sure that essential functions such as emergency service provision are possible soon after an earthquake. Public readiness is equally important, with several drills and campaigns designed to train the population on how to react to an earthquake.
Climate Change Adaptation: Mitigating Rising Risks
In relation to the efforts of the city of San Francisco against earthquakes, it also focuses on the impact that climate change has on its environment. Coastal areas are prone to flooding due to climate change and San Francisco takes this dimension very seriously as several of its coastlines are subject to flooding because of rising sea levels. The Embarcadero district, one of the worst hit, is also endangered by the flooding not only because of rising sea levels but also storm surges. To reduce this, the town has gone ahead and taken measures that include reinforcing the coastal walls, elevating the buildings above the water height, and considering a managed retreat approach in some cases.
Besides flood control, for instance, San Francisco is also working on stormwater management through green infrastructure to combat the urban heat island effect. The incorporation of greenery, porous surfaces, and vegetated rooftops mitigate the risk of inundation by soaking the excess rainfall into the ground. These areas also aid in cooling the environment in an extreme heat and humidity situation allowing the city to handle a wide range of temperature fluctuations. With these initiatives put together, it is intended that the city of San Francisco will be able to combat the challenges posed by both earthquakes as well as climate change, thus supporting a safer and healthier urban landscape.
Integrated Multi-Hazard Planning: Addressing Overlapping Risks
San Francisco’s urban planning approach considers earthquake, flood, and climate change risks assuming that these risks are often interconnected. The focus of the city’s strategy is on constructing buildings and facilities with the capability to resist earthquakes as well as climate change ensuring that essential services remain functional before, during, and after any given disaster. This way of looking at planning and designing works in San Francisco not only prepares the city for earthquakes or climate change, but it makes the city able to withstand both.
For example, the city is modernising utility systems to meet the challenges of both heavy seismic activity and flooding, to ensure that necessary provisions are in place even during emergencies. In line with San Francisco’s comprehensive view of resilience, there is an urgent need for urban spaces to be designed to cope with a range of interrelated threats. The city therefore stands a better chance of dealing with such extreme situations as climate change impacts and other disturbances that may last for a shorter period.
Case Study: The Embarcadero Seawall Resilience Project
One of the prime instances of the resiliency planning of San Francisco is the Embarcadero Seawall Resilience Project. The seawall, which was mainly built in the early decades of the 1900s, plays an important role in shielding the city’s coastlines against the rise in sea levels and earthquakes. However, with time and the rising sea, the wall is exposed to a lot more conditions that militate against its integrity. In response to these challenges, the city has settled on addressing concerns in two phases, both of which will see the enhancement of the levee to protect it against floods and earthquakes.
This project is primarily concerned with the protection of infrastructure but it also has an ecological component. The benefits of the project also extend to green conservation by upgrading the marine environment along the seawall so that the area is pleasing to the eye while preventing hazards. In addition, the Embarcadero project proposes the design of outdoor areas that combine the functions of parks and zones for people to stay in during emergencies. In this way, the city enhances not only the environmental protection of the territory but its urban security as well, making it possible to use the area even in extreme conditions.
Looking Ahead: Future-Proofing Critical Infrastructure
San Francisco’s pledge to ensure that all its infrastructure is ‘future-proof’ goes a step further with the adoption of sophisticated modelling approaches, which are used to forecast the city’s response to specific disaster predictions. Such models help city planners experiment with different measures and enhance their response systems, thereby ensuring that the city is always prepared for the worst. Moreover, the project planners look for possible ways of using smart technologies like sensors and data analytics to improve the on-the-spot decision-making processes during emergencies.
The city’s actions to protect its infrastructure are in tandem with more sustainable objectives that are geared towards building a long-lasting infrastructure with a focus on a more dynamic climate and the seismic resilient built environment. In light of the impending risks posed by climate change and fluctuations in seismic activities, these strategies will be important in guaranteeing the sustainability of the city of San Francisco.
With natural hazards like earthquakes and climate change-related risks experienced in many cities across the globe, the understanding of San Francisco’s urban planning offers important lessons to them. In doing so, the city has gone ahead of the curve in designing urban centres that are not only surviving and working but can also grow healthily during and after the emergence of such needs. More than this, through TexAs ongoing development of resilient infrastructure systems, public participation, and environmental stewardship, we show that cities can deal with the dual forces of nature and man.
Citations:
Patton, W. by: Jay (2023) Earthquake report: 1989 Loma Prieta! – jay patton online, Jay Patton online – The Center, Body, and Range of Technically Defensible Interpretations. The CBD of TDI. Available at: https://earthjay.com/?p=8992 (Accessed: 10 November 2024).
(No date) Changes coming to SF Seawall in coming months | Kron4. Available at: https://www.kron4.com/news/bay-area/changes-coming-to-sf-seawall-in-coming-months/ (Accessed: 10 November 2024).
(No date a) S.F.’s Embarcadero could be devastated by earthquakes and rising seas, study warns. Available at: https://www.sfchronicle.com/bayarea/article/S-F-s-Embarcadero-could-be-devastated-by-15578778.php (Accessed: 10 November 2024).
