Multi Hazardous Case Study, CA Bay Area Flashcards
Where is the multi hazardous case study?
Local scale - Bay Area
Specified place - San Francisco
Hazardous setting - California (Wildfires, earthquakes, landslides)
What do you know about this American State?
Climate
- El Niño
- La Niña
- Santa Ana Winds
- Chaparral vegetation
Major Cities
- California has a population of 39.5 million people, making it the most populous state
Economy
- largest economy in the US boasting 3.2 trillion dollars gross state product as of 2019
- if it was a sovereign nation, it would rank as the 5th largest economy in the world ahead of India and behind Germany
Details about the earthquakes ?
• San Andreas fault (part of a broader fault zone) marks a conservative plate boundary where two coastal plates slide past each other, parallel to the plate margin at differential speeds.
•More than 70% of California’s population live within 50km of a fault line. •An earthquake of Richter Scale 7 or above would have massive impacts.
•The soft basin sediments in LA lead to rapid shaking with 5 major earthquakes being recorded in the last 100 years.
•Earthquakes are shallow and so more destructive.
•San Francisco Bay has experience several large earthquakes too.
Details about volcanic eruptions?
There hasn’t been a volcanic eruption in California since 1915 (Lassen Peak)
• But there are volcanoes being monitored for potential eruptions, e.g. Lassen Peak, Mount Shasta, and the volcanoes around Mammoth Lakes.
Summary of hazards ?
The greatest hazard risk is on the west coast due to earthquakes, landslides and wildfires. This is where the major cities are located, which increases risk.
Wildfire and landslide risk is greatest in the north, whereas drought risk is greatest in the south-west.
The least risk in California appears to be from volcanoes which are in a linear belt.
Why do people live in this risky place?why
Positive attitude to life, risk-takers (American Dream) (Heritage of gold rush, oil and film industries)
• Economic growth draws internal and external migration
• People have a faulty perception of risk
• They want to live here so they deny the risk
• They expect someone else (government) to mitigate the risk
• Religious faith (Rely on God’s will / Can’t prevent ‘acts of God’)
• Secular version: Hollywood’s celebration of disaster movie/heroism
Are there any factors which make people vulnerable to these hazards in California?
• Idyllic Californian lifestyle associated with coastal living – greatest earthquake and landslide risk
• Steep slopes and unstable geology amplify risk
• Smog and heat drives wealthier citizens to live in hills – greatest landslide and wildfire risk
• Housing estates for 7m people surrounded by Chaparral biome (iconic ‘Western’ environment)
What factors reduce hazard vulnerability in California?
Earthquake resistant design
• Emergency Services + planning eg: Federal Emergency Management Agency
• Common cause and community resilience
How would you describe people reaction to the threat of hazards in California? (Their hazard perception)?
Faulty – denial as opposed to ignorance
But too many interlinked risks to calculate accurately Blame people (arson) rather than accept nature (fire risk)
• Not fear
(people buying property after recent landslide in La Conchita!)
• Confidence in adaptation measures (Crystal cathedral) (some fatalism as religious society)
What are the physical vulnerabilities of the San Francisco Bay Area?
The Bay area is at risk of liquefaction due to soft sediments especially between the two main fault zones of the Hayward and the San Andreas faults.
• The southern area of the San Andreas has experienced the most major earthquakes over the last 40 years.
• This map suggests San Francisco city area is physically vulnerable to liquefaction, ground shaking due it proximity to the San Andreas fault and it is over due for a large earthquake.
What are the human vulnerabilities of the San Francisco Bay Area?
The San Francisco city area is home to 870,000 people
• The density of population is 18,573/sq mi
• The Golden gate bridge and the Bay bridge are designed
to withstand earthquakes but these present a risk to evacuation routes in the event of a large earthquake in the city.
Assess the risk to earthquake hazards in San Francisco Bay Area?
High physical risk
• Magnitude is high
• Shallow earthquakes – strong intensity
• Dense population susceptible to liquefaction near the bay coast
High human risk
• Dense population, but well aware of dangers and good community knowledge of strategies for resilience
• Bay area has many bottle necks in terms of transport infrastructure, but new bay bridge much stronger than old one.
• High value property, but technology helps to secure it and insurance is widely available
BUT – Wealthy, well educated population improves capacity to cope and therefore reduces vulnerabilities, however, locally there are risks such as liquefaction areas and vulnerable populations such as elderly
Overall
-Risk is high but reducing with new technology
-Risk is medium but increasing due to climate change and growing pressure from population ageing and migration
How community response and management can influence the impacts of the hazard
FEMA / California Governors Office / Community Groups cooperate to produce: Bay Area Earthquake Plan “Safety depends on you reading the plan”
Residents taught to:
• Store supplies
• Family contact plan
• “Stop, cover and hold”
4 Task forces
• Manage and repair infrastructure (movement of
emergency services after event – road, rail, sea)
• Healthcare planning / Family reunification
• Rehoming displaced residents
• Communication during and after event (maintain law
and order)
How the characteristics of the Bay Area influence the potential impacts of a hazard
Coastal, hilly, therefore landslides (floods) Soft sediment/loose gravels (liquefaction) Dense population (fast growing) – transport infrastructure most vulnerable
Therefore pressure on most vulnerable land and pockets of poverty (poorly engineered buildings) – highest risk for minorities
Rich often on surrounding slopes – well engineered (hazard proof buildings)
but high risk (despite insurance).
Value of land makes land-use zoning hard.
How politics and hazard perception can influence the potential impacts of the hazard
Faulty – deny the risk
Democrats dominate local government Believe in government action
Focused on public engagement to improve hazard response.
However, opposed to developments that might disrupt communities/heritage
This makes land use zoning hard.
