Natural Hazards Flashcards
Earth Processes and Energy Sources
Earth processes driven by Earth’s internal heat: portions of the Rock Cycle, plate tectonics, earthquakes, volcanic eruptions, tsunamis
Earth processes driven by insolation: portions of the Rock Cycle, hydrologic cycle, atmospheric and oceanic circulation, severe storms, river floods, coastal erosion
Earth processes driven by gravity: landslides, snow avalanches, river flow
Naturally occurring Earth processes become hazardous when they threaten human populations
How to classify natural hazards
Geologic – earthquakes, volcanic eruptions, tsunamis, landslides; links to Rock and Tectonic Cycles (see Fig. 1.8, p. 11)
Atmospheric – tornadoes, hurricanes, heat waves; droughts, blizzards; links to the Hydrologic Cycle
Hydrologic – river floods, sea-level rise, coastal flooding; links to the Hydrologic Cycle
Biologic – epidemics of plant, animal, and human diseases, wildfires, mass extinctions; links to Biogeochemical Cycles and food webs
Technological/social hazards and disasters: are directly generated by humans without the interaction of natural processes
Hazards are commonly linked to each other as well as the environment in which they occur (e.g. earthquakes and tsunamis, or volcanic eruptions and lahars)
Hazard
Probability that a specific damaging event will happen within a particular time.
Risk
Derives form a combination of hazards, exposure, vulnerability, coping capacity
Exposure
Overlap of hazardous process with human populations and infrastructure
Vulnerability
Susceptibility of human populations to a hazardous event
Damage to infrastructure; loss of life
Loss of livelihoods; physical displacement; psychological impacts
Coping Capacity
Ability of populations to respond to and or reduce negative impacts of a hazardous event
Estimating Risk
Risk = Likelihood x Cost
Likelihood
An estimate, based on previous events, referring to the chance of a hazard happening in a specific amount of time
Cost
Refers to the impact of a particular hazard
Damages to property and infrastructure
Number of persons seriously injured or fatalities
What are natural disasters?
Emergency Management Framework for Canada’s defines a natural disaster as meeting one or more of the following criteria:
10 or more people killed
100 or more people affected/injured/infected/evacuated or homeless
an appeal for national/international assistance
historical significance
significant damage/interruption of normal processes such that the community affected cannot recover on its own
Natural Catastrophes
Catastrophes are associated with greater numbers of causalities and destruction and infrastructure
The event has consequences well beyond that area/region directly affected by the event.
recovery will demand large and long-term expenditures of time, human effort, and money
An increase in the number of natural disasters
There is a overall worldwide trend that the number of natural disasters is increasing
In Canada this has been associated with:
A decrease in lives lost, but an increase in economic losses…why?
Canada’s vulnerability to disasters is increasing.
There is a focus on recovery and some mitigation efforts in Canada.
Magnitude
refers to the strength and sometimes the intensity of the hazard.
There are several different quantitative scales used to compare the magnitude of events:
• Richter scale vs. moment magnitude vs. Mercalli intensity scale for earthquakes
• Volcanic explosivity index (VEI)
Frequency
refers to how often the event is likely to occur
Reoccurrence Interval
Estimate of the interval of time between events of a certain intensity or size
Magnitude-Frequency Relation
There is generally an inverse relationship between magnitude and frequency, the larger the magnitude, the less frequent the event.
Duration
refers to the length of time the event lasts. hours, days, weeks, months.
Extent
refers to the size of region affected by the event. hurricanes and tornadoes occur at different spatial scales
Spatial Predictability
Refers to where hazardous are located or centered (spatial) and to some extent or not the hazard can be predicted.
Speed of Onset
Refers to the speed at which the peak of the hazard arises; may be rapid, moderate, or slow
The speed of onset affects the time available to predict the event and to evaluate those at risk accordingly (e.g. Mount Pinatubo, 1991); predictions at the onset of the climactic eruption led to the evacuation of tens of thousands of people from the surrounding areas
Rapid Onset
Develop with little warning and strike rapidly
Moderate Onset
Develop with some warning (e.g. volcanic eruptions, floods)
Slow Onset
Take years to develop (e.g, drought, disease epidemics.)
Understanding Past History
Natural hazards are recurrent events
• To evaluate risk, we need to understand the geologic history of a region, often extending back hundreds or thousands of years
• We can look to maps, aerial photographs, and satellite images for recent changes in the landscape
• We often need to examine the geologic record for further evidence of past events (e.g. tsunami, landslides, lava flows)
Event Profiles
Event profiles are a common way of comparing different natural hazards and the physical processes or attributes that they share.
Primary Effects
Occur as a result of the natural process itself.
Buildings collapse due to earthquake.
Secondary Effects
Occur only because a primary effect has caused them.
Fires ignited because of earthquake.
Tertiary Effects
Long-term effects caused by the event
Cholera epidemic after an earthquake
Physical Vulnerability
living in close proximity to hazard-prone regions
Social Vulnerability
differences in availability of resources and aid
Structural Vulnerability
integrity of the built environment
Economic Vulnerability
variations in ability to respond to hazards based on differing economic systems
Cultural Vulnerability
examines the roles that customs, beliefs, values, social organization, and knowledge play in society’s policies and behaviour
Institutional Vulnerability
refers to the capacity of the governing system to protect society from hazards
Disaster Management
: includes public policies, strategies, and practices with the aim of preventing, managing and reducing the impact of disaster.
There is growing recognition that countries must shift to pro-active (pre-event) rather than re-active (post-event) responses to disasters
Preparedness
Planning and facilitating an effective response to a hazard event
Response
Actions taken immediately before, during, and after a hazard even to protect people and property
Recovery
Actions taken after a hazard to restore critical systems and return to a community to pre-disaster conditions
Mitigation
Actions taken before or after a hazard event to reduce impact on people and property
Pre-Event Mitigation
- Land-use planning • Insurance • Evacuation • Personal preparedness • Artificial control of natural processes • Building codes (pre)
Post-Event Mitigation
- Homeless shelters
- Emergency food, water and medical services
- Search and rescue efforts
- Firefighting
- Clean-up
- Building codes (post)
Prediction
A statement of probability that a precise event based on scientific observation
Forecasting
Identifying the conditions by which a particular event may occur
Warning
A statement of high probability that a hazardous event will occur
