1. Natural Disasters
John Gyakum (AOS)
Souad Guernina (EPS)

2. What are we talking about ?
DISASTER:
dis - unfavourable
astro - stars
To the ancients, disasters were precipitated by the stars

3. Our role as scientists
In a sense, the essence of science is to be able to PREDICT natural phenomena, to REDUCE their effects

4. Katrina, Monday 29 August 2005, 0715 hours Zulu time

5. Courtesy Washington Post

6. Courtesy Washington Post

7. Katrina reaches Montreal

8. Some destructive natural events
Earthquakes: local to regional
Floods: local to regional
Hurricanes: regional
Tsunamis: regional to global
Meteorite impacts: regional to global

9. Relative energies of selected phenomena
Comparing energies and equivalent magnitudes for natural phenomena (from Brumbaugh, 1999)

11. Some important definitions
Hazard: potential threat to humans and their welfare
Risk: probability of loss (deaths, injuries, damage, disruption of economic activity) as a result of a particular natural event
Vulnerability: potential loss, or degree of loss, from the event (e.g., 0=no damage, 1=total loss)

12. Definitions (ctd.)
Disaster: a hazardous event affecting a community in an adverse way such that essential social structures and functions are disrupted

13. Definitions (ctd.)
Prediction and forecasting: statement that a particular natural hazard will occur with a given probability during a certain time frame in a specified geographic area
Mitigation: efforts to reduce or minimize the effects of natural hazards on a community

14. Risk of death1 Volcanic eruption: 1 in 30,0002
Asteroid impact: 1 in 20,0002
Earthquake: 1 in 200,0003
Lightning: 1 in 130,0003
Tornado: 1 in 50,0003
Hurricane: 1 in 25,0003
Airplane crash: 1 in 20,0003
Auto accident: 1 in 1003
1to an individual over a 50-year period
2worldwide
3USA only

15. A question for all of us
Why do people live where they do ?

16. People’s reactions to crises and disasters
Anger at scientists, officials, etc.
Frustration, especially if event is long-lived
Skepticism, which can be fostered by the media
Denial
Suspicion…a “plot”
Refusal to evacuate; people feel safest in their familiar surroundings

17. Prediction of natural phenomena
Where are we ?
Long-lived vs. short-lived events
Predictable (hurricanes) vs. unpredictable (earthquakes) events
Problem of human time vs. geologic time
Probabilities of scientists vs. exact date and time of ordinary people

18. Scientific understanding of natural phenomena
Occam’s Razor: when several conflicting hypotheses or explanations are proposed for the same set of observations, the best explanation is that with the fewest independent assumptions

19. Causes and effects
A cause-and-effect relationship - and associated predictions - is an inherently deterministic view
It works only with events whose outcomes occur with nearly 100% probability, e.g., flooding as a result of tidal forces

20. Unpredictability Mother Nature is non-deterministic
Individual events are inherently unpredictable
This requires a statistical approach such as probabilities, since we don’t fully understand many natural processes

21. Recurrence intervals and probabilities
Recurrence interval: average time interval between the occurrence of two events of given magnitude
An example is a flood of 6 meters which happens once every 50 years, on average
Or an earthquake of magnitude 5 which happens once every 10 years, on average

22. Recurrence intervals and probabilities
The flood: there is a 1 in 50 chance that such a flood will occur in any one year…
this corresponds to a 2% probability of occurrence
The earthquake: there is a 1 in 10 chance that such a quake will occur in any one year…
and thus a % probability of occurrence

23. An example of non-determinism
A flooded city from a swollen river…
…is the flood the source of devastation, or the dikes built to modify the course of the river?

24. Another example of non-determinism
Casualties and destruction from a volcanic debris flow…
…did the flow cause the disaster, or the siting of the town on debris flow deposits of older eruptions ?

25. Web sites and readings Definition of terms used in this course:
Useful general web sites:
(clearinghouse of disaster-related information)
(links to useful disaster-related sites)
(current events)
(topics on disasters) (Natural hazard map of Canada)
(an interactive tool to make hazard maps for the USA)
(interactive hazard maps of the Pacific Ocean basin)
(information on various natural hazards)
(images of various natural phenomena)
(images of various natural phenomena)