Natural Disasters

1. Natural Disasters • John Gyakum (AOS) • John Stix (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. 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 10% probability of occurrence Recurrence intervals and probabilities

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. Meteorite impacts

26. The Cretaceous-Tertiary (K-T) extinction at 65 Ma • End of the dinosaurs and other species • In fact, about two-thirds of all species wiped out • 80% of all individuals killed off • Thereafter, mammals took over

27. Tsunamis TheGreat Wave off the Coast of Kanagawa, by Hokusai, a famous late eighteenth- and early nineteenth-century Japanese artist.

28. 4 case histories Alaska 1964 (earthquake-generated) Krakatau 1883 (caldera-generated) Unzen 1792 (landslide-generated) Grand Banks 1929 (submarine landslide-generated)

29. Volcanoes and volcanism • Volcanoes represent venting of the Earth’s interior • Molten magma rises within the Earth and is erupted either quietly (lavas) or violently (pyroclastics) Sakurajima Volcano, Japan Cinders were issued up to >2,500 m high 18 May 1991

30. Volcanic activity: pyroclastic flows • Pyroclastic flows are suspensions of hot pyroclastic material, air, and gas which descend under the influence of gravity • Their velocity is generally very high (50-500 km/hr) • This example is a flow from Mt. St. Helens

31. Avalanches

32. Avalanches were first imagined as giant snowballs which increased in size from accretion of underlying snow

33. Fully-developed powder avalanche due to cascading down near-vertical cliffs

34. Hurricanes

35. Hurricanes (continued)

36. Tornadoes

37. Floods New Orleans; August 2005

38. El Niño

39. Ice Storms

40. Web sites and readings • Definition of terms used in this course: • http://pdm.medecine.wisc.edu/vocab.htm • Useful general web sites: • http://www.colorado.edu/hazards/ (clearinghouse of disaster-related information) • http://www.colorado.edu/hazards/sites/sites.html (links to useful disaster-related sites) • http://earthobservatory.nasa.gov/NaturalHazards/ (current events) • http://www.paho.org (topics on disasters) http://cgdi.gc.ca/ccatlas/hazardnet/a_contents/content.htm (Natural hazard map of Canada) • http://www.esri.com/hazards/makemap.html (an interactive tool to make hazard maps for the USA) • http://www.hazpac.org (interactive hazard maps of the Pacific Ocean basin) • http://www.jpl.nasa.gov/earth/natural_hazards/natural_hazards_index.html (information on various natural hazards) • http://visibleearth.nasa.gov (images of various natural phenomena) • http://www.photolib.noaa.gov (images of various natural phenomena)