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

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

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

Katrina, Monday 29 August 2005, 0715 hours Zulu time

Courtesy Washington Post

Courtesy Washington Post

Katrina reaches Montreal

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

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

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)

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

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

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

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

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

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

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

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

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

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

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 10% probability of occurrence

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?

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 ?

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)