Download Physical Geology

Our Hazardous Environment
GEOG 1110
Dr. Thieme
Scientific Method, Forecasts,
Prediction, and Risk Assessment
Scientific Method
• make observations
• formulate a hypothesis
• test the hypothesis with new observations
• draw conclusions (build a "theory")
Scientific Hypothesis
• a tentative assumption that is made for
the purpose of a study.
• testable against data obtained by
experiment or from field observation
• disproving your hypothesis thereby
confirms its opposite or null hypothesis
• Observation: A landslide occurred and
destroyed three homes
• Hypothesis: Water on the hillslope,
seeping from a buried waterline, caused
the landslide
Risk Assessment
• using statistical methods to quantify
the risks involved in a particular action
• risks are compared and contrasted
before deciding how to act
• risks are evaluated in order to identify
the causes of a medical condition or an
environmental problem
Risk
• probability calculated as a fraction:
– 0 (certain not to occur)
– 1 (certain to occur)
• multiplied by the consequences
• consequences can be harm or loss to:
–
–
–
–
people
property
economic activity
public service....
Risk Analysis
• estimate the probability that an event
will occur and the consequences
resulting
• Los Angeles has a 5 percent chance of a
moderate earthquake (p = 0.05)
Risk Analysis
• large events have lower probability than
small ones
• but consequences tend to be greater
Acceptable Risk - the risk that society
or individuals are willing to take
• businesses calculate risk in economic
terms
• individuals also incur risk
Risk Analysis and Planning
•
•
•
•
delineate areas where hazards occur
identify the processes responsible
attempt to control nature ("flood control")?
provide maps and information to planners and
decision maker in order to
• avoid putting people and property in harm's
way
Avoiding Disasters
• Land Use Changes: Avoid building on
• floodplains
• areas where there are active landslides
• places where coastal erosion will occur
• Insurance (flood, earthquake, etc...)
• Evacuation
• Preparedness - Train individuals and
institutions to handle large numbers of
injured and limit mass hysteria
Flow Path for Predicting or Warning about a Natural Disaster
Prediction and Forecast
• Prediction involves specifying date, time,
and size of an event (flood resulting from
tropical storm, etc...)
• Forecast is a prediction with a range of
certainty (and uncertainty!)
• For some types of natural hazard, neither
prediction nor forecast is really possible
• Some assessment of risk is always possible
Precursor Events
• linked with a hazardous event either
causally or statistically
• Foreshocks or unusual uplift of land may
precede earthquakes
• Volcanoes sometimes swell or bulge before
they erupt
• Sea may withdraw suddenly from a beach
before a tsunami hits
Natural Hazard Impacts
Magnitude of an impact
Frequency of impacts
• Magnitude and Frequency are inversely
related
Large magnitude events occur less
frequently
Large magnitude events have a lower
probability of recurring in any given time
interval
The "Golden Mean"
• Most of the work of forming Earth's
surface is done by events of moderate
magnitude and frequency
• "Bankfull" Floods
• Normal Wave Base in Nearshore Zone
• Mid-latitude Cyclone Storms
Natural Hazard Impacts
Direct Effects include people killed, injured,
dislocated, or otherwise damaged
Indirect Effects include
• emotional distress
• donations of money and goods
• financial disruption and funding of recovery
Disaster Recovery
Stages of Disaster Recovery:
• Emergency Work
• Restoration of Services and Communication Lines
• Reconstruction
Figure 1.16
Human Dimension
• Human Interaction with Natural Hazards increases
with population density
• Some technologies play a specific role in triggering
or mitigating disasters and catastrophes caused by
natural hazards
• Human Interaction with Natural Hazards is
discussed in each chapter of your textbook (Sections
2.8, 3.6, 4.6, etc...)
• Risk Assessment is important to understanding the
effects of natural hazards
• Minimizing the Risk from Natural Hazards is
discussed in each chapter of your textbook (Sections
3.9, 4.6, 5.7, etc...)
Natural Hazard Linkages
• Earthquakes produce
• landslides
• tsunamis
• Hurricanes cause
• flooding
• coastal erosion
• Volcanic eruptions cause
• lahars (catastrophic floods laden with ashy
mud)
• weather and even climate changes downwind
Natural Hazard Linkages
• Hurricanes (Katrina)
• high winds damage property and harm people
directly
• flooding that follows storm does more damage, for
which landowners may not be insured
• coastal flooding is linked to other coastal processes
• tropical storm intensity may increase in warmer
climate due to sea surface temperatures
• Earthquakes (Pakistan) and Volcanoes (Nevado del Ruiz)
• represent plate tectonic movements and in turn
trigger landslides, floods, tsunamis,....
Natural Service Functions
• "Ecosystem" services are benefits to humankind which
result from resources and processes supplied by natural
ecosystems:
• provisioning such as production of food and water
• regulating such as control of climate and disease
• supporting such as nutrient cycles and crop pollination
• cultural such as spiritual and recreational benefits
• preserving such as maintenance of biodiversity
• Natural Service Functions of Natural Hazards are
discussed in each chapter of your textbook (Sections 2.7,
3.5, 4.5, etc...)