Scientific Method, Forecasts, Prediction, and Risk Assessment

Our Hazardous EnvironmentGEOG 1110

Dr. Thieme

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 impactFrequency of impacts• Magnitude and Frequency are inversely

relatedLarge magnitude events occur less

frequentlyLarge 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 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...)

Human Dimension

• 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 Hazard Linkages

• "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...)

Natural Service Functions