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HAZARD ANALYSIS
The process of defining a hazard …
Walter G. Green III, Ph.D., CEM
Emergency Management Process Series No. 1Copyright 2008 by Walter G. Green III
HAZARDS Existing condition or possible (under current
conditions) situation that has the potential to generate a disaster
Natural hazards – naturally occurring phenomena – weather, topographic, geological, hydrological, etc.
Human systems developed – caused by human activity, infrastructure, transportation, etc.
Conflict based – civil war, terrorism, nuclear war, etc.
THE ANALYSIS PROCESS
(1) identify possible hazards (2) characterize each hazard (3) apply a rating or assessment
metric (4) communicate the results
IDENTIFYING HAZARDS Consider two basic realities
There is no place on the earth’s surface that is without hazard
Almost any hazard can impact almost any place – fewer directly, more indirectly
The result is a list of hazards that is nearly endless for any specific location
How then do we narrow the field?
FINDING HAZARDS
(1) Response history (2) What has happened elsewhere (3) Hazard survey (4) Local disaster history (5) Current scientific knowledge (6) Environmental sensing Then do it all again on a regular
schedule
CHARACTERIZING HAZARDS
It should be obvious that hazards are not identical, not uniform, not exclusive, and not transposable
This means that we have to understand each hazard in the context of its time and place
CHARACTERIZING HAZARDS You must answer all of the following in terms of your
situation: Magnitude and intensity ranges? Time, and season? Duration? Timeline of development? Place and extent of impact area? Frequency? Can it be predicted? Related hazards? Cascading effects?
OUTCOMES
Higher magnitude and/or intensity = increased hazard
Time and season – a longer period during which these events typically occur = increased hazard
Duration - generally longer duration events = increased hazard
Timeline of development – generally shorter development = increased hazard
OUTCOMES
A critical location at risk or a wide-area impact = increased hazard
Higher frequency = increased hazard Events that can be predicted only
with difficulty = higher hazard Events that are related to and can be
triggered by or trigger other events = higher hazard
THE TIME HORIZON Very important to determine what the time
horizon of your assessment is A short time period (“in the next 2 years”)
Infrequent events become low hazard Frequent events become high hazard
A longer time period (“in the next 100 years”) Infrequent events increase in hazard
A very long time period (“the next 500 years”) Infrequent catastrophic events become
higher hazard
ASSESSMENT
Assessing hazards is a very difficult process Wide range of variability in the where,
when, what, and how bad of events
In many cases we have insufficient data or understanding to make highly accurate assessments
In other cases time precludes in depth analysis
TWO APPROACHES
Qualitative Assesses using fuzzy judgment Communicates in broad categories
Quantitative Assesses using defined criteria Communicates using numbers
QUALITATIVE ANALYSIS
[1] Define the levels [2] Accumulate information [3] Invite participation by experts [4] Describe the process and provide
an overview [5] Develop consensus
QUALITATIVE TERMS A possible standard:
Extreme - community can no longer function High – large number of deaths, similar
number of injuries, wide property damage, function difficult
Moderate – small number of deaths, larger number of injuries, wide property damage, function under strain
Low – no deaths, few injuries, little property damage, community services function close to normal
QUANTITATIVE ANALYSIS
There are a wide variety of approaches: Rating hazards by total number of key
factors Rating hazards by points for each key
factor Rating hazards by formulas that reflect
interactions between components of the hazard
TOTAL NUMBER High magnitude – X All year hazard – 0 Duration – X Timeline short – X Location wide area – X Frequency annual – 0 Not predicted – X Related hazards – 0 Cascading effects - 0
POINTS High magnitude – 6 All year hazard – 3 Duration – 8 Timeline short – 10 Location wide area – 10 Frequency annual – 1 Not predicted – 10 Related hazards – 0 Cascading effects - 0
THE FORMULA
Magnitude x 2 x number of months of duration
Plus area of potential impact divided by area of community x 10
All x 24 divided by warning time in hours plus a prediction constant
All x frequency of events in a 100 year period divided by100
THE FORMULA PROBLEM Some quantitative analyses use formulas to arrive
at numerical values for the hazard level Check to make sure the mathematics really
measure what they say they measure Common errors are to:
add factors that should be multiplied, or vice versa,
apply constants that are not constant, and mix values that are unrelated
FORMULA EXAMPLE
Your locality has hurricanes and tornadoes as its two primary natural disaster hazards
Which of the following is the best formula to express that relationship? Hurricanes + tornadoes = hazard Hurricanes x tornadoes = hazard Hurricanes or tornadoes = hazard Hurricanes and tornadoes = hazard
MIX TYPES? Do we create one single list of all hazards, or Separate lists of natural, human systems, or
conflict based hazards? And which goes first? The answer depends on:
The function the analysis performs, The programmatic structure of the
organization, and/or Current doctrine
PRIORITIZING
Ratings suggest we will rank order the outcomes
Highest to lowest, either overall or by class
Understand that the list is only a guide
But that decision makers will believe it is an absolute reflection of reality
THE FUTURE
Hazard analysis for today The typical hazard analysis
Or hazard analysis for tomorrow Project forward to the planning horizon Identify trends Identifying emerging hazards Allows proactive rather than reactive
planning for mitigation and preparedness
COMMUNICATION Typically a written report that describes the
method used, identifies the hazards, and ranks them
Report should clearly identify the time period for which it is valid, other restrictions to the scope, and underlying assumptions
Distributed as needed Used as the basis for vulnerability assessment
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