HAZARD ANALYSIS
The process of defining a hazard …
Walter G. Green III, Ph.D., CEM
Emergency Management Process Series No. 1
Copyright 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
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(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 widearea 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
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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
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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
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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?
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Hurricanes
Hurricanes
Hurricanes
Hurricanes
+ tornadoes = hazard
x tornadoes = hazard
or tornadoes = hazard
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
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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