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