♦ Locations of Vulnerable Environmental Resources
Assessing the hazard zones is helpful to identify whether they encompass valuable environmental, historic or cultural resources that may be vulnerable to
the hazard. Vulnerable resources could include features such as aquifer recharge zones, potable water sources, historic buildings, and other such features. If the
vulnera
vent could cause ting the damage
caused
ons or facilities at may be subject to disaster impacts. For example, it may be widely known that
ific wash out after every heavy rainstorm, or that a
certain
unity is exposed for each hazard. A judgment regarding the bility of these types of resources is known, then the Local Mitigation
Strategy can also consider mitigation initiatives to lessen the potential for damage.
♦ Hazardous Materials Facilities
Facilities where hazard materials are stored represent a unique situation regarding their vulnerability to disasters, for the impact of the e
the accidental release of dangerous materials, further exacerba by the disaster itself. It will be worthwhile to assess the vulnerabilities of
any such facilities that are located in the identified hazard zones.
♦ Historical Information Regarding Hazard Vulnerabilities
An important source of information to complete the vulnerability assessment process is local knowledge regarding specific locati
th spec
sections of roadways electrical transmission line fails often during windstorms.
2.3 Vulnerable Analysis
The final step in the vulnerability assessment process is to use the information gathered and analysis conducted to date as a basis to estimate the risk
to which the comm
13
risk of
s. There are several factors to consider when assessing vulnera
od of the event occurring again in the future. This ra
long-term 30 years at least data. Examination of past events helps to determine the like
of ven
in the future.
Table 2.1 Frequency scoring Source: Heinz, 1999
Approx. Rec
ce years
Approx. Probability
Frequency Score
a specific type of event will be an important tool for used later in prioritizing mitigation initiatives as they are developed from the vulnerability
assessment results. Vulnerability
is concerned with the qualitative or quantitative examination of the exposure of some component of society, economy or the environment to
natural hazard bility, and these include: the frequency of the hazard, the size of the area
affected by the disaster, and the severity or amount of damages that has resulted.
1. Frequency
Evaluating the number of times that the natural hazard has impacted in the past provides a measure of the likeliho
ting is derived from an investigation of trends in the lihood
similar e ts occurring
urren Annual
Subjective Description
1 100.0 Frequently recurring hazards, multiple
recurrences in one lifetime 5
50 2.0 Typically occurs at least once in lifetime of
average building 4
250 0.40 ccurring at least once in lifetime
of average building 3
25 chance of o 500 0.20
10 chance of occurring at least once in lifetime of average building
2 1000 0.10
Highly infrequent events, like maximum considered earthquake
1 2500 0.04
Unlikely event
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2. Area of Impact
A second criteria used in evaluating vulnerability to natural hazards is to determine the impact, or size of the area affected by the disaster. Some hazard
events impact only a small region, while others can affect the entire area. The area of imp
iate area is im
vent. Again, historical data is used to investigate damage and loss records of previous hazard events to develop an estimate of where
expected im cts or the a
ccur. able 2.2 A
g Source: Heinz, 1999
Mean Affected Area sq. milesevent
Subjective Description Area Impact Score
act determination indicates how much of the immed pounded by a single e
pa mount of property damage may o
T rea of impact scorin
No affected area 1
Highly localized city block scale 1
10 Single zip code impact
2 50
City scale impact 3
100 County scale impact
4 500
Regional impact e.g. statewide 5
3. Severity
Severity, e range of the
x Previous damage reports and other hist ical data e.g. newspaper articles,
personal accountings, video clips, etc, are used. Table 2.3 Severity scoring Source: Heinz, 1999
Severity Score Earthquake MMI Hurricane SSI Average Flood Elevation ft
or magnitude criteria, is used to determine th severity of damage from minor to devastating e pected from a single event.
or
0 3 0 1
4 1
1 2 5 2
8 3
7 3
12 4 9 4
14 5
12 5
24
15
2.4 Use of GIS In Natural Hazard Assessments
