Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 51
4
Landslide Loss and Risk Assessment
An understanding of the economic and societal impacts of land-
slides is essential for informed decisions that address the risks
from landslides and other ground failure hazards. Documenta-
tion of injuries and deaths, property damage, economic disruption, relief
and repair costs, and environmental consequences is part of such an
understanding. Undertaking risk assessments of prospective losses for
failure-prone areas is an allied and equally important process. Loss and
risk assessments are essential for
· establishing a sound rationale for risk reduction programs based
on documented economic and societal impacts;
· evaluating the cost-effectiveness of proposed interventions for
landslide-prone areas;
· creating mechanisms for risk sharing involving the public and
private sectors through insurance, special assessment districts, or other
financial risk pooling;
· partitioning responsibility for landslide-related cleanup, repair,
and rehabilitation costs; and
· understanding the noneconomic consequences of landslides events,
especially to the environment (e.g., damage to critical watersheds).
The terminology of loss and risk assessment can be confusing. The
term loss assessment is generally used in reference to retrospective assess-
ments of the economic and societal consequences of a given event, and
more refined loss analyses go beyond an accounting of direct damages to
51
OCR for page 52
52
PARTNERSHIPS FOR REDUCING LANDSLIDE RISK
consider the economic and societal consequences of the event. The term
risk assessment is generally used in reference to systematic prospective
analysis of the extent of a hazard, the exposure of people and property to
that hazard, the likelihood of a damaging event, and the likely resultant
economic and societal consequences of that event. As articulated in the
National Research Council "red book" (NRC, 1983) on risk assessments,
risk assessments are the foundation for making decisions about the best
means for managing a particular risk. Risk assessments can involve quali-
tative characterizations or more sophisticated quantitative calculations,
and they can be based on scenarios describing individual events or proba-
bilistic assessments across a series of potential events.
4.1 LOSS ASSESSMENT
The need for and problems in obtaining usable assessments of eco-
nomic and other impacts of disasters constitute a problem that has been
recognized in a number of recent studies. The basic problem is articulated
in an NRC report addressing loss estimation for natural disasters: "There
is no widely accepted framework or formula for estimating the losses of
natural disasters to the nation. Nor is any group or government agency
responsible for providing such an estimate" (NRC, 1999, p. vii). This issue,
as it relates to landslides, was recognized with the 1980 publication of a
U.S. Geological Survey (USGS) Circular that documented the costs of
selected landslide events and called for systematic collection of loss infor-
mation (Fleming and Taylor, 1980; also see Schuster, 1996; Schuster and
Highland, 2001~. Box 4.1 describes the conceptual and practical issues
involved in undertaking systematic loss assessments.
The proposed National Landslide Hazard Mitigation Strategy identi-
fied the need for a ". . . framework for compiling and assessing a compre-
hensive data base of losses from landslides and other ground failure
hazards, which will help guide research, mapping, and mitigation activities
nationwide" (Spiker and Gori, 2000, p. 15~. The Federal Emergency Man-
agement Agency and the insurance industry are identified as prospective
leaders for two activities. The first is an assessment of the current status of
data on losses from landslides and other ground failures nationwide. The
second is to establish and implement a national strategy for compilation,
maintenance, and evaluation of data on the economic and environmental
impacts of landslides and other ground failures. The proposed strategy
designates federal and state entities as responsible for creating a "robust
national landslide hazards information clearinghouse system," local and
private entities as responsible for collecting and distributing needed
information, and the academic community as responsible for developing
and sharing information.
OCR for page 53
[~E LOSS ~~ R~K ~S=S~ENT
~3
Despite Me 1dent1Acat10n in We national strategy proposal of over
entities as appropriately leading loss assessment activ1Ues' Me USES and
Me Associabon of American State geologists (CASE) have already taken
Me lead by est^Ushing a partnership to undertake a loss assessment pact
protect (Davis ~ at.' 20037 Me USES provided Ending to Me ALSO for a
trial program to determine annual losses attributable to landslides in
seven states (results Tom Is pact program mere not livable at Me time
OCR for page 54
54
PARTNERSHIPS FOR REDUCING LANDSLIDE RISK
of publication of this report). The committee commends the USGS and
AASG for establishing this partnership and suggests that a series of such
pilot projects will be necessary to determine optimum approaches to the
collection and management of loss data that encompass both the economic
and the social consequences of landslides. The committee endorses the
USGS proposal for a "landslide loss information" clearinghouse to act as
the focus for loss information (see section 5.3) and urges the USGS and
state geological and other agencies to collaborate to ensure that appropri-
ate protocols for data collection and storage are established as part of the
National Spatial Data Infrastructure (OMB, 2002~.
The committee further recommends creation of a Learning from Land-
slides (LFL) program to constitute a focal point for documenting the losses
and other detrimental effects caused by landslides. Such a program could
be modeled after the existing Learning from Earthquakes program funded
by the National Science Foundation and coordinated by the Earthquake
Engineering Research Institute. This LFL program would fund reconnais-
sance teams comprised of relevant specialists to examine and document
notable landslide events and their impacts, including economic conse-
quences (see section 6.3~.
4.2 RISK ASSESSMENT
Risk assessments are the foundation for making decisions about the
best means for managing a particular risk. The challenges of undertaking
effective risk assessments include many of the issues associated with loss
assessments, as well as others noted in Box 4.2. Figure 4.1 illustrates the
role of risk assessment in guiding management of landslide risks, as pre-
sented in guidelines developed by the Australian Geomechanics Society
(AGS, 2000~.
Risk assessments provide informed options for risk management. As
shown in the upper half of Figure 4.1, risk assessments are prospective
analyses of the extent of a hazard, the exposure of people and property to
that hazard, the likelihood of a damaging event, and the likely resultant
economic and societal consequences of that event. Risk assessments can
involve qualitative characterizations or more sophisticated quantitative
calculations. They can be based on scenarios describing individual events
or probabilistic assessments across a series of potential events. Although
a number of American researchers and practitioners have been leaders in
the development of landslide risk assessments (e.g., Einstein, 1988, 1997;
Wu et al., 1996; Roberds et al., 1997), the range of procedures and their
role in decision making are in general poorly understood in American
practice, and consequently the use of formalized risk analyses is limited.
OCR for page 55
LANDSLIDE LOSS AND RISK ASSESSMENT
55
A nationally coordinated approach to publicizing landslide risk assess-
ments offers the opportunity for broader dissemination and understand-
ing, particularly at the local level.
Risk assessments are not just technical undertakings. As emphasized
in an NRC report that analyzed risk (NRC, 1996), risk assessments can be
important processes for informing relevant stakeholders about potential
consequences and for gaining consensus about appropriate steps to address
OCR for page 56
56
RISK ESTIMATION
RISK CALCULATION
RISK = (LIKELIHOOD OF SLIDE)x(PROBABILITY OF SPATIAL IMPACT)
x (TEMPORAL PROBABILITY) x (VULNERABILITY)
x (ELEMENTS AT RISK)
CONSIDERED FOR ALL HAZARDS
| ___ (or RISKCONTPOL)
PARTNERSHIPS FOR REDUCING LANDSLIDE RISK
lISK ASSESSMENT |
RISK EVALUATION
COMPARE TO LEVELS OF TOLERABLE OR ACCEPTABLE RISK
ASSESS PRIORITIES AND OPTIONS
CLIENT / OWNER / REGULATOR TO DECIDE TO ACCEPT OR TREAT
TECHNICAL SPECIALISTTO ADVISE
SK ANALYSIS |
l CONSEQUENCE ANALYSIS FREQUENCY ANALYSIS
ELEMENTS AT RISK ESTIMATE FREQUENCY
PROPERTY QUALITATIVE
l ROAD & COMMUNICATIONS QUANTITATIVE
SERVICES
l PEOPLE HISTORIC PERFORMANCE
l TRAVEL DISTANCE
l TEMPORAL PROBABILITY e.g., vehicles, persons RELATIVE TO INITIATING EVENTS
RAINFALL
l V U LN E RA B I Ll TY CONSTRUCTION ACTIVITY
l RELATIVE DAMAGE EARTHQUAKE
l l PPOEAE LITY OF l N.IUPY / LOSS OF LIFE | | SERVICES FAILURE / MALFUNC ON l
I SCOPE DEFINITION
| ESTABLISH BRIEF, PROPOSED METHODOLOGY | ~
HAZARD I DENT'FICATION l
I CLASSIFICATION OF LANDSLIDE e.g., slide, debris flow, rockfall
EXTENT OF LANDSLIDE e.g., slide, debris flow, rockfall
TRAVEL DISTANCE OF LANDSLIDE
RATE OF MOVEMENT e.g., creep, slow, fast
l
· 1-
I RISK TREATMENT
1
TREATMENT OPTIONS
ACCEPT RISK
AVOID RISK
REDUCE LIKELIHOOD
REDUCE CONSEQUENCES
TRANSFER RISK
TREATMENT PLAN
DETAIL SELECTED OPTIONS
IMPLEMENT PLAN |
POLICY AND PLANNING I—
l
1
it: 1
1- 1 ~
1
1
MONITOR AND REVIEW I , FEEDBACK
RISK CHANGES
MORE INFORMATION
FURTHER STUDIES
1 -
FIGURE 4.1 Schematic illustration of landslide risk assessment and risk manage-
ment decision processes.
SOURCE: Australian Geomechanics Society (AGS, 2000~.
OCR for page 57
LANDSLIDE LOSS AND RISK ASSESSMENT
57
potential harms. In this respect, an understanding of the risk posed by
potential landslides is a central ingredient of determining appropriate risk
management strategies to address that risk.
An example of qualitative approaches to risk assessment is the use of
a scoring system for rock fall hazards by the Oregon Department of Trans-
portation (Wu et al., 1996~. Highway segments are evaluated for the likeli-
hood of rock falls based on past frequency of rock falls, geological structure,
and other considerations. The potential hazard is then considered along
with potential for accidents (related to highway width and sight distance)
to produce a rock hazard rating score. A number of other states have
implemented similar approaches, and one role of a national strategy
would be to ensure that all states have access to techniques and informa-
tion that have been field-tested and refined.
An example of state-of-the-art quantitative risk assessment proce-
dures for landslide problems is their use in Hong Kong (Box 4.3), where
there is a substantial ongoing investment in improving hillside stability
(Ho et al., 2000~. Quantitative risk analysis has been applied to assess the
cost of managing risk and the direct and indirect benefits that result, to
optimize the allocations of available resources, and to identify areas of
concern for improvement. A recent review of trial applications of quanti-
tative risk assessment in Hong Kong (Lo, 2001) concluded that it can be a
very valuable tool in landslide risk management.
Although the proposed actions described above for documenting
landslide losses and risks are important and necessary for understanding
the consequences of landslides, they should be perceived as one compo-
nent of a dual approach. Risk assessments, together with loss analyses,
are essential for informed decisions about the management of landslide
risks. The committee strongly recommends that a national strategy for
landslide loss reduction establish and promote the use of sound risk
analysis methods for understanding landslide risks and making informed
loss reduction choices. Because the state of the art of such methods is
evolving, further development of landslide risk assessment methods and
documentation of their use are important components of a landslide
research program. Technical assistance in the conduct of landslide risk
analyses should be central features of educational and other outreach
activities established as part of the national program.
OCR for page 58
58
PARTNERSHIPS FOR REDUCING LANDSLIDE RISK
OCR for page 59
LANDSLIDE LOSS AND RISK ASSESSMENT
59
Representative terms from entire chapter:
landslide risk
