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Quantitative vulnerability estimation for individual landslides
Estimation quantitative de la vulnérabilité aux glissements de terrain
Du J., Yin K.
China University of Geosciences (Wuhan), China
Nadim F., Lacasse S.
International Centre for Geohazards / Norwegian Geotechnical Institute (NGI), Norway
ABSTRACT: Vulnerability has not been systematically considered for landslides until recently, but is a fundamental component in
the evaluation of risk. Vulnerability depends on the landslide intensity, the characteristics of the elements at risk, and the impact of
landslide. A quantitative model is proposed to estimate the vulnerability of the exposed structures and individuals. The model ac-
counts for landslide intensity, different classes of vulnerable elements and the impact of both slow and rapid moving slides.
RÉSUMÉ : La vulnérabilité est un facteur important du risque associé aux glissements et n’a pas été considérée jusqu’à tout récem-
ment. Elle dépend de l’intensité et de l’impact du glissement et des propriétés des éléments exposés. L’article propose un modèle cal-
culant la vulnérabilité de structures et d’individus. Ses paramètres caractérisent l’intensité du glissement, tiennent compte de différen-
tes classes de vulnérabilité et distingue l’impact de glissements évoluant lentement et rapidement.
KEYWORDS: Landslide, Quantitative vulnerability evaluation, Intensity, Susceptibility
1 INTRODUCTION
The ISSMGE glossary of risk assessment terms defines vulner-
ability as the degree of loss to an element within the area af-
fected by the landslide hazard. It is expressed on a scale of 0 (no
loss) to 1 (total loss). In contrast to flooding and earthquakes, it
is not straightforward to define or assess, the vulnerability to
landslides, due to the complexity and range of the landslide
process (Leroi 1996). However vulnerability can influence the
losses to a greater degree than the hazard (Einstein 1988; Alex-
ander 2004). Despite this, it is an economic and political neces-
sity to quantify vulnerability (Varnes 1984; Alexander 1984).
Two different perspectives exist for the vulnerability estima-
tion: that based on the natural sciences and that based on the so-
cial sciences (Crozier 2004). Most often, the assessments of
landslide risk are based on the natural science approaches. Some
apply damage matrices (Leone 1996) based on qualitative (Car-
dinali 2002) and quantitative approaches (Fell, 1994). Concep-
tual frameworks for quantitative vulnerability estimation have
been presented (Düzgün and Lacasse 2005, Uzielli
et al
2008).
2 PROPOSED MODEL
Following Uzielli
et al
(2008) and Li (2010), the proposed
model defines vulnerability as a function of landslide intensity
and susceptibility of element at risk. The parameters are estab-
lished on the basis of the landslide impact mechanism and cate-
gories of vulnerable elements. The proposed vulnerability
model is defined by Eq. 1 and represented graphically in Fig. 1:
For
I
≤ 1-
S
V
= ½[
I
/(1-
S
)]
2
For
I
> 1-
S
V
= 1-½[(1-
I)
/
S
]
2
(1)
V
[0, 1] is the vulnerability of elements exposed to the threat.
For structures, 1 means that the structure is completely de-
stroyed, while values less than one represent the degree of dam-
age and 0 describing no damage. For individuals, 1 means loss
of life, while a value < 1 is the probability of loss of life.
I
[0,
1] is the intensity of landslide. An intensity of 1 means that the
landslide has the potential of destroying all elements in its path.
Fig. 1 Vulnerability (
V
) from susceptibility (
S
) and landslide intensity (
I
).
S
[0, 1] is the element susceptibility:
S
=0 means that the vul-
nerable element has high inherent resistance under impact. The
terms
V
,
I
and
S
are non-dimensional and the values of 1 and 0
indicate the highest and lowest boundaries for the three parame-
ters. To account for the landslide impact in the vulnerability es-
timation, two stages of deformation are considered: 1) a slow
deformation stage and 2) the failure (rapid movement) stage.
3 LANDSLIDE INTENSITY
The definition of vulnerability requires information on landslide
intensity (Guzzetti
et al
1996), which should include informa-
tion on the landslide severity degree and spatial dimensions.
3.1
Slow deformation stage
Under slow deformation, cracks and tilting may occur in struc-
tures located on the landslide, due to displacement and velocity
of the ground surface and foundation substrata. The intensity
parameters include landslide velocity and local deformation,
