Document Actions

IJEGE-11_BS-Guadagno-et-alii

background image
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
71
DOI: 10.4408/IJEGE.2011-03.B-009
THE 1998 SARNO LANDSLIDES: CONFLICTING INTERPRETATIONS
OF A NATURAL EVENT
f
RanCesCo
m
aRia
GUADAGNO
(*)
, P
aola
REVELLINO
(*)
& G
eRaRdo
GRELLE
(*)
(*) University of Sannio - Department of Geological and Environmental Studies - via dei Mulini, 59/A – 82100 Benevento,
Italy. Tel: +39 0824 323634
Southern Italy
INTRODUCTION
The landslides affecting on 5-6 May 1998 the towns
of Sarno, Quindici, Siano and Bracigliano (Southern It-
aly; Fig. 1) represent a case history of great significance
both from scientific and technicalmanagerial point of
view. The casualties (161), the huge economic damage
and the severe destruction attracted great attention on
the part of the scientific community.
This interest also arises from the awareness that
the area of the Campania Region that can be consid-
ered subject to hazard is very large. About 2,000 km
2
of the region, a part of which is devoted to tourist ac-
tivity, may be considered at risk owing to the wide-
spread presence of human activities
As a consequence, problems connected with the
assessment of the areas at risk are key aspects in land-
ABSTRACT
Landslides affecting on 5-6 May 1998 the towns
of Sarno, Quindici, Siano and Bracigliano in South-
ern Italy represent a case history of great significance
both from a scientific and technical point of view. The
casualties, the huge economic damage and the severe
destruction attracted great attention on the part of the
scientific community. Following the landslides, both
the national and international scientific community
and technicians have given rise to numerous studies
in order to provide suitable elements for designing
remedial works. From the scientific side, till 2010
hundreds of articles and reports were produced con-
cerning researches carried out on the Sarno-type land-
slides. In order to make comparisons not only on dif-
ferent methodologies adopted but even on contrasting
interpretations and results concerning landslide trig-
gering and propagation mechanisms in a global and
comprehensive picture of the knowledge, more than
200 scientific papers on this type of instabilities, pub-
lished on national and international journals and con-
ference proceedings, were collected. Analyses on spe-
cific aspects of the landsliding frequently show huge
disagreements among different authors and research
groups. The discussion particularly focuses on land-
slide classification aspects, criteria adopted and their
real application. Wide-ranging ambiguities cause un-
certainties in applying landslide classification criteria.
K
ey
words
: Sarno-type landslides, classification criteria,
Fig. 1 - May 1998 landslides at Sarno
background image
F. M. GUADAGNO , P. REVELLINO & G. GRELLE
72
5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
slides because of the large variety of discriminating
factors (H
ansen
, 1984). Over the years, this fact led to
favour type-kind classifications better suitable, in the
case of landslides, for giving categorizations which
are not only descriptive but also behavioural..
Therefore, few comments are here reported on
sub-aerial landslide classification aspects and, in par-
ticular, on landslides of the flow type involving soils,
where the mass and “the general appearance is more
obviously that of a body that has behaved like a fluid”
(v
aRnes
, 1978). These instabilities should be consid-
ered as transition phenomena of the morphological ev-
olution between the field of the mass movements and
that of the mass transports (P
ieRson
& C
osta
, 1987).
At the present time, the most widely accepted clas-
sification systems in the international academic world
are those of v
aRnes
(1978), subsequently modified by
C
Ruden
& v
aRnes
(1996), and of H
utCHinson
(1988).
The first two suggest the movement mechanism and the
material type as basic discriminating factors, whereas
landslides are included in categories with similar kin-
ematic patterns in the last one (H
unGR
et alii, 2001).
In all cases, the morphology of landslide bodies
and, therefore, of detachment areas is one of the main
criteria in order to succeed in classifying slope insta-
bilities and defining mechanisms of movement. Mate-
rial types and properties are significant as well in iden-
tifying movement kinematic. Other features, such as
e.g. the velocity of the landsliding mass, help in giving
a better description of the assigned classification.
It stands to reason that the complexity of the pre-
disposing triggering factors can induce uncertainties
in defining the kinematic model of the landslide and,
consequently, incorrect evaluations in the classifica-
tion of phenomena.
As pointed out by H
unGR
et alii (2001), particularly
clear difficulties are associated to the classification of
landslides of the flow type, due to the significant ef-
fect of factors influencing the mass behaviour during
motion. As an example, the water content affects the
movement characteristics of more or less fluid masses;
in some channelled flows, it may induce those transition
conditions as described by P
ieRson
& C
osta
(1987).
Within the above-mentioned articles, the authors
mostly refer to the landslide classification of v
aRnes
(1978). Leaving out creep and solifluction, which can-
not be classed as landslides (C
oates
, 1977; H
uCHinson
,
1988), sub-aerial flow-like slope movements of en-
planning activities and in defining mitigation strategies.
Following the 1998 landslides, both the national
and international scientific community and techni-
cians have give rise to numerous studies and inves-
tigations in order to provide suitable elements for de-
signing remedial works.
From the scientific side, till 2010 more than 200
articles were published on national and international
journals and conference proceedings from different
research groups, individual scholars or experts con-
cerning the investigations carried out on the Sarno-type
landslides in different areas of the Campania Region,
where similar geological settings produced analogous
instabilities. The instabilities were the topic of a large
number of technical reports as well.
A so rich set of scientific papers and documents of-
fers the opportunity to make comparisons not only on
different methodologies adopted in the studies but even
on contrasting results concerning landslide triggering
and propagation mechanisms. In particular, the latter
is crucial for landslide classification. It is also impor-
tant for the definition of the residual risk in the areas
of the Campania Region that have already experienced
landslides, and it provides essential information for the
prediction of future occurrences into areas which have
not previously failed.
Therefore, this is an opportunity to develop a com-
parison between different interpretations developed by
different research groups on a complex natural phe-
nomenon, where the influences of different controls and
triggering factors are overlapped
The paper aims to compare some aspects of the
landsliding described by the authors in several papers
(e.g. d
el
P
Rete
et alii, 1998; f
ioRillo
et alii, 2001;
G
uadaGno
& R
evellino
, 2005) with those of other au-
thors in order to find agreements and disagreementsin
a global and comprehensive picture of the knowledge.
The discussion particularly focuses on landslide
classification aspects, criteria adopted and their real
application. Wide-ranging ambiguities cause uncer-
tainties in applying landslide classification criteria
SOME ASPECTS OF LANDSLIDE CLAS-
SIFICATION
The classification of a natural phenomenon is al-
ways full of difficulties when precisely quantifiable
elements do not subsist. Problems connected to a hier-
archical taxonomy are particularly extensive for land-
background image
THE 1998 SARNO LANDSLIDES: CONFLICTING INTERPRETATIONS OF A NATURAL EVENT
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
73
slides and eroded deposit if water and debris supply
is sufficient and slope is steep enough to accelerate
the whole mass.
C
Ruden
& v
aRnes
(1996) propose a series of limit-
ed modification of the 1978 Varnes’s classification. The
abbreviated classification of flows can be resumed as: i)
Earth flows; ii) Debris flows; iii) Rock flows
H
unGR
et alii (2001) investigate on the ambiguous
aspects existing among the above-mentioned classifi-
cation systems. After re-analysing the main features
of the instabilities, they attain to the description of the
kinematic mechanism of different flow classes. Land-
slide types, which are linked to specific pattern of de-
formation, are defined as: i) Dry (or non liquefied) Sand
(Silt, Gravel, Debris) Flow; ii) Sand (Silt, Debris, Weak
rock) Flow Slide; iii) Clay Flow Slide; iv) Peat Flow; v)
Earth Flow; vi) Debris Flow; vii) Mud Flow; viii) De-
bris Flood; ix) Debris Avalanches; x) Rock Avalanches
It should be noted that debris flows, debris ava-
lanches, earth flows and dry sand flows tend to slide
during the initial failure, subsequently transforming in
a flow-like movement. Differently, some other flows,
such as flow slides, are triggered by initial internal
collapse of the material structure responsible of full or
partial liquefaction of the mass..
It results in different triggering mechanisms
linked to welldefined causes. Sliding failures of a
mass of material imply specific geometric and pore-
pressure conditions of the material; kinematic free-
dom condition may be realized as well.
In addition to the ambiguities pointed out in the
current international landslide classifications, further
troubles are added, in Italy as well as in other coun-
tries, as a consequence of the local translation from
the original terms and of the frequent employment of
obsolete terminologies.
In Italy, the 1978 Varnes’s classification was
translated by C
aRRaRa
et alii (1978). In our opinion,
at that time, the translation was not developed by us-
ing strictly physically-based criteria by which the Var-
nes’s classification was inspired. The Flow class was
translated as Colamento, for the general class, that
literally means “streaming or straining”, and as “Co-
lata”, which is only partly synonym of Flow, for land-
slides occurring in soil. The no use of the term Flow
has added further substantial ambiguities to landslide
descriptions. The term colata (or colamento) inspires
the wrong idea of moisture or saturation of the system.
gineering soils in the v
aRnes
(1978) classification are
scheduled as follow, where landslide phenomena are
discriminated for mechanism, involved material and
velocity: i) Debris flow; ii) Debris avalanche; iii) Mud
flow; iv) Earth flow; v) Rapid Earth flow (usually in sen-
sitive materials); vi) Block streams; vii) Dry sand flow/
dry silt flow; viii) Wet and silt flows; ix) Loess flow.
It is important to note that, v
aRnes
(1978) high-
light that “there is complete gradation from debris
slides to debris flows” and “from debris slides to
debris avalanches”. This remark considerably fol-
lows the initiation model of debris flows proposed by
J
oHnson
& R
ao
(1970) and afterwards reutilized by
Johnson and R
odine
(1984). They define triggering
mechanisms connected to the instability of soil blocks
that can “rotate, jostle, dilate and incorporate water
as they slide”. In an overview, this definition has a lot
of similarity whit the P
ieRson
& C
osta
s
rheological
classification (1987) concerning the transition among
the different types of flows. In v
aRnes
s
classification
(1978), flow slides are reported as sub-aqueous flows
of non-cohesive sand or silt characterised by retro-
gressive mechanism.
H
utCHinson
(1988) classifies flow landslides in
loose material as “debris movements of flow-like form”
distinguishing five main types: i) Mudslides (Earth
Flows of v
aRnes
, 1978); ii) Periglacial mudslides; iii)
Flow slides (distinguished for material types); iv) De-
bris flows (distinguished for material types and envi-
ronment of occurrence); v) Strurzstroms.
H
utCHinson
(1988) restores the term flow slide
used by b
isHoP
et alii (1969) & b
isHoP
(1973) ex-
tending this to describe different phenomena. In the
original definition, a flow slide is typically triggered
by a temporary increase in pore pressure, with con-
sequent decrease in strength. The initial failure is
directly connected to the pore pressure increase in
loose, coarse material. A sudden disturbance causes
the failure that provokes the skeleton destruction, the
decrease of porosity and the liquefaction of the ma-
terial. Usually, the involved slopes are not so deep
and debris consists of waste materials. As regards
debris flows, Hutchison point out that an important
mechanism in their generation is the development of
porewater pressure by repeated undrained loading
associated with their movements. Moreover, debris
flows involving loose or weathered material and as-
sociated to high-intensity rainfall can develop from
background image
F. M. GUADAGNO , P. REVELLINO & G. GRELLE
74
5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
other hand, shows the percentage of the terminology
used in the groups
As shown, the most used macro-classes fall into
the following main landslide types: debris flows,
debris avalanches, mud flows, earth flows and
flowslides. The wide classification range highlights
the difference in the choice of the classification
criteria and, therefore, in the assignment of a cer-
tain landslide type among the authors and research
groups (Tab. 2).
It should be noted that most authors refer to the
well-know classification systems shown above. Conse-
quently, the phenomenon is interpreted in significantly
different ways.
Before the Sarno events, only a few articles had
been published on international journal, but a wealth
of literature in Italian exists. The analysis of this
bibliography leads to a generalized classification (as
colata), even though landslide initiation is well de-
scribed as consisting in initial sliding followed by
fluidification.
THE CLASSIFICATION OD THE SARNO-
TYPE LANDLIDES
As said before, the catastrophic event of the 5-6
of May 1998 inspired a great number of scientific
contributions to the understanding of this type of
landslides.
Further disastrous occurrences followed those of
1998 in Campania (e.g. Cervinara in 1999, Nocera
Inf. in 2005, Ischia island 2006). The similarity of
both mass movement features and geomorphological
environments in which they occur allows the land-
slides to be considered under a common denominator
and the term Sarno-type landslides to be used.
A significant number of scientific papers (about
206) have been, thus, collected in order to compare
both the different classification criteria used to de-
scribe the events and the triggering mechanisms
proposed. Figure 2 shows the article type rate used
for comparison and inserted in the database. Among
them, articles published on international peer review
journals and international conference proceedings
account for more than 62%. Conversely, about the
36% are in Italian, published on national journal or
proceeding; many of them report an English abstract
useful to reconstruct the classification criteria used.
Finally, a very little slice (about 1%) concerns books
and book chapters. It should be noted that in the analy-
sis were not reported the numerous technical reports
supported by research institutions or public bodies,
and the monographs.
As regard the landslide classification and taking
into account the articles published on international
journals and international proceeding only, Table 1
lists the main terms used to categorize the Sarno-
type landslides, grouped according to the affinity of
the material type, of the movement type and of the
order of the cinematic mechanism. Figure 3, on the
Fig. 2 - Type of bibliography collected on the Sarno-type
landslides
Fig. 3 - Classification rate of the Sarno Type-landslide.
The legend correspond to the groups of terms in
Table 1
Tab. 1 - Groups of terms used in the landslide classifica-
tion from international journals and proceedings
background image
THE 1998 SARNO LANDSLIDES: CONFLICTING INTERPRETATIONS OF A NATURAL EVENT
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
75
P
AreSchi
et alii. (2000) report that: "….many
landslides began at the head of the drainage chan-
nels where source areas commonly show a denuded
carbonate substratum; the detachment surface is lo-
cated at the boundary between bedrock and surficial
deposits. The slide scarps often displays a saw-tooth
shape, indicating collapse of the overburden toward
the channel….After failure the material rapidly
evolved into debris flow…
.”
C
Rosta
& d
al
n
eGRo
(2003) describe that: "….
soil slips were triggered and most of them transformed
into debris flows……They scoured the pyroclastic
cover and vegetation along their path, and incorpo-
rated bedrock fragments…More than half of initial
slides are located upslope of morphological discon-
tinuities such as limestone cliffs and roads .... in all
the observed cases failure surface is located within the
pyroclastic cover..
.”
o
livaRes
& P
iCaRelli
(2003) illustrate that: "...
static liquefaction is the fundamental mechanism
that is responsible for flowslide initiation, mostly in
loose granular soils ... infiltration during rainfall can
saturate the cover, leading to soil failure ... flowslide
can ensue if the soil is very loose and susceptible to
static liquefaction....
"
C
alCateRRa
& s
anto
(2004) say that: "…. an ini-
tial small landslide detached from the edge of a path-
way ... This first landslide body has then undergone a
sudden acceleration, with a jump-andfall effect, due
to the presence of a sub- vertical calcareous cliff ...
showing features of a translational slide …. the slope
instability occurred in the upper part of the slope can
be referred to as debris avalanche….. In the middle
portion of the event, the landslide channelized into
a preexisting gully... transformed into an extremely
rapid debris flow
…".
z
anCHetta
et alii. (2004) report that: "... Soil slips
were suddenly transformed into flows ... and moved
downslope. The progressive failure and liquefaction
produced, on rectilinear slopes, a downslope enlarge-
ment ... The progressive enlargement of the failure
area may be explained by undrained loading
...".
The descriptions above show both convergent
and divergent points. Most of authors describe initial
masses which are subject to transformation processes
of fluidification and/or liquefaction. Some others
highlight that the channelling into gullies makes a
progressive dilution of the moving masses which tend
COMPARISONS OF LANDLIDE FEATU-
RES
INITIATION
Generally, landslide initiation is one of the main
aspects in the differentiation of flow-like move-
ments. Different flow types usually show dissimilar
triggering mechanism.
As regards the Sarno-type landslides, the diverse
classifications imply disagreement on the conceptual
model of the instabilities and on the landslide proc-
esses among the different authors. By way of exam-
ple, some descriptions of the landslide events are re-
ported below extracted from articles on international
journals (cf. Tab. 2).
Tab. 2 - Landslide classification from international jour-
nal articles
background image
F. M. GUADAGNO , P. REVELLINO & G. GRELLE
76
5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
to change into hyperconcentrate flows (sensu P
ieRson
& C
osta
, 1987).
The recognition of the mechanism of initial
failure supports the importance of this first stage of
the instabilities as main genetic element in the later
evolution of the phenomenon. In order to better de-
fine this mechanism, some important elements are
reported hereafter.
MAIN GEOLOGICAL ASPECTS
(1) The slope morphology is strongly influenced
by rock structure. The calcareous slopes can be gener-
ally considered as fault and dip slopes whose angles
range from 20-30° (basal zone) to 50-90° (top). The
fault slopes are characterised by irregular surfaces
where one or more natural scarps can be present. The
lower-angled slopes have a more uniform morphol-
ogy, even though faultcontrolled gullies interrupt their
continuity, with many localised dips.
(2) The slopes have been mantled by airfall and
pyroclastic flow deposits of volcanic activity of the
Phlegrean Fields and Somma- Vesuvius Volcanoes.
The pyroclastic sequence is formed by ashy and pumi-
ceous layers alternating with buried horizons of soil.
They dip at angles similar to those of the bedrock sur-
face. The thickness increases from the top of the slope
(0.5-2 m) to the foot of the hill (over 10 m).
(3) Therefore, the sequences of pyroclastic lay-
ers and soil horizons consist of discontinuous layers
with varying geotechnical properties. Pumice should
be considered as a graded granular material while soil
horizons as cohesive materials. In the pumice layers,
the presence of interconnected capillary-size voids
within the grains influences water flow circulation,
causing suction phenomena and complex water diffu-
sion. Owing to the retention capacity of the pumice,
a greater volume of water is needed to obtain fully
saturated conditions than that necessary for soils made
of non-porous clasts (e
sPosito
& G
uadaGno
, 1998).
(4) The presence of allophane minerals with some
organic matter in the horizons determines specific
geotechnical characteristics in the materials. There are
problems connected with soil testing, where a special
methodology must be used (G
uadaGno
& m
aGaldi
,
2000). Generally, these soils exhibit high values of
liquid limit at relatively low clay contents. The resid-
ual friction angle is generally high (close to 30°), and
comparable to the peak angle.
(5) As expected, layers and horizons of soil exhib-
it extremely variable permeability. The pumice layers
can act as drain layers, while the clayey horizons are
quasi-impervious. In such a hydrogeological setting,
any geometrical modifications can provoke important
changes in the ground water flow pattern.
(6) The granulometric characteristics of the ma-
trix of debris flow deposits range from silty sand with
gravel and sand with silt and gravel. A large amount of
limestone clasts is also present. Calcareous boulders
(up to 2 m in diameter) as well as trees or anthropo-
genic elements were observed in the depositional area
(7) Finally, slope micro-morphology, considered
as local geomorphological setting, plays a decisive
role in locating the source of the instabilities and in
controlling the development of the phenomena..
SOME EVIDENCES
In our opinion, there are some unequivocal evi-
dences describing the event in its first stage. They can
be listed as follows.
(1) Mass detachments occur in specific slope
points involving sometimes very limited volumes
(few cubic metres). As reported by many authors,
these points correspond to edges of natural scarps
(Fig. 4). In some cases, the first movement can be
related to rock fall down the scarp. The presence of
more scarps prevents retrogressive movements. More
extensive instabilities take place in correspondence of
man-made cuts (Fig. 5).
(2) The source areas exhibit the typical morpho-
logical characters of translational slides. In the source
Fig. 4 - Debris avalanches and debris flows of Ischia
Island on 30th April 2006. Source areas are
located in correspondence of a natural scarp
background image
THE 1998 SARNO LANDSLIDES: CONFLICTING INTERPRETATIONS OF A NATURAL EVENT
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
77
posing factors and those triggering the landslide from
a propositional viewpoint rather than descriptive only.
As far as we said, it is possible to define a theoreti-
cal model of the initial instabilities and of the subse-
quent evolution.
the initial instabilities and of the subsequent evo-
lution. There are no doubt that the initial movement
consists in the failure of relatively coherent slabs of
pyroclastics in the highest parts of the slope. The
slabs slide on failure surfaces, usually located within
the pyroclastic sequence. The plastic behaviour of
the initial sliding mass is proven by tensional cracks
present on some sites where the landsliding process
was aborted and by the fact that many initial slides oc-
cur in the back-slope of trackways and natural scarps.
Increase of pore pressure within the pyroclastic cover
should be considered as the more likely mechanism in
triggering the failures.
The mobilised mass of the initial failure gener-
ally impacts on downslope deposits where liquefac-
tion phenomena, by means of rapid undrained loading
(J
oHnson
, 1984), could be triggered. In nearly all cas-
es the initial slides transformed into extremely rapid
flows, growing substantially in volume by incorporat-
ing materials and surface water.
According to the v
aRnes
'
s
classification (1978)
these landslides can be classified as debris avalanches
and debris flows; by applying the criteria of C
Ruden
& v
aRnes
(1996) as complex landslide, debris slide/
debris flow, from very rapid to extremely rapid and
high water content; hillslope debris flows and de-
bris flows if we use the classification of Hutchinson
(1988). Moreover, these landslide mechanisms can be
compared to those described by H
unGR
et alii (2001),
as debris avalanches, phenomena that involve open
slopes and therefore are typically not confined in gul-
lies, at least in their initial stages.
In the case of the Campania landslides, many de-
bris avalanches can became confined in gullies in mid-
dle or lower portions of the slope, transforming into
debris flows, still eroding the pyroclastic and colluvial
cover from the slope. At the base of the slopes, the
flows spread out in thin depositional fans. Deposition
generally occurs in the basal plain where the veloci-
ties decrease. If large amounts of water are present in
the area or in the gullies, the landslide material can be
reworked by hyper-concentrated flows.
Finally, the analysis carried out on the wide bibli-
area, the slope should be considered as open slope and
the trigger is independent from the presence of well-
defined drainage lines.
(3) The location of the sliding surface, within the
pyroclastic sequence or at the contact with the bed-
rock, is an area of disagreement. Actually, field ob-
servations demonstrate that a large part of the initial
failure surfaces are generally located in the pyroclastic
multilayer cover and often highlight the presence of
clayey deposits at the base.
(4) In the upper part of the slopes, before becom-
ing channelled, landslides displayed a triangular shape
in plan, this being a typical characteristic of many de-
bris avalanches and related to the progressive entrain-
ment of material downslope. Field survey also show
that gullies are lacking of material.
(5) An important aspect is related to the very
high velocities of the flows. The cleaned gullies, tilt-
ing along channel bends, lateral deposit, high impact
energies, and other numerous evidences highlight top-
down mechanism.
DISCUSSION AND CONCLUDING RE-
MARKS
If the same landslide phenomenon is classified in
different ways, it is plain that the discriminating crite-
ria for its classification are not clear or they show areas
of uncertainty. Therefore, there is the need to have at
disposal a classification system that leaves no doubts
and describing the landslide mechanism in terms of
susceptibility and hazard assessments too. Landslides
described in the various classification systems pro-
pose different trigger mechanisms, but it should be
particularly important ascertain what are the predis-
Fig. 5 - Debris avalanche at Nocera Inferiore on 4
th
March
2005. Road cuts at the source area location are
also shown
background image
F. M. GUADAGNO , P. REVELLINO & G. GRELLE
78
5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
for mitigation strategies, and preventing distortion of
the general terms due to national and local effects.
ography after the 1998 landslide events has pointed out
the need to redefine the correct nomenclature of flow-
like landslides, taking into account the practical effect
REFERENCES
b
aRbaRella
m. & G
oRdini
C. (2006) - kinematic GPS survey as validation of LIDAR strips accuracy. Annals of Geophysics
49, 1: 21-23
b
ilotta
e., C
asCini
l., f
oResta
v. & s
oRbino
G. (2005) - Geotechnical characterization of pyroclastic involved in huge
flowslides. Geotechnical and Geological Engineering, 23(4): 365-402
b
isson
, m., P
aResCHi
, m.t., z
anCHetta
, G., s
ulPizio
, R. & s
antaCRoCe
, R. (2007) - Volcaniclastic debris-flow occurrences in the
Campania region (Southern Italy) and their relation to Holocene - Late Pleistocene pyroclastic fall deposits: Implications
for large-scale hazard mapping. Bulletin of Volcanology, 70(2): 157-167.
b
udetta
P. (2002) - Risk assessment from debris flows in pyroclastic deposits along a motorway, Italy. Bull. Eng. Geol. Env.,
61: 293-301.
b
udetta
P. (2010) - Rockfall-induced impact force causing a debris flow on a volcanoclastic soil slope: A case study in southern
Italy. Natural Hazards and Earth System Science 10(9): 1995-2006
b
udetta
P. &
de
R
iso
R. (2004) - The mobility of some debris flows in pyroclastic deposits of the northwestern Campanian region
(southern Italy). Bulletin of Engineering Geology and the Environment, 63(4): 293-302.
b
aRbaRella
m. & G
oRdini
C. (2006) - kinematic GPS survey as validation of LIDAR strips accuracy. Annals of Geophysics
49, 1: 21-23.
b
ilotta
e., C
asCini
l., f
oResta
v. & s
oRbino
G. (2005) - Geotechnical characterization of pyroclastic involved in huge
flowslides. Geotechnical and Geological Engineering, 23(4): 365-402.
b
isson
, m., P
aResCHi
, m.t., z
anCHetta
, G., s
ulPizio
, R. & s
antaCRoCe
, R. (2007) - Volcaniclastic debris-flow occurrences in the
Campania region (Southern Italy) and their relation to Holocene - Late Pleistocene pyroclastic fall deposits: Implications
for large-scale hazard mapping
. Bulletin of Volcanology, 70(2): 157-167.
b
udetta
P. (2002) - Risk assessment from debris flows in pyroclastic deposits along a motorway, Italy. Bull. Eng. Geol. Env.,
61: 293-301.
b
udetta
P. (2010) - Rockfall-induced impact force causing a debris flow on a volcanoclastic soil slope: A case study in southern
Italy. Natural Hazards and Earth System Science, 10(9): 1995-2006.
b
udetta
P. &
de
R
iso
R. (2004) - The mobility of some debris flows in pyroclastic deposits of the northwestern Campanian region
(southern Italy). Bulletin of Engineering Geology and the Environment, 63(4): 293-302.
C
alCateRRa
d. & s
anto
a. (2004) - The January 10, 1997 Pozzano landslide, Sorrento Peninsula, Italy. Engineering Geology,
75: 181-200.
C
alCateRRa
d., P
aRise
m. & P
alma
b. (2003) - Combining historical and geological data for the assessment of the landslide
hazard: A case study from Campania, Italy. Natural Hazards and Earth System Science, 3 (1-2): 3-16.
C
asCini
l. (2004) - The flowslides of May 1998 in the Campania region, Italy: the scientific emergency management. Rivista
Italiana di Geotecnica, 2: 11-44.
C
asCini
l., C
uomo
s., s
oRbino
G. (2005) - Flow-like mass movements in pyroclastic soils: remarks on the modelling of triggering
mechanisms. Rivista Italiana di Geotecnica, 4: 11-31.
C
Hiessi
, v., d'o
RefiCe
, m., s
uPeRbo
, s. (2003) - Geophysical surveying of slopes affected by debris flows: The case of S. Felice
a Cancello (Caserta, Southern Italy). Annals of Geophysics, 46(6): 1283-1295.
C
oates
, d. R. (1977) - Landslide prospectives. In: Landslides (C
oates
d.R., e
d
.) Geological Society of America: 3-38.
C
Rosta
G.b. & d
al
n
eGRo
P. (2003) - Observations and modelling of soil slip - debris flow initiation processes in pyroclastic
deposits: the Sarno 1998 event. Natural Hazards and Earth System Sciences, 3 (1): 53-69
C
Ruden
d.m. & v
aRnes
d.J. (1996) - Landslide types and processes. In: t
uRneR
a.k.; s
HusteR
R.l. (
eds
) Landslides: Investiga-
tion and Mitigation. Transp Res Board, Spec Rep 247: 36-75.
d'a
mbRosio
d., d
i
G
ReGoRio
s. & i
ovine
G. (2003) - Simulating debris flows through a hexagonal cellular automata model:
SCIDDICA S. Natural Hazards and Earth System Science, 3(6): 545-559.
background image
THE 1998 SARNO LANDSLIDES: CONFLICTING INTERPRETATIONS OF A NATURAL EVENT
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
79
d'a
mbRosio
d., s
PataRo
w. & i
ovine
G. (2006) - Parallel genetic algorithms for optimising cellular automata models of natural
complex phenomena: An application to debris flows. Computers and Geosciences, 32(7): 861-875.
d'a
mbRosio
d., i
ovine
G., s
PataRo
w. & m
iyamoto
, H. (2007) - A macroscopic collisional model for debris-flows simulation.
Environmental Modelling and Software, 22(10): 1417-1436.
d'a
mbRosio
d., d
i
G
ReGoRio
s., i
ovine
G., l
uPiano
v., R
onGo
R. & s
PataRo
w. (2003) - First simulations of the Sarno debris
flows through Cellular Automata modelling. Geomorphology, 54: 91-117
d'a
mbRosio
, d., d
i
G
ReGoRio
, s., i
ovine
, G., l
uPiano
, v., m
eRenda
, l., R
onGo
, R. & s
PataRo
, w. (2002) - Simulating the Curti-
Sarno debris flow through cellular automata: The model SCIDDICA (release S2). Physics and Chemistry of the Earth 27
(36):
1577-1585.
d
amiano
e. & o
livaRes
l (2010) - The role of infiltration processes in steep slope stability of pyroclastic granular soil: labora-
tory and numerical investigation. Natural Hazards, 52: 329-350.
d
e
v
ita
P. & P
isCoPo
v. (2002) - Influences of hydrological and hydrogeological conditions on debris flows in pri-vesuvian
hillslopes. Natural Hazards and Earth System Sciences, 2, 27-35.
d
e
v
ita
, P., a
GRello
, d. & a
mbRosino
, f. (2006) - Landslide susceptibility assessment in ash-fall pyroclastic deposits surround-
ing Mount Somma- Vesuvius: Application of geophysical surveys for soil thickness mapping. Journal of Applied Geophysics,
59
(2): 126-139.
d
e
v
ita
P., C
eliCo
P., s
inisCalCHi
m. & P
anza
R. (2006) - Distribuzione, caratteri idrogeologici e suscettibilità a franare delle
coltri piroclastiche sui versanti carbonatici peri-vesuviani (Italia). Italian Journal of Engineering Geology and Environ-
ment, 1: 75-98.
d
e
v
ita
P, d
i
C
lemente
e, R
olandi
m & C
eliCo
P (2007) - Engineering Geological Models Of The Initial Landslides Occurred
On The April 30th, 2006, At The Mount Di Vezzi (Ischia Island, Italy). Italian Journal of Engineering Geology and Environ-
ment, 2
d
el
P
Rete
m., G
uadaGno
f.m. & H
awkins
a.b. (1998) - Preliminary report on the landslides of 5 May 1998, Campania, south-
ern Italy. Bull. Eng. Geol. Env., 57: 113-129.
d
i
C
ResCenzo
G., s
anto
a. (2005) - Debris slides-rapid earth flows in the carbonate massifs of the Campania region (Southern
Italy): Morphological and morphometric data for evaluating triggering susceptibility. Geomorphology, 66: 255-276
d
i
C
ResCenzo
G., d
e
f
alCo
m.,i
eRvolino
v.e., R
inaldi
s., s
antanGelo
n. & s
anto
a. (2008) - Proposta di un nuovo metodo
semiquantitativo per la valutazione della suscettibilità all’innesco di colate rapide di fango nei contesti carbonatici della
Campania
. It. J. Eng. Geol. and Env, 1
d
i
m
aio
R., P
ieGaRi
e, s
CotellaRo
& s
oldovieRi
mG (2007) - Resistivity tomographies to define thickness and water content of
pyroclastic covers at Mt. di Vezzi (Ischia island, Italy). Italian Journal of Engineering Geology and Environment, 2
e
sPosito
l. & G
uadaGno
f.m. (1998) - Some special geotechnical properties of pumice deposits. Bullettin of Eng. Geol. Env.,
57: 1-10.
f
ioRillo
f. & w
ilson
R.C. (2004) - Rainfall induced debris flows in pyroclastic deposits, Campania (southern Italy). Eng. Geol.,
75: 263-289
f
ioRillo
f., G
uadaGno
f.m., a
Quino
s. & d
e
b
lasio
a. (2001) - The December 1999 Cervinara landslides: further debris flows
in the pyroclastic deposits of Campania (southern Italy). Bull. Eng. Geol. Env., 60: 171-184.
f
Rattini
P., C
Rosta
G.b., f
usi
n. & d
al
n
eGRo
P. (2004) - Shallow landslides in pyroclastic soils: a distributed modelling ap-
proach for hazard assessment. Engineering Geology, 73: 277-295.
G
ReCo
R., G
uida
a., d
amiano
e. & o
livaRes
l. (2010) - Soil water content and suction monitoring in model slopes for shallow
flowslides early warning applications. Physics and Chemistry of the Earth, 35(3-5): 127-136
G
uadaGno
f.m. (2000) - The landslides of 5 May 1998 in Campania, Southern Italy: are they natural disaster or also man-
induced phenomena? Journal of Nepal Geological Society, 22: 463-470.
G
uadaGno
f.m. & R
evellino
P. (2005) - Debris avalanches and debris flows of the Campania Region (Southern Italy). In:
Debris-Flow Hazards and Related Phenomena J
akob
m. & H
unGR
o. (
eds
.), Springer and Praxis editorials. ISBN: 978-3-
540-20726-9.
G
uadaGno
f.m., m
aRtino
s. & s
CaRasCia
m
uGnozza
G. (2003) - Influence of man-made cuts on the stability of pyroclastic cov-
ers (Campania - Southern Italy): a numerical modelling approach. Environmental Geology, 43: 371-384.
background image
F. M. GUADAGNO , P. REVELLINO & G. GRELLE
80
5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
G
uadaGno
f.m., C
eliCo
P.b., e
sPosito
l., P
eRRiello
z
amPelli
s. & s
CaRasCia
m
uGnozza
G. (1999) - The Debris Flows of 5-6
May 1998 in Campania, Southern Italy. Landslide News, 12: 5-7.
G
uadaGno
f.m., f
oRte
R., R
evellino
P., f
ioRillo
f., f
oCaReta
m. (2005) - Some aspects of the initiation of debris avalanches
in the Campania region: the role of morphological slope discontinuities and the development of failure. Geomorphology,
66: 237-254.
H
ansen
m. (1984) - Strategies for classification of landslides. Slope Instability. New York: J.Wiley & Sons: 1-23.
H
utCHinson
, J. n. (1988). General Report: Morphological and geotechnical parameters of landslides in relation to geology and
hydrogeology. Proceedings, Fifth International Symposium on Landslides (e
d
: b
onnaRd
C.), 1, 3-35. Rotterdam: Balkema
H
unGR
o., e
vans
s.G., b
ovis
m. & H
utCHinson
J.n. (2001) - Review of the classification of landslides of the flow type. Env.
Eng. Geo. 7(3): 1-18.
i
ovine
G., d'a
mbRosio
d. & d
i
G
ReGoRio
s. (2005) - Applying genetic algorithms for calibrating a hexagonal cellular automata
model for the simulation of debris flows characterised by strong inertial effects. Geomorphology, 66: 287-303.
i
ovine
G., d
i
G
ReGoRio
s. & l
uPiano
v. (2003) - Debris-flow susceptibility assessment through cellular automata modeling: An
example from 15-16 December 1999 disaster at Cervinara and S Martino Valle Caudina (Campania, southern Italy). Nat.
Haz. E. Syst. Sc. 3, 5: 457-468.
J
oHnson
a.m. & R
odine
J.R. (1984) - Debris flow. In b
Runsden
, & P
RioR
(
eds
), Slope instability: New York: John Wiley & Sons,
257-361.
i
ovino
m. & P
eRRiello
z
amPelli
s. (2007) - The April 30th, 2006, Mt.Vezzi Landslides (Ischia Island, Italy) in the context of the
sliding susceptibility of volcanic soils in Campania. Italian Journal of Engineering Geology and Environment, 2
m
azzaRella
a. & d
iodato
n. (2002) - The alluvial events in the last two centuries at Sarno, southern Italy: their classification
and power-law timeoccurrence. Theoretical and Applied Climatology, 72: 75-84
o
livaRes
l. & d
amiano
e. (2007) - Post-failure mechanics of landslides: a laboratory investigation of flowslides in pyroclastic
soils. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 133(1): 51–62.
o
livaRes
l. & P
iCaRelli
l. (2003) - Shallow flowslides triggered by intense rainfalls on natural slopes covered by loose unsatu-
rated pyroclastic soils Géotechnique, 53(2): 283-288.
o
Ramas
d
oRta
d., t
oyos
G., o
PPenHeimeR
C., P
aResCHi
m.t., s
ulPizio
R. & z
anCHetta
, G. (2007) Empirical modelling of the
May 1998 small debris flows in Sarno (Italy) using LAHARZ. Natural Hazards. 40(2): 381-396.
P
aResCHi
m.t., s
antaCRoCe
R., s
ulPizio
R. & z
anCHetta
G. (2002) - Volcaniclastic debris flows in the Clanio Valley (Campania,
Italy): insights for the assessment of hazard potential. Geomorphology, 43: 219-231.
P
aResCHi
m.t., f
avalli
m., G
iannini
f., s
ulPizio
R., z
anCHetta
G. & s
antaCRoCe
R. (2000) - May 5, 1998, debris flows in
circum-Vesuvian areas (southern Italy): Insights for hazard assessment. Geology, 28(7): 639-642.
P
eRRiello
z
amPelli
,s. (2009) - Evaluation of sliding susceptibility in volcaniclastic soils of campania (southern Italy) aided by
GIS techniques Geografia Fisica e Dinamica Quaternaria, 32(2): 227-236.
P
astoR
m., H
addad
b., s
oRbino
G., C
uomo
s. & d
RemPetiC
v (2009) - A depth-integrated, coupled SPH model for flow-like
landslides and related phenomena. International Journal for Numerical and Analytical Methods in Geomechanics, 33(2):
143-172
P
iCaRelli
l., o
livaRes
l. & a
volio
b. (2008) - Zoning for flowslide and debris flow in pyroclastic soils of Campania Region
based on “infinite slope” analysis. Engineering Geology 102: 132-141.
P
iCaRelli
l., o
livaRes
l., C
omeGna
l. & d
amiano
e. (2008) - Mechanical aspects of flowlike movements in granular and fine
grained soils. Rock Mechanics and Rock Engineering 41(1): 179-197.
P
ieRson
t.C. & C
osta
J.e. (1987). - A rheological classification of sub-aerial sediment-water flows. Geol. Soc. Am. Rev. Eng.
Geol. 7: 1-12.
R
evellino
P., G
uadaGno
f. m. & H
unGR
o. (2008) - Morphological methods and dynamic modelling in landslide hazard assess-
ment of the Campania Apennine carbonate slope. Landslides, 5: 59-70.
R
evellino
P., H
unGR
o., G
uadaGno
f.m. & e
vans
s.G. (2004) - Velocity and runout simulation of destructive debris avalanches
in pyroclastic deposits, Campania Region, Italy. Environmental Geology, 45: 295-311.
s
iRanGelo
b. & b
RaCa
G. (2004) - Identification of hazard conditions for mudflow occurrence by hydrological model Application
of FLaIR model to Sarno warning system. Engineering Geology, 73: 267-276
background image
THE 1998 SARNO LANDSLIDES: CONFLICTING INTERPRETATIONS OF A NATURAL EVENT
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
81
s
Cotto
di
s
antolo
& e
vanGelista
a. (2009) - Some observations on the prediction of the dynamic parameters of debris flows in
pyroclastic deposits in the Campania region of Italy. Nat Hazards 50: 605-622.
s
oRbino
G., s
iCa
, C. & C
asCini
l. (2010) - Susceptibility analysis of shallow landslides source areas using physically based
models. Nat. Haz., 53(2): 313-332.
t
oyos
G., G
unasekeRa
R., z
anCHetta
G., o
PPenHeimeR
C., s
ulPizio
R., f
avalli
m. & P
aResCHi
m.t. (2008) - GIS-assisted model-
ling for debris flow hazard assessment based on the events of May 1998 in the area of Sarno, Southern Italy: II. Velocity and
dynamic pressure. Earth Surface Processes and Landforms 33(11): 1693-1708
v
aRnes
d.J. (1978) - Slope movement types and processes. In: s
CHusteR
R. l. & k
Rizek
R. J. e
d
., Landslides, analysis and
control. Transportation Research Board Sp. Rep. No. 176, Nat. Acad. oi Sciences: 11–33
v
inGiani
s. & t
eRRibile
f. (2007) - Soils of the detachment crowns of Ischia landslides (Italy). It. J. Eng. Geol. and Env., 2.
z
anCHetta
R. s
ulPizio
m.t. P
aResCHi
f.m. l
eoni
R. & s
antaCRoCe
(2004) - Characteristics of May 5-6, 1998 volcaniclastic
debris flows in the Sarno area (Campania, southern Italy): relationships to structural damage and hazard zonation . Journal
of Volcanology and Geothermal Research, 133(377-393): 293-302.
Statistics