Mapping landslide susceptibility through physically-based modeling
Federica Angela MevoliL. BorselliMichele SantangeloAngelo UgentiDaniela De LuciaNunzio Luciano FazioMauro Rossi
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Landslide susceptibility is the likelihood of a landslide occurring in a specific area based on the local terrain conditions. Susceptibility does not take into account the size, duration, or frequency of occurrence of landslides. Different approaches and methods have been proposed to determine the likelihood of occurrence of landslides: geomorphological mapping, analysis of landslide inventories, heuristic terrain zoning, statistically-based classifications and physically based numerical modelling (Aleotti and Chowdhury, 1999; Guzzetti et al., 1999). The last two approaches are preferred for assessing susceptibility in quantitative terms. Today, statistically based methods are preferred for small-scale landslide susceptibility zonations. Performing this task by using physically-based approaches is more challenging, as the performance of numerical analyses usually requires detailed geomechanical and hydrological data, whose collection demands significant time and costly efforts.However, this work is primarily motivated by the following question: Can landslide susceptibility maps at smaller scales than detail-scale truly not be attained through the application of physically-based approaches?The authors show their first attempt in answering the question through the combined application of Geographic Information Systems (GIS) and a 2.5D Limit Equilibrium Method (LEM) implemented using the SSAP software (Borselli, 2023). The results obtained in a study area in Southern Italy and the physically-based landslide susceptibility map derived at basin-scale are presented and discussed. This preliminary but yet reproducible analysis allows to drive future efforts in physically-based susceptibility zonation. ReferencesAleotti, P., & Chowdhury, R. (1999). Landslide hazard assessment: summary review and new perspectives. Bulletin of Engineering Geology and the environment, 58, 21-44. DOI: https://doi.org/10.1007/s100640050066Borselli L. (2023). "SSAP 5.2 - slope stability analysis program". Manuale di riferimento. Del codice ssap versione 5.2. Researchgate.   DOI: https://dx.doi.org/10.13140/RG.2.2.19931.03361Guzzetti, F., Carrara, A., Cardinali, M., & Reichenbach, P. (1999). Landslide hazard evaluation: a review of current techniques and their application in a multi-scale study, Central Italy. Geomorphology, 31(1-4), 181-216. DOI: https://doi.org/10.1016/S0169-555X(99)00078-Every year, especially in the rainy season, landslides occur quite often in Lao Cai – a northern mountainous province of Vietnam. Specifically, in the year 2019, several landslides were observed to occur near the Sapa Ancient Rock Field in Hau Thao commune, Sapa town, Lao Cai province. In December 2019, a landslide investigation was conducted to examine the mechanism and possible causes of the landslides. Besides that, as the landslide distribution in this area is still unclear, this study will also aim to show the landslide denseness in a 700 m × 700 m square map as well as survey results in 2019 of two main landslides in such map. According to the survey, the landslide is the main phenomenon of geomorphological development in this area, being a combination of multiple different landslides with varying sizes and dissimilar triggers. The first survey landslide is about 50 m wide and 350 m long and has still been going on in recent years, with annual horizontal displacement being around 0.8 m. Meanwhile, the second one is a typical flash-landslide caused by rainfall. Despite being quite small in scale, about 15 m × 40 m, its characteristics indicate a dangerous implication in the future. This information will be the basis for further ongoing studies.
Field survey
Landslide mitigation
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Bedrock
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On the basis of comprehensive geological environment investigations,this article studies morphological characteristics,distribution and stability of landslide 1,landslide 2,and landslide 3 at the Teng high school.Transfer coefficient method and Morgenstern-Price method are used in calculation of stability of the landslides.Finally there is a comprehensive evaluation on the stability of the landslides.The result shows:(1)Landslide area that happened in landslide 1,landslide 2,and landslide 3 slid and resulted in the unique retrogressive landslide.(2) landslide 2 is basically stable in dry level and under-stable in normal level and flood level;landslide 1 and landslide 3 are stable under any condition.
Landslide mitigation
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Abstract Emplacement of submarine landslides, or mass‐transport deposits, can radically reshape the physiography of continental margins, and strongly influence subsequent sedimentary processes and dispersal patterns. Typically, progressive healing of the complicated relief generated by the submarine landslide occurs prior to progradation of sedimentary systems. However, subsurface and seabed examples show that submarine channels can incise directly into submarine landslides. Here, the evolution of a unique exhumed example of two adjacent, and partially contemporaneous, submarine channel‐fills is documented. The channels show deep incision (>75 m), and steep lateral margins (up to 70°), cut into a >200 m thick submarine landslide. The stepped basal erosion surface, and multiple terrace surfaces, are mantled by clasts (gravels to cobbles) reflecting periods of bedload‐derived sedimentation, punctuated by phases of downcutting and sediment bypass. The formation of multiple terrace surfaces in a low aspect ratio confinement is consistent with the episodic migration of knickpoints during entrenchment on the dip slope of the underlying submarine landslide. Overlying sandstone‐rich channel‐fills mark a change to aggradation. Laterally stacked channel bodies coincide with steps in the original large‐scale erosion surface, recording widening of the conduit; this is followed by tabular, highly aggradational fill. The upper fill, above a younger erosional surface, shows an abrupt change to partially confined tabular sandstones with normally graded caps, interpreted as lobe fringe deposits, which formed due to down‐dip confinement, followed by prograding lobe deposits. Overlying this, an up‐dip avulsion induced lobe switching and back‐stepping, and subsequent failure of a sandstone body up‐dip led to emplacement of a sandstone‐rich submarine landslide within the conduit. Collectively, this outcrop represents episodic knickpoint‐generated incision, and later infill, of a slope adjusting to equilibrium. The depositional signature of knickpoints is very different from existing models, but is probably reflective of other highly erosional settings undergoing large‐scale slope adjustment.
Submarine landslide
Aggradation
Turbidity current
Mass wasting
Progradation
Passive margin
Terrace (agriculture)
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This paper sets out to study the spatial distribution of international migrants in the City of Buenos Aires through a statistical and cartographic analysis based on the information collected by the 2010 National Population, Homes and Living Conditions Census. A socio-spatial analysis is carried out of the Census data, which are georeferenced using Geographic Information Systems (GIS). This work is done through thematic mapping and spatial distribution statistical index calculations. Thus, from a quantitative methodological perspective combining a macro-social (as it involves the whole city) and a micro-spatial (as it allows for the visualization of differences caused on an intra-urban level) scale, what is analyzed is how these groups’ urban presence, which results from various social and spatial trajectories, is evidenced in specific localization patterns within the urban territory
Georeference
Thematic map
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The leptospirosis, one of the most prevalent zoonosis in the world, is endemic in
Brazil. In urban areas it occurs, characteristically, after periods of high pluviosity with
flooding. The city of Rio de Janeiro presented, in 1996, one of the largest urban
epidemics, just after big storms that happened in February, with 1792 notified cases and
51 deaths. The aim of this dissertation is to describe the space-time pattern of
leptospirosis, and, at the same time, to evaluate a techniques for detection of clusters of
cases and delimitation of risk surfaces, contributing to develop methods for
environmental surveillance with a territorial approach.
In the first paper, an exploratory technique of spatial analysis was used, based on
the ratio between two layers, allowing the visualisation of the risk surface of the disease.
The interpolation method for the creation of the layers was a intensity Kernel of the
points representing the place of residence of the cases, in the numerator, and a Kernel of
the population of the census tracts in the denominator. Through this method it was
possible to delimit “hot” areas, and to compare them, visually, with the maps of the
demographic density, of slums and the polygons that delimit areas subject to floods.
Comparing the epidemic year (1996) with the other ones, it was noticed that the largest
incidence rates were not observed in supposed “higher risk” areas.
In the second paper we present a space-time analysis of leptospirosis cases in the
city of Rio de Janeiro, between 1995 and 1999, using a method for detection and
localisation of space-time clusters, based on a scan statistics, available in the software
SaTScan. Clusters were detected only in the epidemic year of 1996. The main cluster
was localised in Jacarepagua and the others were spread throughout the entire city,
expressing the intensity of the epidemic on this year. Differences in the profile of the
cases in the two moments – epidemic and endemic – were significant (qui-square test)
only for the variables severity of disease and gender. Endemic cases were more severe,
and the absolute number of women was significantly larger in the epidemic period.
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Landslide RS survey includes the landslide recognition, the collection of the basic information, and the spatial analysis. With the Tiantaixiang landslide RS as an example, this paper illustrates the utilization of “special points” to determine the boundary and influence zone, movement characteristics and scale of the landslide. Landslide RS monitoring can be divided into direct RS monitoring and indirect RS monitoring. It is difficult to determine the exact time for large scale high velocity landslide movement, the scale of landslide movement is relatively small compared with the resolution of the satellite image, and as RS data are discontinuous and rather expensive, they are not quite suitable for RS direct landslide monitoring. Indirect monitoring means monitoring the environmental change caused by landslide activities. The Yigong landslide RS serves as another example to illustrate RS monitoring of lake change, ecological destruction and new landslides caused by landslide dam burst.Landslide RS evaluation means the evaluation of the stability, the prediction of the future activities, the detection of the affecting factors and the evaluation of the regional hazards caused by landslide development. Tiantaixiang and Qianjiangpin landslides and regional landslides in the Three Gorge area all serve as examples.
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The Oak Ridges Moraine in southern Ontario is a poly- genetic moraine constructed of a number of coalesced deposits of gla- cifluvial and glacilacustrine origin. A detailed study of the facies ar- chitecture has been completed on a series of pit sections extending ; 300 m subparallel to the paleoflow direction. Eight major lithofacies and five facies associations have been described. These data have been interpreted to be upper-flow-regime hyperconcentrated-flood-flow de- posits emplaced under a regime of rapid flow expansion and loss of transport capacity within a plane-wall jet with an associated hydraulic jump. Deposition from the plane-wall jet with jump occurred in three zones of flow transformation: zone of flow establishment, transition zone, and zone of established flow. Massive gravels with unconsolidated sand intraclasts and open-work gravel / gravel-sand couplets were de- posited in the zone of flow establishment by hyperconcentrated and supercritical flows, respectively. Immediately downflow low-angle cross-stratified sand incised by steep-walled scours infilled by diffusely graded sand define the transition zone, the zone of maximum vortex erosion, and the distal limit of deposits emplaced under upper-flow- regime conditions. These strata record rapid bed aggradation from sediment-laden supercritical flows that episodically were scoured by large vortices generated within migrating hydraulic jumps. Strati- graphically upward and downflow strata consist only of lower-flow- regime sedimentary structures. Medium-scale, planar cross-strata and small-scale cross-lamination related to migrating 2-D dunes and cur- rent ripples, respectively, characterize the zone of established flow. The facies and sediment architecture suggest that this fan was deposited during a relatively short period of time (days, weeks) by energetic sed- iment-laden floods.
Hyperconcentrated flow
Hydraulic jump
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Caldera
Alluvial fan
Bedrock
Aggradation
Landform
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