full-text - Donnarumma et al. 2013 - Slope Angle as Indicator Parameter of Landslide Susceptibility in a Geologically Complex Area (original) (raw)
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Statistical Analysis of Landslide Susceptibility, Macerata Province (Central Italy)
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Every year, institutions spend a large amount of resources to solve emergencies generated by hydrogeological instability. The identification of areas potentially subject to hydrogeological risks could allow for more effective prevention. Therefore, the main aim of this research was to assess the susceptibility of territories where no instability phenomena have ever been detected. In order to obtain this type of result, statistical assessments of the problem cannot be ignored. In this case, it was chosen to analyse the susceptibility to landslide using a flexible method that is attracting great interest in the international scientific community, namely the Weight of Evidence (WoE). This model-building procedure, for calculating landslide susceptibility, used Geographic Information Systems (GIS) software by means of mathematical operations between rasters and took into account parameters such as geology, acclivity, land use, average annual precipitation and extreme precipitation event...
2003 Seattle Annual Meeting, 2003
The aim of present work is the assessment and mapping of landslide susceptibility in a test area located in Cilento National Park (more precisely in Caselle in Pittari, situated in Campania, a region in Southern Italy). From the geologic point of view, this area of study is characterized by the outcrop of two stratigraphic-structural units, both deformed during Alpine orogenesis: the Alburno-Cervati unit (cretaceous), resulted from deformation of the central portion of the Campano-Lucanian carbonate platform, and the North-Calabrian unit (cenozoic) resulted from the deformation of sin-orogenic basin. The first unit is constituted by limestone formations and the second one by clayey, sandy, carbonate flysch. We studied the distribution and the characterization of landslides in the study area through photointerpretation and geomorphologic survey. This research shows that in the above mentioned area there are two types of landslides: slow earth flow and rock falls. Slow earth flow are numerous in the flysch formations and their landslide masses are quite large. Rock falls occur in limestone formations. They are less frequent and do not reach vast proportions. GIS-based techniques are the best approach to the study of landslide susceptibility because they allow the management of several themes concerning instability factors. Besides, morphometric characteristics, playing an important role in landsliding processes, can be determined through the analysis of the digital terrain model. Here follows a list of the main phases of our analysis focusing on the mapping of earth flow susceptibility: -selection of the most useful instability factors (i.e.: lithology, slope, land use, hydrography, etc.); -multivariate statistic analysis of the selected factors in landslide areas; -creation of a model of susceptibility; -mapping of landslide susceptibility; -testing phase. This method is based on the concept that instability factors in susceptible areas are similar to those observed in areas in which landslides have already happened. The application of this method would be useful to locate potential unstable areas, and so to predict the occurrence of future landslides.
Landslide hazard assessment in the Collazzone area, Umbria, Central Italy
Natural Hazards and Earth System Sciences, 2006
We present the results of the application of a recently proposed model to determine landslide hazard. The model predicts where landslides will occur, how frequently they will occur, and how large they will be in a given area. For the Collazzone area, in the central Italian Apennines, we prepared a multi-temporal inventory map through the interpretation of multiple sets of aerial photographs taken between 1941 and 1997 and field surveys conducted in the period between 1998 and 2004. We then partitioned the 79 square kilometres study area into 894 slope units, and obtained the probability of spatial occurrence of landslides by discriminant analysis of thematic variables, including morphology, lithology, structure and land use. For each slope unit, we computed the expected landslide recurrence by dividing the total number of landslide events inventoried in the terrain unit by the time span of the investigated period. Assuming landslide recurrence was constant, and adopting a Poisson probability model, we determined the exceedance probability of having one or more landslides in each slope unit, for different periods. We obtained the probability of landslide size, a proxy for landslide magnitude, by analysing the frequency-area statistics of landslides, obtained from the multi-temporal inventory map. Lastly, assuming independence, we determined landslide hazard for each slope unit as the joint probability of landslide size, of landslide temporal occurrence, and of landslide spatial occurrence.
Natural Hazards and Earth System Sciences, 2002
We present a geomorphological method to evaluate landslide hazard and risk. The method is based on the recognition of existing and past landslides, on the scrutiny of the local geological and morphological setting, and on the study of site-specific and historical information on past landslide events. For each study area a multi-temporal landslide inventory map has been prepared through the interpretation of various sets of stereoscopic aerial photographs taken over the period 1941-1999, field mapping carried out in the years 2000 and 2001, and the critical review of site-specific investigations completed to solve local instability problems. The multi-temporal landslide map portrays the distribution of the existing and past landslides and their observed changes over a period of about 60 years. Changes in the distribution and pattern of landslides allow one to infer the possible evolution of slopes, the most probable type of failures, and their expected frequency of occurrence and intensity. This information is used to evaluate landslide hazard, and to estimate the associated risk. The methodology is not straightforward and requires experienced geomorphologists, trained in the recognition and analysis of slope processes. Levels of landslide hazard and risk are expressed using an index that conveys, in a simple and compact format, information on the landslide frequency, the landslide intensity, and the likely damage caused by the expected failure. The methodology was tested in 79 towns, villages, and individual dwellings in the Umbria Region of central Italy.
GIS analysis to assess landslide susceptibility in a fluvial basin of NW Sicily (Italy)
Geomorphology, 2008
Landslide hazard assessment, effected by means of geostatistical methods, is based on the analysis of the relationships between landslides and the spatial distributions of some instability factors. Frequently such analyses are based on landslide inventories in which each record represents the entire unstable area and is managed as a single instability landform. In this research, landslide susceptibility is evaluated through the study of a variety of instability landforms: landslides, scarps and areas uphill from crown. The instability factors selected were: bedrock lithology, steepness, topographic wetness index and stream power index. The instability landform densities computed for all the factors, which were arranged in Unique Condition Unit, allowed us to derive a total of three prediction images for each landslide typology. The role of the instability factors and the effects generated by the use of different landforms were analyzed by means of: a) bivariate analysis of the relationships between factors and landslide density; b) predictive power validations of the prediction images, based on a random partition strategy.The test area was the Iato River Basin (North-Western Sicily), whose slopes are moderately involved in flow and rotational slide landslides (219 and 28, respectively). The area is mainly made up of the following complexes: Numidian Flysch clays (19%, 1%), Terravecchia sandy clays (5%, 1%), Terravecchia clayey sands (3%, 0.3%) and San Cipirello marly clays (9%, 0%). The steepness parameter shows the highest landslide density in the [11–19°] class for both the typologies (8%, 1%), even if the density distributions for rotational slides are right-asymmetric and right-shifted. We obtained significant differences in shape when we used different instability landforms. Unlike scarps and areas uphill from crowns, landslide areas produce left-asymmetric and left-shifted density distributions for both the typologies. As far as the topographic wetness index is concerned, much more pronounced differences were detected among the instability landforms of rotational slides. In contrast, the flow landslides produce normal-like density distributions. The latter and the rotational slide landslide areas produce the highest density values in the class [5.5–6.7], despite an abrupt decreasing trend starting from the first class [3.2–4.4], which is generated by the density values of the rotational slide scarps and areas uphill from crowns. The stream power index at the foot of the slopes, which was automatically derived using a GIS-procedure, shows a positive correlation with the landslide densities marked by the maximum classes: [4.8–6.0] for flows, and [6.0–7.2] for rotational slides. The validation procedure results confirmed that the choice of instability landform influences the results of the susceptibility analysis. Furthermore, the validation procedure indicates that: a) the predictive models are generally satisfactory; b) scarps and zones uphill from crown areas are the most diagnostically unstable landforms, for flow and rotational slide landslides respectively.
Applied Sciences
The Italian territory is subject to a high level of hydrogeological instability that periodically results in the loss of lives, buildings and productive activities. Therefore, the recognition of areas susceptible to hydrogeological instability is the basis for preparing countermeasures. In this context, landslide susceptibility in the mid-Adriatic slope was analyzed using a statistical method, the weight of evidence (WoE), which uses information from several independent sources to provide sufficient evidence to predict possible system developments. Only flows, slides, debris flows and mud flows were considered, with a total of 14,927 landslides obtained from the IFFI (Inventory of Franous Phenomena in Italy) database. Seven climatic–environmental factors were used for mapping landslide susceptibility in the study area: slope, aspect, extreme precipitation, normalized difference vegetation index (NDVI), CORINE land cover (CLC), and topographic wetness index (TWI). The introduction of...
WIT Transactions on Ecology and the Environment, 2004
In the San Martino sulla Marrucina territory (Chieti province-central Italy) a large landslide phenomenon (>100 Mm 3) is present, causing the collapse of some residential buildings and road networks. The area is geologically very complex. The stratigraphy is characterised by clayey, sandy, conglomerate Upper Pliocene and Lower Pleistocene lithotypes. Quaternary deposits, consisting of alluvial or current terraced soils, grounds and cover detritus, are situated in discordance over the substratum. The hydrogeological system is complex and dislocated. The upper sandy-arenaceous bodies are not very large and do not ensure the persistence of a large water table. The superficial morphology, however, is such as to facilitate the permanency and the infiltration of the waters that saturate the soils within the terraces in counter-slope and the undrained areas, or rapidly seep into the fractures originating in the high zones of the slope. An analysis of the distribution of shapes and processes due to gravity enables us to formulate preliminary hypotheses about the movement in depth. In addition, the aim of this work is to carry out a susceptibility assessment of the zone and to verify the influence of the large landslide on the neighbourhood, utilising a numerical code to study the evolution of the phenomenon.
Geomorphology, 2012
This paper conducts a statistical analysis to determine shallow-landslide susceptibility in an approximately 7500-km 2 region of the south-eastern Alps (South Tyrol, Italy). The study applies the weight of evidence (WofE) method, which is useful in determining landslide susceptibility in large areas with complex geological and geomorphological settings. The statistical analysis and landslide susceptibility mapping are based on 882 past landslides, three geometric/topographic factors and two anthropogenic factors, which are the most relevant landslide predisposing factors. The quality of the proposed model, particularly the fitting performance, was assessed; the landslide database was divided into a training set to obtain the model and a validation set to estimate the model quality. The results show that the developed susceptibility model predicts an acceptable percentage (75%) of landslides. Therefore, the model can be useful and reliable for land planners and decision makers also due to its cost-effectiveness ratio.