Claudio Puglisi

GIS Methodology to Assess Landslide Susceptibility: Application to a River Catchment of Central Italy

Abstract Please click here to download the map associated with this article. This paper illustrates a geographic information system (GIS) supported methodology for the assessment of landslide susceptibility. The methodology involves four operational steps: survey, site analysis, macroarea analysis and susceptibility analysis. The Survey includes the production (or acquisition) of a large-scale litho-technical map, a large-scale geomorphological map, a detailed inventory of past and present landslide events, and a high resolution DTM (Digital Terrain Model. Site analysis leads to the definition of discriminating parameters (commonly, lithological and morphometric conditions necessary but not sufficient to trigger a landslide of a given type) and predisposing factors (conditions that worsen slope stability but are not sufficient to trigger a landslide of a given type in the absence of discriminating parameters). The different predisposing factors are subdivided into classes, whose intervals are established by descriptive, statistical analysis of landslide inventory data. A numerical index, based on the frequency of landslide occurrence, quantifies the contribution of each class to slope instability. Macro-area analysis includes the generation of Litho-Morphometric Units (LMU) by overlaying discriminating parameters, manual drawing of LMU envelopes (macro-areas), generation of predisposing factor maps from the spatial distribution of predisposing factors, and heuristic weighting of predisposing factor indices. Susceptibility analysis includes the generation of Homogeneous Territorial Units (HTU) by overlaying macroareas and predisposing factor maps, and the application of a susceptibility function to the different HTU. The resulting values are normalized before the generation of the landslide susceptibility maps. The methodology has been applied to the Fiumicino River catchment, located in the western side of Latium Apennine (Central Italy) between 200 and 1300 m a.s.l. and developed on Late Miocene calcarenites, sandstones with clay intercalations, and marls. The resulting landslide susceptibility maps will be employed in environmental management. They also represent the preliminary step for the assessment of landslide hazard and risk.

Preliminary Remarks on Monitoring, Geomorphological Evolution and Slope Stability of Inca Citadel of Machu Picchu (C101-1)

The geology of Machu Picchu area is characterized by granitoid bodies that had been emplaced in the axial zones of the main rift system. Deformation of the granite, caused by cooling and tectonic phases, originated 4 main joint sets, regularly spaced (few decimeters to meters). Several slope instability phenomena have been identified and classified according to mechanism, material involved and state of activity. They are mainly related to rock falls, debris flows, rock slides and debris slides. Origin of phenomena is kinematically controlled by the structural setting and relationship with slope face (rock falls, rock slide and debris slides); the accumulated materials are the source for debris flows. Geomorphological evidences of deeper deformations are currently under investigation.

The RUSLE erosion index as a proxy indicator for debris flow susceptibility

Debris flows represent dangerous occurrences in many parts of the world. Several disasters are documented due to this type of fast-moving landslides; therefore, natural-hazard assessment of debris flows is crucial for safety of life and property. To this aim, much current work is being directed toward developing geotechnical-hydraulic models for the evaluation of debris flow susceptibility. A common base for such current models is parameterization of background predisposing and triggering factors such as inherent characteristics of geo-materials, topography, landscape and vegetation cover, rainfall regime, human activities, etc. which influence the occurrence of these processes on slopes. The same factors are also taken into account in soil erosion prediction models. Consequently, it seems worth investigating the effectiveness of the soil erosion index as debris flows susceptibility indicator. To this aim, a logistic regression analysis was carried out between the erosion index assessed by means of the Revised Universal Soil Loss Equation (RUSLE) model and the inventory of debris flows that have occurred in an area in Sicily (Southern Italy). Model assumptions were verified and validated by means of a series of statistical tools. Different possible scenarios were also evaluated by considering hypothetical changes in soil erosion rate under different rain erosivity conditions. Notwithstanding the rough approximations in model data collection, the outcomes appear encouraging.

Monitoring, Geomorphological Evolution and Slope Stability of Inca Citadel of Machu Picchu: Results from Italian INTERFRASI project

The Geology of Machu Picchu area is characterised by granitoid bodies that had been emplaced in the axial zones of the main rift system. Deformation of the granite, caused by cooling and tectonic phases, originated 4 main joint sets, regularly spaced (few decimetres to metres). Several slope instability phenomena have been identified and classified according to mechanism, material involved and state of activity. They are mainly related to rock falls, debris flows, rock slides and debris slides. Origin of phenomena is kinematically controlled by the structural setting and relationship with slope face (rock falls, rock slide and debris slides); the accumulated materials is the source for debris flow. Geomorphological evidences of deeper deformations are currently under investigation.

Geomorphology Hazard Assessment of Giampilieri and Briga River Basins After the Rainfall Event on the October 1, 2009 (Sicily, Italy)

Mud and debris flows constitute a serious threat for several Italian regions as attested by recent several disasters attributable to such phenomena. The adoption of effective mitigation measures is complicated by the difficulty in predicting spatial and intensity features of future events.

Multi-Temporal and Quantitative Geomorphological Analysis on the Large Landslide of Craco Village (M118)

The village of Craco (Basilicata, Italy), is being affected by severe landslide phenomena mainly due to the geological and geomorphological setting of the area. The village has been interested by a progressive abandon of the population after the occurrence in the time of landslides and earthquakes that caused the disruption of large portions of the urban settlement. Several landslide typologies can be recognized in the area: rock-falls in the upper part of the hill, rotational and translational earth slides, earth-flows, rock lateral spreading. The main purpose of the paper is to reconstruct the evolution of the geological and morphological dynamics acting on the southern slope of Craco, where the largest landslides occurred in the past.

Heuristic Method for Landslide Susceptibility Assessment in the Messina Municipality

October 1st 2009 a heavy rainfall caused more than one thousand debris flows in two small basins south of Messina town (North–East Sicily, Italy). After the disaster Messina Municipality entrusted the risk assessment of its whole territory to a geomorphology and GIS team, led by ENEA, that applied and improved a heuristic method aimed at the identification of the areas prone to landslide triggering, based on the recognition of physical and dynamical characteristics of phenomena. This landslide susceptibility method is a GIS based process that consists in four steps: Field Survey, Site Analysis, Macro-Area Analysis and Susceptibility Analysis. Through the Field Survey of natural and anthropic conditions of past and recent phenomena a landslide inventory is generated, and each thematic map is stored in a GIS database. In the Site Analysis a univariate statistical analysis of the inventory leads to classify each causative factor as a discriminating parameter (condition necessary for slope instability) or as a predisposing factor (condition that works together in worsening slope stability). In the Macro-Area Analysis the GIS overlay of all thematic maps is performed to recognize, in surrounding areas, features similar to those of past events. Finally a susceptibility function runs the weighted sum of Predisposing Factors in zones where all Discriminating Parameters are present, deriving the Susceptibility Map. The here discussed heuristic GIS method allows the integration of multidisciplinary knowledge, both quantitative and qualitative, thus exploiting field experience.

Debris Flow Risk Assessment in the Aguas Calientes Village (Cusco, Perù)

In this paper a landslide risk assessment in the area of Aguas Calientes village (Machu Picchu, Cusco, Peru) is applied. A study carried out into a capacity building project (FORGEO) was focused on localising source areas and runout of debris flows triggered by heavy rainfall in the Alcamayo catchment and on assessing debris flow intensity. Starting from an inventory of several previous debris flows occurred in the area, an evaluation of the local predisposing parameters to these events was used as input for susceptibility and hazard GIS based analysis. Empirical formulas reported in the literature were adapted to the research area context to estimate the runout of potential events. An analysis of exposure of structures and infrastructures was also performed during the project and high residual risk conditions were found for the Aguas Calientes village. These results may aid local authorities involved in land use planning, management policies and landslide risk reduction.

Landslide Hazard Assessment Project in the Messina Municipality Area (Sicily, Italy)

In the last 4 years Messina Municipality has been hit by rainfall events that triggered a great number of debris flows. Due to 2009 event ENEA started landslide hazard researches in the south of the Municipality. Messina territory (210km2) is located at the NE culmination of Peloritani Range, formed by seven metamorphic Units covered by late orogenic terrigenous formations and by Plio-Pleistocene deposits. Steep slopes lead to high erosion rates, that increased in last years because of intense rainfall. The first step of the hazard assessment method is an inventory of landslides, followed by the detection of landslide parameters. Through GIS analysis of this parameters landslide susceptibility is assessed. Geomorphological analysis allows evaluating the runout and energy of the future events. Rainfalls data analysis allows definition of triggering threshold for the area. These parameters will be tested in a test site field for the measurement of soil saturation.

Rockfalls Monitoring Along Eastern Coastal Cliffs of the Favignana Island (Egadi, Sicily): Preliminary Remarks

Favignana island (Sicily, Italy) is a historical and environmental attraction site frequented by tourists during the long warm season of the year. For several centuries the calcareous sandstone outcropping in the east side of the island has been extracted and used as building stone. Actually the quarries and the caves are undergoing to erosional and gravitational processes that are influencing the touristic use. As well as putting at risk the safety of people attending the area, the diffused rock falls are likely to jeopardize sites of great anthropological value that, once destroyed, can no longer be reconstructed. An integrated monitoring project of the cliffs is aimed to identify the most active areas and to provide support to the local government’s policies in the implementation of mitigation measures. If adequate measures will be taken in the future, operators and users of the tourist circuit will have the opportunity to enjoy these amazing areas with lower level of landslide risk.