Giulio Iovine

Computer simulation of natural phenomena for hazard assessment

Hazard assessment of dangerous natural phenomena is increasingly important as the toll in loss of human life and property in the media attests. The frequent and varied use of simulation methodologies is changing the attitudes of scientists in their approach to solving hazard problems. This process is leading towards the future possibility of managing complex natural, artificial, and mixed systems, the complexity of which excludes analytical solutions, or even worse, the use of differential equations. Powerful computers now allow approximate numerical methods based on space/time discretisation to be developed for quantitative modelling and simulation of complex phenomena. Furthermore, other challenges may arise due to the nature of the phenomena: some parameters of the model cannot be independently determined, either for fundamental reasons (e.g. they may be empirical, not physical) or for practical reasons (e.g. direct measures are not allowed); their values could possibly be found by comparing the model outcome with a set of experimental data. The papers collected in this issue are a selection of the original 35 studies presented at session NH23 of the EGS-AGU-EUG Joint Assembly (Nice, April 2003). They represent, in the opinion of the guesteditors, an interesting window on the difficult problem of analysing complex natural phenomena through modelling techniques, and on evaluating the associated hazards. For example, the research of Yuk, Yim & Liu (submarine mass-movement generated waves) and that of Patra, Nichita, Bauer, Pitman, Bursik & Sheridan (debris flows) use methodologies for finding approximate solutions to complex systems of differential equations, to describe the natural phenomena under study. Simulations validate these models on real cases or

Parallel genetic algorithms for optimising cellular automata models of natural complex phenomena : An application to debris flows

Abstract Cellular automata models of natural complex phenomena may depend on a set of parameters which can significantly influence the global dynamics of the simulated events. In order to reliably apply such models for predictive purposes, their parameters have to be estimated with the greatest possible accuracy. However, no standardised optimisation techniques exist in this specific research field. Genetic Algorithms (GAs) offer a possible solution: they are parallel algorithms, and can be easily implemented to exploit the simultaneous use of multiple CPUs, thereby greatly reducing the execution time. An application of a parallel GA to the optimisation of a cellular automata model for the simulation of debris flows characterised by strong inertial effects is presented. The May 1998, Curti-Sarno (Italy) debris flow has been selected as a case study for the optimisation of the model. Theoretical considerations on the dynamics of the adopted GA are discussed, with reference to two different fitness functions applied to an idealised case study. Results demonstrated the usefulness of the approach, in terms of both computing time and quality of performed simulations. Moreover, experiments on the idealised case study pointed out that the simplest fitness function (only based on the comparison of affected areas) could conveniently be adopted for calibration purposes.

First simulations of the Sarno debris flows through Cellular Automata modelling

Abstract Cellular Automata (CA) can be efficiently applied in the simulation of complex natural processes. They represent an alternative approach to classical methods based on the resolution of differential equations. In this paper, the general frame and the latest developments of the Cellular Automata model SCIDDICA (Simulation through Computational Innovative methods for the Detection of Debris flow path using Interactive Cellular Automata) for simulating debris-flow phenomena are presented. Landslides characterised by a dominant flow-type (e.g. earth flows, debris flows, debris avalanches) can be considered as dynamical systems, subdivided into elementary parts that evolve, exclusively, as a consequence of local interactions. In SCIDDICA, space and time are discrete: in particular, the space in which the phenomenon evolves is represented by square cells, whose states describe the considered physical characteristics; time is implicit in the steps of model computation. The peculiarities of the structure permitted to extend SCIDDICA first release, in order to progressively account for more complex phenomenological aspects of the considered landslides. In this paper, examples of application of SCIDDICA to three real landslide events are presented. After briefly describing earlier simulations of the 1992 Tessina (Italy) earth flow and of the 1984 Mt. Ontake (Japan) debris avalanche, first attempts at modelling a debris flow that occurred in 1998 at Sarno (Italy) are discussed. The model has been validated through the reconstruction of the initial topographic and geomorphological conditions of a selected, typical phenomenon (which occurred at Chiappe di Sarno–Curti, on May 1998), and by successively comparing the simulation results with the actually observed debris-flow path. Even though improvements to the algorithms are still needed, and further testing of parameters on a more representative sample of phenomena desirable, first simulations of the Curti landslide have demonstrated the reliability of SCIDDICA in the assessment of debris-flow susceptibility.

Landslide inventory map for the Briga and the Giampilieri catchments, NE Sicily, Italy

On 1 October 2009, a high intensity storm hit the Ionian coast of Sicily, SW of Messina, Italy. The Santo Stefano di Briga rain gauge, located 2 km W of the Ionian coast, recorded 225 mm of rain in seven hours. The intense rainfall event triggered abundant slope failures, and resulted in widespread erosion and deposition of debris along ephemeral drainage channels, extensive inundation, and local modifications of the coastline. Landslides occurred in a territory prone to slope failures, due to the local geological and geomorphological settings. Many landslides were related to the presence of roads lacking adequate drainage. Abandoned terraced slopes lacking proper drainage, and unmaintained dry walls were also related to slope failures. Damage was particularly severe in small villages and at several sites along the transportation network. The shallow landslides and the inundation resulted in 37 fatalities, including 31 deaths and six missing persons, and innumerable injured people. After the event, an accurate landslide inventory map was prepared for the Briga and the Giampilieri catchments. The map shows: (i) the distribution of the event landslides triggered by the 1 October 2009 rainfall event; (ii) the distribution of the pre-existing slope failures; and (iii) other geomorphological features related to fluvial processes and slope movements. The landslide inventory map was prepared at 1:10,000 scale through a combination of field surveys and photo-interpretation of pre-event and post-event, stereoscopic and pseudo-stereoscopic, aerial photography. Different types of aerial photographs were analysed visually to prepare the landslide inventory map. The event landslides were mapped through the interpretation of pseudo-stereoscopic colour photographs taken shortly after the event at 1:3500 scale, combined with digital stereoscopic photographs at approximately 1:4500 scale, taken in November 2009. The pre-event landslides and the associated geomorphological features were mapped using 1:33,000 scale aerial photographs flown in 1954, 1955, and 2005. The event and pre-existing landslides were checked in the field in the period October–November 2009.

Origin and distribution of different types of sinkholes in the plain areas of Southern Italy

Sinkholes constitute a significant risk in many karst areas, and may even threat human safety. Collapse sinkholes that occur catastrophically without showing premonitory signs may result in severe economic losses and casualties. In the last years, research on sinkholes and related detrimental effects has significantly increased in Italy, in the aftermath of remarkable events. Aimed at analysing the peculiar conditions which lead to sinkhole occurrence in Southern Italy, a set of cases in the plain areas of Campania, Apulia and Calabria is discussed. The considered regions show a wide variety of environmental conditions. In Campania, the plains are underlain by alluvial deposits with intercalations of volcaniclastic sediments. Sinkholes are generally located along the Tyrrhenian margin of the carbonate massifs or within intramontane Apennine basins. In Apulia, a flat and elongated peninsula, most of the cases occur on calcarenites overlying limestone bedrock along the coast. In Calabria, one of the most seismogenic Italian regions, the surveyed cases seem to be attributable mainly to earthquake-induced liquefaction. The article provides a first glance on the variety of sinkholes in the plain areas of Southern Italy, to highlight the possibility of further subsidence events in the considered regions, as well as in other comparable areas of the country.

Catalogue of Rainfall Events with Shallow Landslides and New Rainfall Thresholds in Italy

In Italy, rainfall-induced shallow landslides are frequent and harmful phenomena. The prediction of their occurrence is of social significance for civil protection purposes. For the operational prediction of rainfall-induced shallow landslides empirical rainfall thresholds based on the statistical analysis of past rainfall conditions that triggered slope failures are commonly used. The paper describes a catalogue of 1981 rainfall events, which caused 2408 shallow landslides in Italy in the period 1996–2012. Information on rainfall-induced landslides was collected searching chiefly online newspaper archives, blogs, and fire brigade reports. For each documented failure, we reconstructed the triggering rainfall conditions (rainfall duration D and cumulated rainfall E) using national and regional rain gauge networks. We analysed the rainfall conditions to determine new ED rainfall thresholds for Italy. The calculated thresholds can be implemented in a landslide forecasting system to mitigate landslide hazard and risk.

Simulating the Curti–Sarno debris flow through cellular automata: the model SCIDDICA (release S2)

Cellular automata (CA) are based on a regular division of the space in cells. Each cell embeds an identical finite automaton, whose input is given by the states of neighbouring cells. The transition function r of the CA is made of a set of rules, simultaneously applied, step by step, to each cell of the cellular space. Rules are derived by subdividing, in computational terms, the physical phenomenon into a set of independent, elementary processes. By properly combining each elementary result, the behaviour of the phenomenon can be simulated. Debris flows are dense mixtures of sediment and water, which surge down the slopes and along the drainage system, characterised by severe destructive potential. They can be described in terms of local interactions among their elementary portions, and can thus be efficiently modelled through CA. Debris-flows rheologic equations cannot be easily solved without making substantial simplifications. By applying CA, a phenomenological description––able to overcome resource computational limits––can be obtained. On May 1998, hundreds of soil slip-debris flows were triggered by exceptional rains in Campania (Italy), mostly on the slopes of Pizzo dAlvano. Aiming at modelling purposes, the Curti debris flow was selected as a case study, among the whole population of landslides triggered by the event. The general frame of SCIDDICAS2 is inherited from previous releases, recently applied for the simulation of the 1992 Tessina (Italy) earth flow and of the 1984 Mt. Ontake (Japan) debris avalanche. Since its S1 release, the model satisfactorily simulated the Curti–Sarno debris flow. Latest improvements to the transition function led to the S2 release, and to better simulations (presented here). SCIDDICA exhibits a notable flexibility in modelling and simulating flow-like landslides. It could be usefully applied in hazard mapping (also through a statistical approach), and in evaluating the effects of either human works or ‘‘accidents’’ along the path of the flow. � 2002 Elsevier Science Ltd. All rights reserved.

Preface: Modelling, computer-assisted simulations, and mapping of dangerous phenomena for hazard assessment

The topic of this special issue certainly deserves much more than the following few comments of introduction. Our remarks here are aimed at better defining the scientific framework within which research activities on this topic e and hence the papers here collected e have generally been conducted up to date. Evaluating the hazards posed by geological phenomena constitutes, within the broader framework of ‘‘prediction’’, one of the most significant challenges of modern scientific research. As a matter of fact, there has always been a strong demand from Government Authorities for suitable and powerful tools for analysing and predicting hazardous situations for civil protection purposes. With the aim of evaluating the variety of available techniques for hazard assessment, they could perhaps be classified solely on the basis of the type of phenomenon that they describe (e.g. earthquakes, floods, hurricanes, landslides, volcanic eruptions, tsunamis, forest fires, and water/air pollution). Nevertheless, similarities in methodologies and general trends of conceptual evolution immediately demonstrate that many approaches of analysis have broader applications, which go well beyond peculiarities related to the specific type of phenomenon for which they were originally implemented. In the last decades, increasingly powerful computing environments and software codes, combined with refined techniques of measure, have progressively become available. We are now still ‘‘in the middle of the ford’’, well within such an evolutionary phase, which appears somewhat confused and must also deal with the wider topic of ‘‘complexity’’. The stakes involve the passage from a purely descriptive kind of science, to a mainly predictive one e which is exactly what the public expects from the scientific community. In this context, the word ‘‘complexity’’ does not refer to algorithmic complexity, but rather to the notion of complex systems (i.e. aggregates made of different, generally non-linearly interacting parts, whose global evolution cannot be returned to the sum of the elementary behaviours of their constituent parts). The system is complex with reference to an observer, who is able to distinguish the local from the global scale, and to measure the elementary interactions. Multiple levels of description can be selected for a given system, either in typological, temporalor spatial-scale terms, which are strictly related to the adopted observationaleexperimental choices (expressing the

Introduction to the special issue “Landslides: forecasting, hazard evaluation, and risk mitigation”

The papers collected in this special issue of Natural Hazards were originally presented as oral or poster contributions in the sessions ‘‘Innovative approaches for evaluation of the landslide hazard and mitigation of the landslide risk’’ and ‘‘Landslide forecasting’’, which were part of the scientific program of the Geoitalia 2009 meeting, the 7th Italian Forum of the Earth Sciences, held in Rimini, Italy, from 9 to 11 September 2009. The eighteen papers comprising the special issue of Natural Hazards discuss topics related to techniques, tools, and methods for landslide identification, forecasting, hazard evaluation, and the mitigation of landslide risk. The issue opens with the two keynote lectures invited in the sessions: in the first keynote, Jaboyedoff and co-workers review the application of light detection and ranging (LIDAR) technology for landslide investigation, including the study of slides, rockfalls, and debris flows. The authors discuss critically the application of LIDAR very-high-resolution terrain elevation data for the detection and characterization of landslides, for hazard assessment and susceptibility modeling, and for landslide monitoring and modeling. In the second keynote, Günther and co-workers, discuss a GIS-based deterministic approach for the spatial evaluation of the geometrical and kinematical properties of rock slopes. Based on spatially distributed directional information on planar geological fabrics, and DEM-derived topographic attributes, the internal geometry of the rock slopes is characterized. The obtained information, in combination with hydraulic and strength data on the geological discontinuities, can be used to prepare scenario-based rock-slope stability evaluations, at different geographical scales.

Gravity-Accommodated ‘Structural Wedges’ Along Thrust Ramps: A Kinematic Scheme of Gravitational Evolution

In active geodynamic areas, such as the Italian Southern Apennines, the specific structural conditions have a profound effect on both the superficial and deep gravitational evolution of slopes. Chain sectors commonly exhibit structural complexities due to the superimposition, in space and time, of diverse tectonic stress fields. In this paper, attention is focused on particular structural configurations, connected to the tectonic quaternary phases that have affected the Southern Apennines, constituting a peculiar type of lateral spread gravitational deformations – which have not been previously described.The study area is characterized by regional roughly east-verging overthrusts (Holigo–Miocene). Superimposed on these, is a system of transpressive thrust ramps (Quaternary), connected to the activity of strike-slip faults. The latest tectonic phase, still active, has been characterized by an extensional stress field, which has produced differentiated uplifts along normal faults. All these factors have encouraged an intense and widespread processes of erosion, the creation of considerable relief energy and the development of both superficial and deep gravitational phenomena.It has been ascertained that the late extensional phases favoured gravitational reactivations (with normal movements) along those most recent thrust ramps whose attitude was kinematically consistent with the main extension direction of the stress field. Such reactivations were ‘accommodated’ by antithetic neo-formational structures – these are also characterized by normal kinematics. Overall, such mechanisms lead to the individuation of wedge-shaped rock portions delimited by the normally reactivated thrust ramps, on one side, and by the antithetic structures, on the other.Structural wedges represent a particular type of lateral spread phenomena. On the basis of their orientation with respect to the orography, three typical situations have been defined: (1) wedge perpendicular to the ridge; (2) wedge parallel to the ridge; (3) wedge oblique to the ridge.In this paper three Calabrian case studies, exemplifying the above-mentioned situations, are described. The same framework can be applied to sectors of chain with an analogous structural setting, for a better understanding of the kinematic features of observed gravitational phenomena.