Domenico Capolongo

Probabilistic modeling of uncertainties in earthquake-induced landslide hazard assessment

Probabilistic analysis is gaining more attention in the field of landslide hazard assessment, due to the possibility of taking into account estimation uncertainties and spatial variability of geological, geotechnical, geomorphological and seismological parameters. In this paper, an implementation of a simple approach to derive probabilistic earthquake triggered landslide hazard maps is described. The method is based on the simplified Newmark slope stability model, applied on a pixel-by-pixel basis, which fully integrates into current GIS computational environments. Uncertainties and fluctuations in input parameters are considered by treating these quantities as statistical distributions. Various probability density functions can be simulated through Monte Carlo techniques on a pixel-by-pixel basis, and the simulated samples are retained through all the computing steps. This allows the resulting quantities to be cast into probabilistic hazard maps, without restrictions about the symmetry or the mathematical complexity of the underlying distributions. First results on a test landslide site in Southern Italy show good performances for realistic landslide hazard zonation. The simplicity of the adopted framework allows the current approach to be easily expanded and improved the current approach.

SAR and InSAR for Flood Monitoring: Examples With COSMO-SkyMed Data

We apply high-resolution, X-band, stripmap COSMO-SkyMed data to the monitoring of flood events in the Basilicata region (Southern Italy), where multitemporal datasets are available with short spatial and temporal baselines, allowing interferometric (InSAR) processing. We show how the use of the interferometric coherence information can help to detect more precisely the areas affected by the flood, reducing false alarms and missed identifications which affect algorithms based on SAR intensity alone. The effectiveness of using the additional InSAR information layer is illustrated by RGB composites of various combinations of intensity and coherence data. Analysis of multitemporal SAR intensity and coherence trends reveals complex behavior of various field types, which we interpret through a Bayesian inference approach, based on a manual identification of representative scattering and coherence signatures of selected homogeneous fields. The approach allows to integrate external, ancillary information to derive a posteriori probabilistic maps of flood inundation accounting for different scattering responses to the presence of water. First results of this semiautomated methodology, using simple assumptions for the SAR signatures and a priori information based on the distance from river courses, show encouraging results, and open a path to improvement through use of more complex hydrologic and topo-hydrographic information.

A Bayesian Network for Flood Detection Combining SAR Imagery and Ancillary Data

Accurate flood mapping is important for both planning activities during emergencies and as a support for the successive assessment of damaged areas. A valuable information source for such a procedure can be remote sensing synthetic aperture radar (SAR) imagery. However, flood scenarios are typical examples of complex situations in which different factors have to be considered to provide accurate and robust interpretation of the situation on the ground. For this reason, a data fusion approach of remote sensing data with ancillary information can be particularly useful. In this paper, a Bayesian network is proposed to integrate remotely sensed data, such as multitemporal SAR intensity images and interferometric-SAR coherence data, with geomorphic and other ground information. The methodology is tested on a case study regarding a flood that occurred in the Basilicata region (Italy) on December 2013, monitored using a time series of COSMO-SkyMed data. It is shown that the synergetic use of different information layers can help to detect more precisely the areas affected by the flood, reducing false alarms and missed identifications which may affect algorithms based on data from a single source. The produced flood maps are compared to data obtained independently from the analysis of optical images; the comparison indicates that the proposed methodology is able to reliably follow the temporal evolution of the phenomenon, assigning high probability to areas most likely to be flooded, in spite of their heterogeneous temporal SAR/InSAR signatures, reaching accuracies of up to 89%.

Evaluating Earthquake-Triggered Landslide Hazard at the Basin Scale Through Gis in the Upper Sele River Valley

To evaluate techniques for assessing earthquake-triggeredlandslide hazard in the Southern Apennines (Italy), a GIS-based analysis was used to modelseismically induced slope deformations. Geological, geotechnical, geomorphological and seismologicaldata were integrated into a standard earthquake slope stability model. The model assessed thelandslide potential that existed during the 1980 Irpinian earthquake in the Upper Sele river Valley.The standard Newmark displacement analysis, widely used for predicting the location of shallowunstable slopes, does not take into account errors and/or uncertainties in the input parameters.Therefore, a probabilistic Newmark displacement analysis technique has been used. Probabilistictechniques allow, e.g., an estimation of the probability that a slope will exceed a certain criticalvalue of Newmark displacement. In our probabilistic method, a Monte-Carlo based simulation modelis used in conjunction with a GIS. The random variability of geotechnical data is modelled by probabilitydensity functions (pdfs), while for the seismic input three different regression laws wereconsidered. Input probability distributions are sampled and the resulting values input into empiricalrelations for estimating Newmark displacement. The outcome is a map in which to each siteis related a spatial probability distribution for the expected displacement in response to seismic loading.Results of the experiments show a high grade of uncertainty in the application of the Newmarkanalysis both for the deterministic and probabilistic approach in a complex geological setting suchas the high Sele valley, quite common in the Southern Apennines. They show a strong dependence onthe reliability of the spatial data used in input, so that, when the model is used at basin scale,results are strongly influenced by local environmental condition (e.g., topography, lithology, groundwatercondition) and decrease the model performance.

Factors Controlling Seismic Susceptibility of the Sele Valley Slopes: The Case of the 1980 Irpinia Earthquake Re-Examined

Most of the documented slope failures triggered by the 1980 Irpinia earthquake (Ms 6.9) occurred in the upper Sele valley epicentral area (southern Italy). The early investigations revealed some puzzling characteristics of the slope failure distribution, i.e., (i) the higher landslide concentration on the valley slopes located farther away from the earthquake fault; (ii) the predominance of re-activations over first-time movements. The analyses of factors controlling the landslide concentrations indicates that the differences in hydrological setting and in slope were the two main causal factors whereas the seismic shaking, according to the radiation pattern modelling, could have been characterised by a relatively low rate of decrease across the valley. The aspect of the slopes did not play a significant role. The differences in groundwater conditions between the western and eastern valley sides were probably enhanced by the earthquake. In addition to the probable pore-water pressure rise, the seismic shaking caused large increases in the flow of springs draining the western aquifer, and this made the adjacent flysch slopes more prone to landsliding. Data from the available literature suggest that the effects of earthquake-induced groundwater release on seismic landslide distribution is especially important for normal-fault events. The Sele valley case also indicates that the slope of the pre-existing landslides is an important factor controlling their susceptibility to seismic re-activations.

SIGNUM: A Matlab, TIN-based landscape evolution model

Several numerical landscape evolution models (LEMs) have been developed to date, and many are available as open source codes. Most are written in efficient programming languages such as Fortran or C, but often require additional code efforts to plug in to more user-friendly data analysis and/or visualization tools to ease interpretation and scientific insight. In this paper, we present an effort to port a common core of accepted physical principles governing landscape evolution directly into a high-level language and data analysis environment such as Matlab. SIGNUM (acronym for Simple Integrated Geomorphological Numerical Model) is an independent and self-contained Matlab, TIN-based landscape evolution model, built to simulate topography development at various space and time scales. SIGNUM is presently capable of simulating hillslope processes such as linear and nonlinear diffusion, fluvial incision into bedrock, spatially varying surface uplift which can be used to simulate changes in base level, thrust and faulting, as well as effects of climate changes. Although based on accepted and well-known processes and algorithms in its present version, it is built with a modular structure, which allows to easily modify and upgrade the simulated physical processes to suite virtually any user needs. The code is conceived as an open-source project, and is thus an ideal tool for both research and didactic purposes, thanks to the high-level nature of the Matlab environment and its popularity among the scientific community. In this paper the simulation code is presented together with some simple examples of surface evolution, and guidelines for development of new modules and algorithms are proposed.

Geomorphological map of the area between Craco and Pisticci (Basilicata, Italy)

This paper presents the results of geomorphological investigations carried out in Basilicata region (southern Italy) from the most external thrust front of the Apennines, where the town of Craco is located, to the adjacent sector of the Apennines foredeep (Fossa Bradanica; Pisticci area). The importance of the chosen area mostly resided in the presence of really diffuse running-waters and gravity-induced landforms which strictly affect urban areas. The geomorphological processes are linked with the Quaternary tectonic uplift affecting the Apennine front-Bradanic foredeep sectors. Series of field surveys, supported by aerial photo-interpretation, have led to the production of a geomorphological map at 1:16,000 scale which outlines the main processes and related landforms recognized in the study area. The latter are the result of the complex interplay of structural, gravitational and fluvial processes. Particular attention was devoted to the recognition, identification and mapping of landslides which affect the slope of the main villages (Craco and Pisticci), locally giving rise to hazardous conditions.

Landslide Triggering and Local Rainfall Thresholds in Bradanic Foredeep, Basilicata Region (Southern Italy)

It is recognised that a lot of the landslides occurred in the Mediterranean region are triggered by short intense storms. Due to its geological, geomorphological and climatic settings, the Bradanic Foredeep (Basilicata region) is affected by the widespread presence of landslides. The main objective of this paper is to identify the empirical triggering thresholds in Bradanic Foredeep and to investigate the role of antecedent rainfall. Using a variety of information sources, we have compiled a catalogue listing 97 rainfall events linked to landslides triggering in the investigated area. For each event in the catalogue, the exact or approximate location of the landslide and the time or period of initiation of the slope failure is known, together with information on the rainfall duration D, and the rainfall mean intensity I , that have resulted in the slope failure. The local rainfall threshold for the study area has been established using the statistical Frequentist approach. The comparison with regional thresholds proposed for other Italian regions has revealed that the Bradanic Foredeep thresholds are lower; which is probably due to the different quality of rainfall dataset. In fact, all the previous threshold have been evaluated starting from hourly data, while for the Basilicata region only daily data are available. Throughout this study we could not identify a significant correlation between antecedent rainfall and critical rainfall.

Climatic characteristics of middle-southern Apulia (southern Italy)

Abstract Please click here to download the map associated with this article. The purpose of this work is to make a climatic map in order to show several variables concerning climate type in a Mediterranean region. The study is focused on the middle and southern part of Apulia region, southern Italy, an area of approximately 12,170 km2 between 39°45′ and 41°30′ N and 15°40′ and 18°40′ E. The map uses mean annual temperature as a background for the number of dry and cold months, and is supplemented with secondary maps which highlight the characteristics of a dry climate. Rainfall and temperature records of 46 thermo-pluviometric stations, over a 30 year period, were interpolated by kriging: the main map takes into account the Rapetti and Vittorini pattern, while for the other graphics the Thornthwaite and Mather water balance model was followed. Both these methods focus on factors which determine drought in a land of low rainfall such as Apulia region.

Multi-method Evaluation of Denudation Rates in Small Mediterranean Catchments

The paper presents the results of the research tasks of the Quantitative Geomorphology Working Group (of the Italian Association of Physical Geography and Geomorphology) focused on multi-method evaluation of denudation rates in small catchments of Italy. Several study areas are compared with the goal of quantifying the morphodynamic evolution in different response times and with traditional and innovative techniques. The final aims are the direct erosion monitoring, the geomorphic analysis for the comprehension of drainage basin morphodynamics, up to the geomorphological hazard evaluation. The catchments are key Mediterranean areas particularly sensitive to climatic and anthropic modifications. The efforts of the Working Group are finalized to favour scientific collaboration activities among members with the aim of strengthen the potential of Quantitative Gomorphology in morphodynamic studies.