Test of Fuzzy Logic Rules for Landslide Susceptibility Assessment

16 p.International audienceLandslide Susceptibility Assessment (LSA) is defined as the spatial probability for a landslide to be generated in an area for many environmental factors. Currently, two approaches are used: (i) the qualitative approach based on expert opinion and knowledge of the relationship between the observed phenomenon and some predisposing factors and (ii) the statistical approach based on the statistical analysis of the relationship between the observed landslide and some predisposing factors. This paper proposes an exploratory attempt to use Fuzzy Logic Rules for mapping landslide susceptibility. The technique allows to describe the role of each predisposing factor (predictive variable) and their optimal combination. The best predictive variables identified by Fuzzy Logic are then introduced in a statistical bivariate model. The simulated maps obtained by both approaches are then compared and evaluated with an expert map, build with the prescribed rules of the French PPR (Plan de Prévention des Risques) methodology, and considered as a map of reference

Quasi-Newton inversion of seismic first arrivals using source finite bandwidth assumption: Application to subsurface characterization of landslides

International audienceCharacterizing the internal structure of landslides is of first importance to assess the hazard. Many geophysical techniques have been used in the recent years to image these structures, and among them is seismic tomography. The objective of this work is to present a high resolution seismic inversion algorithm of first arrival times that minimizes the use of subjective regularization operators. A Quasi-Newton P-wave tomography inversion algorithm has been developed. It is based on a finite frequency assumption for highly heterogeneous media which considers an objective inversion regularization (based on the wave propagation principle) and uses the entire source frequency spectrum to improve the tomography resolution. The Fresnel wavepaths calculated for different source frequencies are used to retropropagate the traveltime residuals, assuming that in highly heterogeneous media, the first arrivals are only affected by velocity anomalies present in the first Fresnel zone. The performance of the algorithm is first evaluated on a synthetic dataset, and further applied on a real dataset acquired at the Super-Sauze landslide which is characterized by a complex bedrock geometry, a layering of different materials and important changes in soil porosity (e.g. surface fissures). The seismic P-wave velocity and the wave attenuation are calculated, and the two tomographies are compared to previous studies on the site

Automated mapping of coastline from high resolution satellite images using supervised segmentation

International audienceIn this article, we are dealing with the problem of coastline extraction in High and Very High Resolution multispectral images. Locating precisely the coastline is a crucial task in the context of coastal resource management and planning. According to the type of coastal units (sandy beach, wetlands, dune, cliff), several definitions for the coastline has to be used. In this paper a new image segmentation method, which is not fully automated but relies on a low intervention of the expert to drive the segmentation process, is proposed. The method combines both a marker-based watershed transform (a standard image segmentation method) and a supervised pixel classification. The user inputs only consist of some spatial and spectral samples which are defined depending on the coastal environment to be monitored. The applicability of the method is tested on various types of coastal environments in France

Quasi-Newton algorithm using Fresnel wavepaths and frequency increase for P-wave tomography inversion: application to a landslide in the South French Alps

EGU2012-4323During last decases, geophysical methods have become of a great interest in geomorphological studies. Because they are well adapted to retrieve geological structures as variations in the spatial and temporal dimensions of rocks properties, they were widely developed for improving landslides understanding. Landslide studies generally involve the use of several geophysical methods, but among them, seismic surveys are well adapted to identify the slope's main structures. The wave propagation being mainly controlled by elastic properties of the medium, this method makes the interpretation easier since results are often well correlated with geotechnical observations. More generally, it provides information on the mechanical state of the soils with an acceptable spatial resolution. This structure is of first importance when studying clayey landslides as the Super-Sauze one. It occurred in the 1960s with the falls of large blocks and has developed continually covering an intact paleotopography. This succession of crests and gullies has been studied by geotechnical measurement and geophysics. It plays a large role in the behavior of the flow by delimiting preferential water and material pathways and compartments with different kinematics, mechanical and hydro dynamical characteristics. For the first time, a 3D geological model has been created from the fusion of multi-source data by Travelletti and Malet (2011), but it appears that geophysical methods can't capture the sharp geometry of the paleotopography. To improve such models and the numerical modeling resulting we propose a Quasi-Newton algorithm based on the Fresnel-wavepath and the frequency increase to the invert P-wave velocity fiel

Automatic malfunction diagnosis by on-line expert system for underground mobile machines

International audienceIn many Underground workings, either for mineral production or for creating lines of communicauon, mobile machines have to operate under conditions that are very difficult for personnel and equipment. Problems such as excessive dust, rock falls, high temperature and humidity, or the presence of an explosive atmosphere are not uncommon. Today, it is possible to monitor such machinery from a surface Station, in real time, using a highiy reliable digital transmission System (developed by INERIS), at distances of up to 10 km from the working. Similarly, difficulties arising from in-situ maintenance have led to the development of an on-line malfunction diagnosis System that can detect such malfunction and halt Operation by a conditionnal programmed stop. The Software has been developed using Expert System techniques with GENESIA l (EdF-STERIA) and the hardware is compatible with IBM PC-AT. On-line communication is under JBUS protocol. Full analysis (data acquisition - processing - Output) takes 20 seconds. The system can be intemipted at any moment to obtain correct Status of Operation

Time-variable 3D ground displacements from High-Resolution Synthetic Aperture Radar (SAR). Application to La Valette landslide (South French Alps).

International audienceWe apply an image correlation technique to multi-orbit and multi-temporal High-Resolution (HR) SAR data. Image correlation technique has the advantage of providing displacement maps in two directions; e.g. the Line of Sight direction (LoS) and the Azimuth direction. This information, derived from the two modes of data acquisition (ascending and descending), can be combined routinely to infer the three dimensional surface displacement field at different epochs. In this study, a methodology is developed to characterize the displacement pattern of the large La Valette landslide (South French Alps) using TerraSAR-X images acquired in 2010. The results allow mapping the dynamics of different units of the La Valette landslide at high spatial resolution. The study demonstrates the potential of this new application of High Resolution SAR image correlation technique for landslide ground surface deformation monitoring

Prediction of changes in landslide rates induced by rainfall

National audienceThis work focuses on the use of a combined statistical-mechanical approach to predict changes in landslide displacement rates from observed changes in rainfall amounts. The forecasting tool associates a statistical impulse response (IR) model to simulate the changes in landslide rates by computing a transfer function between the input signal (e.g. rainfall) and the output signal (e.g. displacements) and a simple 1D mechanical (MA) model (e.g. visco-plastic rheology) to take into account changes in pore water pressures. The models have been applied to forecast the displacement rates at the Super-Sauze landslide (South East France), one of the most active and instrumented clayey landslide in the European Alps. Results indicate that the three models are able to reproduce the displacement pattern in the general kinematic regime with very good accuracy (succession of acceleration and deceleration phases); at the contrary, extreme kinematic regimes such as fluidization of part of the landslide mass are not being reproduced: this statement, quantitatively characterised by the Root Mean Square Error between the model and the observations, constitutes however a robust approach to predict changes in displacement rates from rainfall or groundwater time series, several days before it happens. The variability of the results, depending in particular on the fluidization events and on the location of displacement data is discussed

Progress in Landslide Susceptibility Mapping over Europe Using Tier-Based Approaches

The European Thematic Strategy for Soil Protection aims, among other objectives, to ensure a sustainable use of soil. The legal instrument of the strategy, the proposed Framework Directive, suggests identifying priority areas of several soil threats including landslides using a coherent and compatible approach based on the use of common thematic data. In a first stage, this can be achieved through landslide susceptibility mapping using geographically nested, multi-step tiered approaches, where areas identified as of high susceptibility by a first, synoptic-scale Tier (Tier 1) can then be further assessed and mapped at larger scale by successive Tiers. In order to identify areas prone to landslides at European scale (Tier 1), a number of thematic terrain and environmental data sets already available for the whole of Europe can be used as input for a continental scale susceptibility model. However, since no coherent landslide inventory data is available at the moment over the whole continent, qualitative heuristic zonation approaches are proposed. For Tier 1 a preliminary, simplified model has been developed. It consists of an equally weighting combination of a reduced, continent-wide common dataset of landslide conditioning factors including soil parent material, slope angle and land cover, to derive a landslide susceptibility index using raster mapping units consisting of 1 x 1 km pixels. A preliminary European-wide susceptibility map has thus been produced at 1:1 Million scale, since this is compatible with that of the datasets used. The map has been validated by means of a ratio of effectiveness using samples from landslide inventories in Italy, Austria, Hungary and United Kingdom. Although not differentiated for specific geomorphological environments or specific landslide types, the experimental model reveals a relatively good performance in many European regions at a 1:1 Million scale. An additional Tier 1 susceptibility map at the same scale and using the same or equivalent thematic data as for the one above has been generated for six French departments using a heuristic, weighting-based multi-criteria evaluation model applied also to raster-cell mapping units. In this experiment, thematic data class weights have been differentiated for two stratification areas, namely mountains and plains, and four main landslide types. Separate susceptibility maps for each landslide type and a combined map for all types have been produced. Results have been validated using BRGM's BDMvT landslide inventory. Unlike Tier 1, Tier 2 assessment requires landslide inventory data and additional thematic data on conditioning factors which may not be available for all European countries. For the Tier 2, a nation-wide quantitative landslide susceptibility assessment has been performed for Italy by applying a statistical model. In this assessment, multivariate analysis was applied using bedrock, soil and climate data together with a number of derivatives from SRTM90 DEM. In addition, separate datasets from a historical landslide inventory were used for model training and validation respectively. The mapping units selected were based on administrative boundaries (municipalities). The performance of this nation-wide, quantitative susceptibility assessment has been evaluated using multi-temporal landslide inventory data. Finally, model limitations for Tier 1 are discussed, and recommendations for enhanced Tier 1 and Tier 2 models including additional thematic data for conditioning factors are drawn. This project is part of the collaborative research carried out within the European Landslide Expert Group coordinated by JRC in support to the EU Soil Thematic Strategy. It is also supported by the International Programme on Landslides of the International Consortium on Landslides.JRC.DDG.H.7-Land management and natural hazard

Modélisation spatiale de la susceptibilité des versants aux mouvements de terrain

International audienceGIS are more and more used to model slopes landslides susceptibility. Among the different methods generally used, bivariate analysis are considered as the more efficient and robust techniques, particularly the Weight of Evidence technique. However, one major drawback of this technique is the problem of information redundancy between predictive variables. It needs an adapted strategy to reduce this conditional dependence problem. This paper presents a strategy to obtain good landslides susceptibility zonation without statistical problems at the 1/10 000 scale in a complex mountainous environment.Les SIG sont de plus en plus utilisés pour modéliser la susceptibilité des versants aux mouvements de terrain. Parmi les différentes méthodes utilisées, les techniques bivariées sont considérées comme les plus robustes et les plus souples à mettre en place, notamment la technique de la théorie de l'évidence. Cependant, l'inconvénient majeur de ce type de technique reste le problème de redondance d'information entre les variables prédictives, ce qui nécessite une stratégie adaptée pour régler le problème de dépendance conditionnelle. A travers une analyse de sensibilité sur les variables à modéliser et sur les variables prédictives, cet article présente une stratégie pour obtenir des cartes de susceptibilité réalistes et statistiquement acceptables pour une échelle du 1 /10 000éme dans un environnement montagneux complexe

Analyse spatiale de la susceptibilité des versants aux glissements de terrain

International audienceLes techniques d'analyse spatialisée par SIG sont de plus en plus utilisées pour évaluer la susceptibilité des versants aux glissements de terrain. Parmi ces méthodes l'analyse bivariée par théorie de l'évidence est considérée comme la plus robuste. Cependant, l'inconvénient principal de cette technique est le problème de redondance d'information entre variables prédictives. L'analyse bivariée par régression logistique, assez peu utilisée actuellement, donne des résultats prometteurs dans ce domaine sans nécessiter un travail d'évaluation préalable des données. Par une analyse de sensibilité sur les variables prédictives, cet article présente une comparaison de ces deux méthodes pour obtenir des cartes de susceptibilité réalistes et statistiquement acceptables pour une échelle du 1 /10 000e dans un environnement montagneux complexe