Sébastien Gourdier

Bio: Sébastien Gourdier is an academic researcher. The author has contributed to research in topics: Geology & Landslide. The author has an hindex of 1, co-authored 2 publications receiving 9 citations.

Improvement of landslide hazard assessments for regulatory zoning in France: STATE–OF–THE-ART perspectives and considerations

Abstract: In France, in the context of regulatory mapping (PPRNs –Prevention Plans of Natural Risk based on French regulatory rules), landslide hazard assessment follows an empirical approach and uses basic available data. Therefore, the results are closely linked to the quality of the expertise and divergent opinions may arise in some specific cases. In recent years, numerical approaches using GIS, the availability of new databases, the development of new acquisition tools in the field and web visualization services have improved the knowledge of phenomena and different landslide-prone areas. Numerical approaches using GIS, that allow the transparency and traceability of results, have various levels of complexity and require different quantities of input data. However, they are often neglected by experts and new data and tools are not currently used to develop regulatory mapping documents. Numerous scientific examples show that these numerical approaches, web services and new tools can be a significant help in improving knowledge and provide a credible alternative to the expert approach, even in a regulatory context such as a PPRN. Thus, through this synthesis carried out as part of the regulatory mapping of landslide hazards and risks in France, a state-of-the-art spatial assessment of current landslide hazards is performed. The new tools and newly available databases to support this type of analysis are then described. Finally, the perspectives and limitations of alternative approaches and new tools and data are discussed, leading to some considerations for the improvement of the current method of producing landslide hazard maps for PPRNs in France.

Modèle de réponse des sols argileux à la sécheresse : application au site instrumenté de Mormoiron

Abstract: En France, durant les trois dernieres decennies, plusieurs periodes de deficit pluviometrique ont ete a l'origine de nombreux dommages aux habitations individuelles, particulierement vulnerables au phenomene de retrait-gonflement des argiles. Afin de mieux comprendre ce phenomene, le BRGM a instrumente un site dans le Vaucluse depuis 2004, pour mesurer en continu et a differentes profondeurs les teneurs en eau des sols argileux, ainsi que les deplacements verticaux associes. Sur les sept premiers metres du site d'etude, essentiellement constitues d'argiles plastiques vertes a smectite, ont ete implantes 27 capteurs d'humidite, 6 extensometres, un pluviometre et une centrale d'acquisition. Avant toute analyse ou utilisation comme donnees d'entree d'un modele, un pretraitement s'avere necessaire, d'autant plus que certaines chroniques de teneurs en eau peuvent etre entachees de mesures parasites. Le pretraitement des donnees est effectue en trois etapes. Dans un premier temps les valeurs hors intervalles de mesure sont exclues des chroniques. Puis est applique un filtre statistique, base sur l'analyse de la mediane et des quantiles. Enfin on effectue un filtrage statistique, base sur l'analyse de la transformee de Fourier. Un modele analytique multicouche unidimensionnel a ete developpe dans le but de reproduire les deplacements dus au phenomene de retrait-gonflement des argiles, en terrain nu ou sous un bâtiment. Il est base sur l'utilisation de la courbe de retraction, courbe caracteristique du sol argileux etudie etablissant une relation entre la teneur en eau et l'indice des vides. Le modele est calibre en l'appliquant aux chroniques de teneurs en eau volumique enregistrees sur le site instrumente de Mormoiron, pour reproduire les deplacements verticaux observes a l'aide des extensometres.

Earthquake-induced landslides susceptibility assessment: A review of the state-of-the-art

Abstract: Earthquake-induced landslides (EQL) can take a heavy toll on people's life and properties, thus attracting extensive attention of the geosciences community. Carrying out earthquake-induced landslide susceptibility assessment (EQLSA) is of great significance to the prevention and reduction of such disasters as well as recovery and reconstruction in affected areas. This study examined the research status of earthquake-induced landslide susceptibility using data aspects, variable model types, and evaluation scales. To begin, we will discuss the current state and shortcomings of the earthquake landslide inventory, as well as the common landslide influencing factors that serve as the foundation for EQLSA. Then we presented the most common EQLSA methods and discussed their advantages and disadvantages. Meanwhile, we used CiteSpace to visually analyze papers in the Web of Science database with the theme word "landslide susceptibility" from 2008 to 2020. Each paper is summarized in terms of the evaluation scale. Finally, the research difficulties of landslide susceptibility in spatial scale, qualitative and quantitative problems, and spatial representation of landslide information are discussed, and future research directions are suggested.

Mapping Landform and Landslide Susceptibility Using Remote Sensing, GIS and Field Observation in the Southern Cross Road, Malang Regency, East Java, Indonesia

Abstract: There has been an increasing trend of land area being brought under human’s use over time. This situation has led the community to carry out land-use development activities in landslide hazard-prone areas. The use of land can have a positive impact by increasing economic conditions, but it can have negative impacts on the environment. Therefore, this study aimed to identify the landslide hazard, focusing on the development of a landform map to reduce the risk of landslide disaster in JLS, Malang Regency. The integration of remote sensing and geographic information systems, as well as field observation, were used to create a landform map and a landslide susceptibility map. Using the geomorphological approach as a basic concept in landform mapping, the morphology, morphogenesis, and morphoarrangement conditions were obtained from the remote sensing data, GIS, and field observation, while morphochronological information was obtained from a geological map. The landslide susceptibility map was prepared using 11 landslide conditioning factors by employing the index of entropy method. Thirty-nine landform units were successfully mapped into four landslide susceptibility classes. The results showed that the study area is dominated by a high level of landslide susceptibility with a majority of moderate to strongly eroded hill morphology. It also reaffirms that landform mapping is a reliable method by which to investigate landslide susceptibility in JLS, Malang Regency.

Infinite slope stability model and steady-state hydrology-based shallow landslide susceptibility evaluations: The Guneysu catchment area (Rize, Turkey)

Abstract: The main purpose of this study is to investigate shallow landslide susceptibility by considering the infinite slope stability model and steady-state hydrological conditions. The prediction performance of the Stability Index Mapping (SINMAP) carried out by considering the mechanical and hydrological parameters and soil thickness values for different residual soils derived from different geological formations was evaluated. For this purpose, comprehensive geotechnical site investigations were conducted in the Guneysu catchment area located at the east of Rize in the Eastern Black Sea region of Turkey, where shallow landslides are frequently observed within the residual levels developed as a result of decomposition of magmatic rocks. The research was performed in four stages: (i) The general characteristics of the region were examined; (ii) detailed investigations were carried out for the preparation of shallow landslide inventory of the Guneysu catchment area; (iii) to reveal the mechanical and hydrological characteristics of the residual soils, disturb and undisturbed samplings were carried out, and geophysical investigations were performed; (iv) as the last stage, shallow landslide susceptibility was assessed by implementing the SINMAP mathematical model. As a result, the average accuracy value of the models produced to predict shallow landslide initiation in the region was obtained to be 96.7%. Considering the statistics achieved in this research, it is realized that the differentiation of soil material increases the model prediction capacity. Additionally, pre-evaluations of the mechanical and hydrological characteristics of the residual soils also increase the estimation performance.

Optimized Landslide Susceptibility Mapping and Modelling using PS-InSAR technique: A case study of Chitral Valley, Northern Pakistan

Abstract: Chitral valley lies in the eastern Hindu Kush range, one of the hotspot of landslide activities that leads to loss of lives and economy. Comprehensive landslide inventory and Landslide susceptibili...