No abstract

Abstract:The active Sé chilienne landslide (Isè re, France) has been continuously monitored by tacheometry, radar and extensometry devices for 25 years. Indeed, if the 3 mil. m 3 of rocks in the active zone named -Ruines‖ fell down, the debris would dam the

No abstract

The National Road RN 91 has been threatened for about twenty-five years by a huge landslide, located 25 km south-east to the town of Grenoble (France). If several million cubic meters of rock fall down, the debris will dam the valley. Then the failure of the dam by overtopping and rapid erosion might result in a catastrophic flood and dramatic consequences for human life, environment and economy throughout the valley. The paper presents the hazard assessment based on geological and hydrological surveys, including small scale hydraulic tests, as well as the risk evaluation that has been performed. The risk management relies first upon a high level monitoring and an emergency plan; various mitigation strategies have been considered.

International audienceThe slope movement at Sedrun (Switzerland) has been studied with ortho-rectified images. Displacement maps compiled for two periods (1973–1990 and 1990–2003), based on a correlation of the aerial images indicate maximum average slope movements of 60 cm/year, similar to those obtained by traditional photogrammetry over the period 1973–1990. The limits of the most active zones determined by image correlation correspond to those obtained by fieldwork. Comparison of the two displacement maps shows an acceleration of the instability of 150% since 1990. This paper demonstrates the value of using more than one technique to help understand the evolution of this long-term instability. Le mouvement de versant de Sedrun (Suisse) a été étudié par corrélation d'images aériennes ortho-rectifiées. Des cartes de déplacements de ce mouvement de versant ont été déterminées sur deux périodes (1973–1990 et 1990–2003). Le mouvement du versant de Sedrun atteint une vitesse de 60 cm/an au maximum. Les valeurs de déplacements ainsi déterminées correspondent aux déplacements obtenus par photogrammétrie classique sur la période 1973–1990. Les limites des zones les plus actives correspondent aux observations de terrain alors que d'autres zones, bien que fort remarquables, semblent moyennement affectées. La comparaison des deux cartes d'amplitudes de déplacements montre une accélération de l'instabilité de 150% à partir de 1990. La corrélation optique à partir d'images aériennes d'archives a montré sa capacité à renseigner l'évolution de cette instabilité à long terme