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Potential and limitation of SAR Interferometry for landslides study in the French Alps and Pyrenees

Christophe Delacourt(1) and Cristina Squarzoni(2)

(1) UCBL & ENS Lyon, Bat Geode 2 Rue Raphael Dubois, 69622 Villeurbanne, France
(2) ucbl & ENS Lyon, bat Geode, 69622 Villeurbanne, France

Abstract

Study of the spatial and temporal evolution of the velocity field is a way to better understand the parameters of control of slow landslide (some centimeters per week over several years). A multiyear trend of velocity variation is superimposed to seasonal meteorological variation, and to episodic events. A multitemporal and multi scale study is required to decipher the signature of each causes. Kinematic studies are usually realized by punctual techniques (levelling, lasermeter, GPS) which are not able to assess spatial heterogeneities. SAR interferometry is a powerful tool, providing an image representing the motion. However, in the past studies, only few succeeded applications of SAR interferometry for landslides have been carried out. In the present work, a quantitative and comparative analysis of potential and limitations of SAR Interferometry for landslides study in French Alps and French Pyrenees is achieved. We focus on the quantification of severe limitations : a dense vegetation cover leading to decorrelation, high variation of topography, and deformation rate leading to loss of coherence. Then, a landslide called “La Valette”, placed in the southern French Alps is studied using 15 differential interferogramms produced from SAR images acquired by ERS 1 and ERS 2 satellites between 1991 and 1999. Velocity maps of “La Valette” landslide have been established. Four domains characterized by their own velocity field have been detected. Three of them can be distinguished from aerial photographs and field analysis. Slow velocity of a resistive bar located near the top of the landslide has been detected on SAR interferogramms. Between 1991 and 1996, evolution of the limits of the landslide has been observed both in the upper and in the lower part, by a back erosion corresponding with the main scarp and a progress of the main body of the landslide. The average velocity of the landslide between 1991 and 1999 decreased from 1cm/day to 0.2cm/day in agreement with ground based measurements.

 

Full paper

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry