Abstract
Slope instabilities are one of the most important geo-hazards in terms of socio-economic costs. The island of La Réunion (Indian Ocean) is affected by constant slope movements and huge landslides due to a combination of rough topography, wet tropical climate and its specific geological context. We show that remote sensing techniques (Differential SAR Interferometry and correlation of optical images) provide complementary means to characterize landslides on a regional scale. The vegetation cover generally hampers the analysis of C–band interferograms. We used JERS-1 images to show that the L-band can be used to overcome the loss of coherence observed in Radarsat C-band interferograms. Image correlation was applied to optical airborne and SPOT 5 sensors images. The two techniques were applied to a landslide near the town of Hellbourg in order to assess their performance for detecting and quantifying the ground motion associated to this landslide. They allowed the mapping of the unstable areas. Ground displacement of about 0.5 m yr-1 was measured.
Highlights
IntroductionDue to specific geological and climatic conditions, landslides are a major hazard affecting the island of La Réunion in the Indian Ocean [4, 5]
Landslides are a common disturbance in tropical mountainous areas [1,2,3]
We investigate the Hellbourg landslide displacements in La Réunion Island by integrating both JERS-1 and RADARSAT Differential Synthetic Aperture Radar (SAR) interferometry (DInSAR) with the results of the correlation of optical aerial and SPOT 5 images
Summary
Due to specific geological and climatic conditions, landslides are a major hazard affecting the island of La Réunion in the Indian Ocean [4, 5]. The Hellbourg landslide in the Salazie Circle has been monitored by GPS for several years on regularly revisited points. It represents a serious hazard for inhabited sectors and it could have an impact on buildings, roads and population. The speed of the landslide has a nearly linear evolution with time according to the GPS measurements performed during the period 1997–2000 by the Regional Geological Survey of la Réunion Island [6]. The averaged displacement rate is 0.5 m·y-1
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