Interpretation of Aerial Photographs and Satellite SAR Interferometry for the Inventory of Landslides

Tazio Strozzi,Christian Ambrosi,Hugo Raetzo

doi:10.3390/rs5052554

Abstract

An inventory of landslides with an indication of the state of activity is necessary in order to establish hazard maps. We combine interpretation of aerial photographs and information on surface displacement from satellite Synthetic Aperture Radar (SAR) interferometry for mapping landslides and intensity classification. Sketch maps of landslides distinguished by typology and depth, including geomorphological features, are compiled by stereoscopic photo-interpretation. Results achieved with differential SAR interferometry (InSAR) and Persistent Scatterer Interferometry (PSI) are used to estimate the state of activity of landslides around villages and in sparsely vegetated areas with numerous exposed rocks. For validation and possible extension of the inventory around vegetated areas, where InSAR and PSI failed to retrieve displacement information, traditional monitoring data such as topographic measurements and GPS are considered. Our results, covering extensive areas, are a valuable contribution towards the analysis of landslide hazards in areas where traditional monitoring techniques are sparse or unavailable. In this contribution we discuss our methodology for a study area around the deep-seated landslide in Osco in southern Switzerland.

Highlights

Hazards due to slope instabilities affect about 6% of the Swiss territory [1,2]
In this contribution we discuss our combined approach for landslide inventory based on aerial photographs and Synthetic Aperture Radar (SAR) interferometry for a region along the northern flank of the Leventina valley above Faido, which is affected by one of the largest deep-seated slope movements in Switzerland [21,22]
The identification of ground motion from Interferometric Synthetic Aperture Radar (InSAR) and Persistent Scatterer Interferometry (PSI) complements the geomorphological information collected by photo-interpretation well

Summary

Introduction

Hazards due to slope instabilities affect about 6% of the Swiss territory [1,2]. The estimated annual cost for protection against landslides amounts to CHF 2.9 billion, which is about 0.6% of the gross domestic product or equivalent to CHF 400 per inhabitant [3]. InSAR and PSI displacement information can be integrated with previous landslide maps to reach a more complete and substantiated conclusion about the state of activity of slope instabilities [13,14,15,16,17,18,19,20] In this contribution we discuss our combined approach for landslide inventory based on aerial photographs and SAR interferometry for a region along the northern flank of the Leventina valley above Faido, which is affected by one of the largest deep-seated slope movements in Switzerland [21,22]. The lower half of the slope has a strongly convex profile resulting from numerous large rotational and translational slides, including that of Osco (Figure 2), whose activity has been known for a long time and of which we commonly refer to the deep-seated landslide

Aerial Photography Interpretation

Satellite SAR Interferometry

Landslides Inventory

Findings

Conclusions