Survey of landslide activity in the Swiss Alps with ALOS PALSAR
Tazio Strozzi(1), Urs Wegmüller(1), Charles Werner(1), Andreas Wiesmann(1), Maurizio Santoro(1), Hugo Raetzo(2) and Reynald Delaloye(3)
(1) Gamma Remote Sensing, Wobstrasse 225, 3073 Gümligen, Switzerland
(2) Federal Office for Environment, -, 3003 Bern, Switzerland
(3) University of Fribourg, Chemin du Musée 4, 1700 Fribourg, Switzerland
PALSAR data acquired over the Swiss Alps since the summer of 2006 have been interferometrically analyzed for the survey of the activity of unstable slopes. According to the PALSAR Observation Strategy there are over our area of interest 1 to 2 interferometric observations per year in Fine beam Single polarization mode (HH polarization, 34.3 off-nadir angle, ascending orbit) and 2 to 3 interferometric observations per year in Fine beam Dual polarization mode (HH+HV polarizations, 34.3 off-nadir angle, ascending orbit). Differential interferometric analysis has been performed by use of high precision external Digital Elevation Models. The differential interferograms are employed for a large-scale motion survey, determining the position, extent, contour, and approximate velocity of unstable slopes. Acquisition time intervals from one cycle (46 days) up to one year are useful depending on data availability, displacement velocities, landcover and season. Results in the Swiss Cantons of Valais, Ticino, Bern and Grison will be discussed together with in-situ information and maps derived from ERS and ENVISAT satellite SAR data. The selected case studies represent a comprehensive data base with a range of different mass wasting phenomena in various environments, including deep-seated sliding processes in built-up and forested regions, and rock glaciers and push-moraines in alpine areas.