Contribution of remote sensing to landslide integrated monitoring system: the use of ground-based SAR interferometry in Austrian Alps

In mountainous regions, such as alps, rockfalls are one of the most common geomorphological processes representing one of major causes of landslide fatalities and economic losses. According to GEORIOS database (GEORIsiken ÖSterreich), in Austria more than 30,000 gravitational mass movements have been counted, 19% of which are rock falls. In this context, the monitoring of parameters concerning triggering factors (eg. temperature, rainfall, pore pressure) and displacement (deep and shallow), plays a key role in the preparation of actions for risk reduction. The present work illustrates the integrated monitoring system of Ingelsberg in Bad Hofgastein, where a highly hazardous landslide in Salzburg Land is located. A 15-months monitoring campaign (March 2013 – July 2014) was realized through the use of several monitoring instrumentations such as 5 bar extensometers, 2 weather stations and 3 cameras (Romeo et al., 2014). In this framework, it was also carried out an accurate monitoring of the surface displacement, with high temporal and spatial resolution, by using terrestrial SAR interferometry technique, constituting the first long-term GBInSAR (Groung-Based Interferometric Synthetic Aperture Radar) measurements implemented in Austria. During the monitoring campaign, a main rockfall occurred at the end of April 2013 that involved up to 40 m3 of rocks. Thanks to the large amount of data, it was possible to analyze the pre-failure days in order to detect possible factors that contributed to the collapse: surface displacement given by GB-InSAR was compared with displacement measurements in depth given by extensometers and results are discussed taking into account meteorological conditions antecedent the rockfall triggering. The integration between conventional monitoring methods and new technologies such as GB-InSAR was very useful for the comprehension of landslide processes, particularly in rock slope where, for example, by comparing displacement time series with other parameters as temperature and rainfalls, it is possible to identify the most susceptible blocks to collapse (Mazzanti, 2014). In addition, a multi-instrumental approach is essential to investigate movements both in surface and in depth and the use of different monitoring techniques allows to perform a cross analysis of the data, to check the data quality enhancing the reliability of the entire system. This is of paramount significance in early warning systems. Romeo S., Kieffer D.S. & Di Matteo L. 2014. The Ingelsberg landslide (Bad Hofgastein, Austria): description and first results of monitoring system (GBInSAR technique). Rend. Online Soc. Geol. It., 32, 24-27. Mazzanti P., Bozzano F., Brunetti A., Esposito C., Martino S., Prestininzi A., Rocca A. & Scarascia Mugnozza G. 2014. Terrestrial SAR Interferometry Monitoring of Natural Slopes and Man-Made Structures. In: Lollino G. et al. Eds., Engineering Geology for Society and Territory, 5, 189-194. Springer Int. Pub.