A landslide forecasting model using ground based SAR data: The Portalet case study

This paper presents a kinematic study of the Portalet landslide (Sallent de Gállego, Central Spanish Pyrenees), which was triggered by the construction of a big parking area at the toe of the slope. A description of the landslide from a geomorphological point of view is first introduced. The measurements of displacement performed by conventional (total station, inclinometers and differential GPS) and advanced (GB-SAR) ground monitoring techniques are presented and GB-SAR and DGPS datasets are compared. The correlation between measured displacements and rainfall series indicates that the landslide is very sensitive to rainfall. The continuous GB-SAR measurements from the 5th of October 2006 to the 21st of November 2006 at a rate of 1/h were used to calibrate a simple 1D infinite model by back analysis. The model includes a viscoplastic behaviour and takes into account directly the known daily rainfall intensity and the dissipation of the excess pore-fluid through a simple consolidation equation. Prediction was made in an extended period of time, from May 2006 to July 2007, and compared to the DGPS measurements.