USING DINSAR INTERFEROMETRY OF RADAR SATELLITE IMAGES IN QUANTITATIVE ASSESSMENT OF LANDSLIDE ACTIVITY IN THE GUADALFEO RIVER VALLEY (GRANADA, SOUTH OF SPAIN)

P. Fernandez, C. Irigaray, R. El Hamdouni, J. Jimenez, J. Chacon

University of Granada, Departament of Civil Engineeering, Granada, Spain

pazferol@ugr.es

A SAR (DInSAR) analysis of RADAR satellite images of landslides in the Guadalfeo River basin (South of Granada, Spain) is here presented based on ERS1 and ERS2 images following a methodology with two main steps: a first basic treatment of SLC focused images to obtain differential interferograms with the wrapped phase using a Digital Elevation Model (DEM) of the study zone. The second step includes elaborations of theses interferograms with a specific DInSAR technique to asses the average annual velocity in the landslide masses. The obtained results are first evidences of the activity of these landslides which are potentially affecting villages (Albuñuelas, 1100 inhabitants; Lanjarón, 3750 inhabitants) or the Guadalfeo river with is over villages as Vélez de Benaudalla, 2800 and Motril, 56600, which could be affected by flash flooding after a landslide dam failure situation. Despite the interest of assessing the risks derived from the activity of these landslides no instrumentations were available and from these the great interest of using DInSAR interferometry techniques may be easily understood.

The landslide activity assessment resulting from these research shows annual average vertical velocities for the period 1993-2000 of 6 mm/yr for Tablones landslide, 7 mm/yr for the Lanjarón landslide and up to 13 mm/yr for the Albuñuelas landslide.

The quantitative assessment of landslide activity is introduced in a GIS application to landslide hazard and risk mapping of the Guadalfeo River Valley in which a database of landslides, along with digitized information about element of the territory and the analysis of correlation between determinant factors of the slope stability are combined with triggering data concerning rainfall, earthquake activity and also landslide activity. The main outputs of the GIS application are in terms of susceptibility, hazard and risk maps of the region at variable scales from a pixel resolution of 10 m.