First delimitation of areas affected by ground deformations in the Guadalfeo River Valley and Granada metropolitan area (Spain) using the DInSAR technique

Abstract A Differential Interferometric SAR (DInSAR) analysis of terrain displacements in the province of Granada (southern Spain) is presented here for two different study zones. The first zone concerns the Guadalfeo River Basin, where abundant landslides and unstable slopes were previously identified and inventoried on a GIS application. However, no instrumental quantification of landslide activity was available. Considering morphological criteria and field observations, these deep-seated landslides were considered to be “dormant” or moving extremely slowly. The second study zone corresponds to the Granada metropolitan area, where no previous information was available on any vertical movement. The analysis was based on ERS1 and ERS2 images, covering the period from 1993 to 2000. By using DInSAR, we made an initial qualitative assessment of movements on landsliding slopes in the Guadalfeo River Basin and also vertical land movements in the alluvial Quaternary sediments to the west and south of the Granada metropolitan area. The terrain instability assessment resulting from this research shows maximum annual velocities along the SAR line of sight (LOS) of 6 mm/yr for the Tablones landslide, and up to 13 mm/yr for the Albunuelas village; where progressive differential settlement processes were established as the origin of the movement. In the case of the Granada metropolitan area, two sites were detected with subsidence affecting two villages: Santa Fe, located in the western part of the area, with an estimated average velocity of 8 mm/yr and Otura in the south of the area, with maximum velocities of 12 mm/yr. A description of geological features of the different sites, showing LOS ground displacement, is presented with a discussion of the application of the rates to landslide-activity assessment found, local ground conditions, or exploitation of subterranean water in urban areas.