Investigating landslide-prone towns in Daunia (Italy) with PS interferometry

Persistent Scatterers Interferometry (PSI) and satellite radar imagery can be used to detect very slow displacements (mm-cm per year) of targets (PS) exhibiting coherent radar backscattering properties (mainly man-made structures). Here we present results of the PSI application to the Daunia Apennines, which include many hilltop towns affected by landslides. Examples from the towns Casalnuovo Monterotaro and Pietramontecorvino are used to illustrate that the interpretation of PS data on urbanised slopes can be diffi-cult, because their movements may arise from a variety of processes: i) volumetric strains within soils, ii) natural or anthropogenic subsidence or uplift, iii) settlement of engineering structures, iv) deterioration of man-made structures, v) extremely slow slope deformations that may or may not lead to failure. Where true landslide movements are detected, they likely regard long-term post-failure displacements involving clay-rich materials.