Investigation of Subsidence in the Manfredonia Gulf (Southern Italy) Through Multitemporal DInSAR Techniques

In the last decades, the coast of the Apulia Tavoliere plain has been subject to a considerable retreat. During strong hydrodynamic and meteorological events, sea waters penetrate deeply inland. Such phenomena, to-gether with the presence of failure damages over an-thropogenic structures, indicate the presence of subsi-dence over an extended area. To analyze the recent evolution and rates of occurrence of the phenomenon, Persistent Scatterers Interferometry (PSI) techniques have been applied, to obtain millimetric displacement maps from series of radar interferograms. 103 ERS-1/2 and ENVISAT scenes have been analysed, with acqui-sition dates spanning the interval 1995-2000 (ERS) and 2003-2008 (ENVISAT), respectively. The analysis is restricted to objects characterized by strong radar re-turn signals, generally coinciding with man-made fea-tures. The rural nature of the investigated area requires processing independently small patches on urban cen-tres. Nevertheless, taking into account indirect observa-tions and ground truth, a coherent picture emerges. Re-sults indicate the presence of deformations affecting the entire temporal interval analysed, spatially distrib-uted to form a "bowl" centered on the Ippocampo vil-lage with average rates exceeding 20 mm/y and an in-creasing trend in the most recent years.