Advanced monitoring techniques for mapping land displacement on the Venice coastland with satellite SAR data
G. Bitelli, L. Vittuari
Dept of Civil, Environmental and Materials Engineering, University of Bologna, Bologna, Italy
F. Bonsignore
ARPA Emilia-Romagna, Bologna, Italy
L. Carbognin, L. Tosi
Institute of Marine Sciences, CNR, Venezia, Italy
A. Ferretti
Tele-Rilevamento Europa S.r.l. (TRE), Milano, Italy
T. Strozzi
Gamma Remote Sensing, Gumligen, Switzerland
P. Teatini
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
ABSTRACT
The northern Adriatic coastal area, Italy (from the Veneto region northward, and to the Romagna
region to the south), is characterized by low-lying environments such as lagoons, e.g. those of Venice and of
the Valli di Comacchio, wetlands and deltas, such as that of the Po River delta, and reclaimed farmland and
beaches subjected to marked anthropogenic pressure. The coastal area is characterized by an elevation
generally well below the mean sea level (down to -4 m m.s.l.) and never exceeds 2 m above m.s.l. Maninduced
land subsidence has greatly affected the whole coastal area over the 20th century, and especially
from the 1950s and the 1970s, when over-exploitation of subsurface fluids was responsible for the
occurrence of general lowering. Although the sinking rates have significantly decreased over the last
decades, land subsidence is still a process threatening the entire coastal environment. In this study we report
a recent investigation aimed at mapping the vertical displacements recorded in the period 1992-2000 on the
20-30 km wide and 250-km long coastal area from the Tagliamento River to the north, to the town of
Rimini to the south. Measurements have been carried out by Persistent Scatterer Interferometry (PSI) using
levelling and GPS records to reference the interferometric solution. The results identify the variability of the
ground movements that are presently occurring along the northern Adriatic coastline. Substantially stable
areas, the most important of which are the cities of Venice and Ravenna and their surroundings, contrast
with subsidence rates of more than 10 mm/year recorded in some parts of the Po River delta and to the
south. The observed land displacements have been associated with the geological features of the study
region, i.e. tectonics and differential consolidation of the Middle-Upper Pleistocene and Holocene deposits,
and to anthropogenic activities, mainly groundwater withdrawal from the Upper Pleistocene-Holocene
alluvial deposits and more locally peatland oxidation in reclaimed areas and gas exploitation from
Plio-Pleistocene reservoirs.
