Sensing the land subsidence within the Venice Lagoon
by Interferometric Point Target Analysis
P. Teatini
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
L. Tosi, L. Carbognin
Institute of Marine Sciences, CNR, Venezia,
Italy
T. Strozzi
Gamma Remote Sensing, Muri (BE), Switzerland
G. Cecconi
Servizio Ingegneria, Consorzio Venezia Nuova, Venezia, Italy
R. Rosselli
Sistema Informativo, Magistrato alle Acque di Venezia, Venezia, Italy
V. Volpe
Ispettorato Laguna, Magistrato alle Acque di Venezia, Venezia, Italy
ABSTRACT
Land subsidence is a severe geologic hazard threading the lowlying coastal
areas worldwide. Monitoring land subsidence has been significantly improved
over the last few years by space borne earth observation techniques based on
SAR (Synthetic Aperture Radar) Interferometry. Within the INLET Project,
funded by Magistrato alle Acque di Venezia - Venice Water Authority (VWA) and
Consorzio Venezia Nuova (CVN), we have used the Interferometric Point Target
Analysis (IPTA) to characterize the ground displacements within the Venice
Lagoon. IPTA measures the movement of backscattering objects (point targets,
PT) at the ground surface which persistently reflect radar signal emitted by
the SAR antenna. For this study 80 ERS-1/2 and 44 ENVISAT scenes recorded from
1992 to 2005 and from 2003 to 2007, respectively, have been processed by IPTA.
High reliable land subsidence data have been detected for thousands of PT
located on the lagoon margins, along the littorals, in major and small islands,
and on single anthropogenic structures scattered within the lagoon. On the
average, land subsidence ranges from less than 1 mm/year to 5 mm/year, with
some PT that exhibit values also larger than 10 mm/year depending on both the
local geologic conditions and anthropogenic activities. A network of few tens
of artificial square trihedral corner reflectors (TCR) has been established
before summer 2007 to monitor land subsidence in the inner lagoon areas where
natural reflectors completely lack (e.g., on the salt marshes). The first
interferometric results on the TCR appear very promising.
