Land subsidence of natural transitional environments by satellite
radar interferometry on artificial reflectors
T. Strozzi, U. Wegmuller, C. Werner
Gamma Remote Sensing, Gumligen, Switzerland
P. Teatini
Dept. of Civil Environmental and Architectural Engineering,
University of Padova, Padova, Italy
L. Tosi
Institute of Marine Sciences, CNR, Venezia, Italy
Land subsidence is a widespread phenomenon, particularly relevant to transitional
environments, such as wetlands, deltas, and lagoons, characterized by low elevation with
respect to the mean sea level. Satellite synthetic aperture radar (SAR) interferometry offers
the possibility to effectively and precisely measure land displacements for dry surfaces or
anthropogenic structures, but difficulties arise in identifying long-term stable targets in
natural transitional regions. In order to improve the coverage of satellite SAR interferometry
in salt marshes within the Venice Lagoon (Italy), we installed a network of 57 Trihedral
Corner Reflectors (TCRs). The TCRs were monitored by ENVISAT ASAR and
TerraSAR-X acquisitions covering the time period from November 2006 to September
2011. The results show that the northern lagoon basin is subsiding at ~3 mm/yr and that the
central and southern portions are more stable. Larger subsidence rates, up to 6 mm/yr, are
measured where surficial loads, such as artificial salt marshes or embankments, rise above
the lagoon bottom. The accuracy of TerraSAR-X is greater than ENVISAT due to the
shorter wavelength and higher spatial resolution in relationship to the size of the TCRs. The
observations obtained in the Venice Lagoon indicate that SAR interferometry using a large
network of artificial reflectors is an effective and powerful methodology to monitor land
subsidence in transitional environments where the loss of elevation with respect to the mean
sea level can yield significant morphological changes to the natural environment.
