Combining L- and X-band SAR Interferometry to assess ground displacements in heterogeneous coastal environments:
The Po River Delta and Venice Lagoon, Italy
L. Tosi, C. Da Lio
Institute of Marine Sciences, CNR, Venezia, Italy
T. Strozzi
Gamma Remote Sensing, Gumligen, Switzerland
P. Teatini
Dept. of Civil, Environmental and Architectural Engineering,
University of Padova, Padova, Italy
From leveling to SAR-based interferometry, the monitoring of land subsidence in coastal
transitional environments significantly improved. However, the simultaneous assessment of the
ground movements in these peculiar environments is still challenging. This is due to the presence of
relatively small built-up zones and infrastructures, e.g., coastal infrastructures, bridges, and river
embankments, within large natural or rural lands, e.g., river deltas, lagoons, and farmland. In this
paper we present a multi-band SAR methodology to integrate COSMO-SkyMed and ALOS-PALSAR
images. The method consists of a proper combination of the very high-resolution X-band Persistent
Scatterer Interferometry (PSI), which achieves high-density and precise measurements on single
structures and constructed areas, with L-band Short-Baseline SAR Interferometry (SBAS), properly
implemented to raise its effectiveness in retrieving information in vegetated and wet zones.
The combined methodology is applied on the Po River Delta and Venice coastland, Northern Italy,
using 16 ALOS-PALSAR and 31 COSMO-SkyMed images covering the period between 2007 and
2011. After a proper calibration of the single PSI and SBAS solution using available GPS records,
the datasets have been combined at both the regional and local scales. The measured displacements
range from ~0 mm/yr down to ~35 mm/yr. The results reveal the variable pattern of the subsidence
characterizing the more natural and rural environments without losing the accuracy in quantifying
the sinking of urban areas and infrastructures. Moreover, they allow improving the interpretation of
the natural and anthropogenic processes responsible for the ongoing subsidence.
