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| Titel |
Large networks of artificial radar reflectors to monitor land subsidence in natural lowlying coastal areas |
| VerfasserIn |
Luigi Tosi, Tazio Strozzi, Pietro Teatini |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250100114
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| Publikation (Nr.) |
 EGU/EGU2014-16000.pdf |
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| Zusammenfassung |
| Deltas, lagoons, estuaries are generally much prone to land subsidence. They are also very
sensitive to land lowering due to their small elevation with respect to the mean sea level, also
in view of the expected eustatic sea rise due to climate changes. Land subsidence can be
presently monitored with an impressive accuracy by Persistent Scatterer Interferometry (PSI)
on the large megacities that are often located on lowlying coastlands, e.g., Shanghai (China)
on the Yangtze River delta, Dhaka (Bangladesh) on the Gange River delta, New Orleans
(Louisiana) on the Mississippi river delta. Conversely, the land movements of the portions
of these transitional coastlands where natural environments still persist are very
challenging to be measured. The lack of anthropogenic structures strongly limits the use
of PSI and the difficult accessibility caused by the presence of marshlands, tidal
marshes, channels, and ponds yield traditional methodologies, such as levelling and
GPS, both time-consuming and costly. In this contribution we present a unique
experimental study aimed at using a large network of artificial radar reflectors to
measure land subsidence in natural coastal areas. The test site is the 60-km long, 10-15
km wide lagoon of Venice, Italy, where previous PSI investigations revealed the
lack of radar reflectors in large portions of the northern and southern lagoon basins
(e.g., Teatini et al., 2011). A network of 57 trihedral corner reflectors (TCRs) were
established between the end of 2006 and the beginning of 2007 and monitored by
ENVISAT ASAR and TerraSAR-X acquisitions covering the time period from
2007 to 2011 (Strozzi et al., 2012). The application has provided general important
insights on the possibility of controlling land subsidence using this approach. For
example: (i) relatively small-size (from 0.5 to 1.0 m edge length) and cheap (few
hundred euros) TCRs suffice to be clearly detectable from the radar sensors because of
the low backscattering intensity of the surrounding area; (ii) the network must be
established resembling a sort of levelling benchmark network, i.e. with the TCRs placed
keeping to a value of about 1.0-1.5 km the maximum distance between the TCRs or
between an “artificial” and the adjacent “natural” reflectors to reliably resolve the
radar phase ambiguities in the presence of atmospheric artifacts. Moreover, our
experiment provided new information in order to improve the knowledge of the
regional and local processes acting in the Venice Lagoon. We found that the northern
basin of the lagoon is subsiding at a rate of about 3-4 mm/yr, while the central
and the southern lagoon regions are more stable. At the local scale, i.e., the scale
of the single salt marshes, significant differences have been detected depending,
for example, on the nature and the architecture of Holocene deposits (Tosi et al.,
2009).
Acknowledgments.
This work was supported by Magistrato alle Acque di Venezia-Venice Water Authority
(VWA) and Consorzio Venezia Nuova (CVN) through the INLET Project and partially
developed within the RITMARE Flagship Project (CNR-MIUR), Action 2 (SP3-WP1).
TERRASAR-X data courtesy COA0612, © DLR.
References.
Teatini, P., Tosi, L., Strozzi, T., Carbognin, L., Cecconi, G., Rosselli, R., &
Libardo, S. (2012). Resolving land subsidence within the venice lagoon by persistent
scatterer SAR interferometry. Physics and Chemistry of the Earth, 40-41, 72-79, doi:
10.1016/j.pce.2010.01.002.
Strozzi, T., Teatini, P., Tosi, L., Wegmüller, U., & Werner, C. (2013). Land subsidence
of natural transitional environments by satellite radar interferometry on artificial
reflectors. Journal of Geophysical Research F: Earth Surface, 118(2), 1177-1191, doi:
10.1002/jgrf.2008.
Tosi, L., Rizzetto, F., Zecchin, M., Brancolini, G., & Baradello, L. (2009).
Morphostratigraphic framework of the venice lagoon (italy) by very shallow water
VHRS surveys: Evidence of radical changes triggered by human-induced river
diversions. Geophysical Research Letters, 36(9), doi: 10.1029/2008GL037136. |
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