Peatland subsidence in the Venice watershed
L. Carbognin, P. Teatini, L. Tosi, A. Tomasin
Institute of Marine Sciences, CNR, Venezia, Italy
T. Strozzi
Gamma Remote Sensing, Gumligen, Switzerland
ABSTRACT
Relative sea level rise (RSLR), that has been occurred along the entire coastal areas
of the Northern Adriatic Sea, includes land subsidence, both natural and man-induced,
and eustacy. Their combined effect has produced relative ground settlements ranging
from centimetres to meters. RSLR represents one of the geologic hazards threatening
the low-lying coast. Recent progresses made in understanding these two processes
are presented. Synthetic Aperture Radar (SAR) interferometry has significantly
improved the knowledge of actual land subsidence. In particular, comprehensive maps of
the vertical displacements occurred over the period 1992-2009 in the region between
Venice and Ravenna reveal a significant spatial variability, ranging from a slight 1
to 2 mm•yr-1 uplift, to a serious subsidence of more than 15
mm•yr-1. The availability of tide gauge data in Trieste, Venice,
and Ravenna allows accurate assessment and meaningful observations on sea level change.
The period 1896-2006 is characterized by an average rise of 1.2 ± 0.1
mm•yr-1. The analyses here performed show that a time series at least
50 yr long must be used to obtain statistically
significant results and reliable trend, due to the 7-8 year pseudo-cyclicity,
recorded at many Mediterranean coastal stations. In Venice and Ravenna the influence
of land subsidence on the RSLR amounts to 57% and 85%, respectively. This
percentage has been estimated in 95% at the Po Delta.
