A century of land subsidence in Ravenna, Italy
P. Teatini, M. Ferronato, G. Gambolati,
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
W. Bertoni
Ravenna Geological Service, Ravenna, Italy
M. Gonella
Med Ingegneria S.r.l., Ferrara, Italy
ABSTRACT
Over the last century the Ravenna area has been affected by a widespread land subsidence
process of both natural and anthropogenic origin which has become a matter of increasingly great
concern. Land settlement, initially of the order of a few mm/year, dramatically increased
up to 110 mm/year after World War II primarily due to groundwater pumping and,
subordinately, gas production from a number of deep on-shore and off-shore reservoirs.
Spirit leveling was carried out in the area of the Ravenna Municipality by various
authorities and agencies ever since the end of the nineteenth century using an
increasingly refined network of benchmarks. The available information, spanning the
time interval from 1897 to 2002, has been implemented and homogenized
into a Geographic Information System (GIS) system. Measurements processed by kriging
provide the pattern of the subsidence rates over the municipal territory during eight
sub-periods. The reliability of data processing is discussed for both magnitude and
areal distribution of the occurrence, showing a pronounced nonlinear behavior in time,
as related to the major responsible factors. Cumulative land subsidence approaches
almost 1 m over more than one third of the municipality area including the city and a
significant fraction of the coastland, with peaks larger than 1.5 m
over a 10 km2 zone located between the historical center and the coastline.
Most recent records show that at present the mainland appears to be substantially stable,
whereas some coastal areas are still subsiding at a rate of about 10 mm/year with a
significant threat to the environment and the infrastructures as well, although to a
lesser extent than in the past decades.
