ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

Together with the Geomorphological Map of the Po Plain
at a scale of 1:25,000, the Map of the relief and vertical
movements of the Po Plain has been produced at the same
scale. Both maps were coordinated by Prof. G. Castiglioni
(Department of Geography of the University of Padua)
and the authors from 10 Universities and other scientific
institutions in northern Italy.
Apart from showing the altimetry of the Po Plain by means
of depicting the contour lines, this second map presents a
synthesis of the ground movements which have been recorded
since 1897. These movements are not only due to neotectonics
and natural subsidence but above all to phenomena
of artificial subsidence. The latter were mainly caused
by the drainage of water for agricultural, industrial and
civil uses, the extraction of water containing methane, the
hydraulic reclamation carried out between 1860 and 1970,
and the artificial control of the ground water.
The impact of this subsidence is very marked; in fact it has
been the main cause of the presence of vast depressions in
the part of the plain which lies closest to the sea, impeding
the runoff of surface water, and in particular modifying the
slopes of the canals for the drainage of rain water, thus
compromising the functionality of numerous pumping stations
present in this area and impeding the distribution of
the irrigation water. In addition the subsidence raises the
height of the ground water in the cultivated fields and provokes
the infiltration of sea water into the ground water.
On the coast it causes the beaches to retreat and increases
the danger of flooding.
The study of the vertical movements of the ground was based
on the data resulting from the levelling surveys carried
but by the Istituto Geografico Militare and the Direzione
del Catasto. A first insert of the map shows the subsidence
for the period between 1897 and 1957 (Arca & Beretta,
1985). It then shows the data for the following decades, up
to 1990: the latter study, which is largely unpublished, was
carried out by M. Bondesan, P. Russo & M. Gatti in the
ambit of the work for the Geomorphological Map of the
Po Plain, and involved the storage and processing of the
data obtained during various levelling campaigns in an AItimetric
Information System. The available data mainly
concern the eastern part of the plain, which is also that
which is most affected by both natural and artificial subsidence.
Among the results of this analysis, the map shows
the graphics of the vertical movements recorded for each
levelling line and an insert at a scale of 1:500,000 in which
the velocity of the movement recorded with the most" recent
measurements is compared with the greatest velocities
of the subsidence recorded in the previous periods. ,
Comparing the data for the 1970s with the most recent data,
the phenomenon turns out to be markedly reduced in
the whole of the region of Veneto, in the eastern part of
the province of Ferrara and in the coastal strip in Romagna.
On the other hand there has been an increase at Modena,
around Forli, to the south of Ferrara, between Ferrara
and Ravenna, at Ravenna and, above all, in Bologna and
its province (where it now exceeds 10 ern/year). In general
the greatest subsidence occurs in areas which have been
recently industrialised and can be interpreted as being the
result of excessive drainage of ground water.
A synoptic analysis of the movements recorded in the internal
network allows some general considerations to be
made on the influence of the geology on the vertical movement
of the ground; in particular it highlights a frequent
coincidence between rapid velocities of subsidence, including
artificial subsidence, and greater thicknesses of loose
Quaternary and Pliocene sediments.
PAOLO BONI, LAMBERTO LAURETI, CLAUDIA OTTONE,
, LUISA PELLEGRINI & ROBERTO ROSSETTI
Morphotectonic influences on the drainage pattern in the
Northwestern part of the Apennines (Northern Italy)
Dipartimento di Scienze della Terra, Universita di Pavia,
via Ferrata 1,27100 Pavia, Italy
Discussing on geographical features of the Northwestern
part of the Apennines between Orba and Taro rivers (Boni
& alii) 1996), we showed strong differences between the
two sides of the Genoa meridian. Westward of this line,
the mountain range has a SW-NE orientation and it is narrow
and low (respectively under 10 km and 1,000 m) while
eastward the chain has a NW-SE direction and it is wider
and higher (over 30 km and 2,500, m). In this part, we
founded more interesting situations as: 1) a meridian axis
(Antola axis) quite near the western border likely linked to
the major orogenic movements; 2) some evidences of paleosurfaces
and 3) strong changes in the drainage system,
undoubtedly connected with neotectonic events.
Now, discussing on hydrographic pattern and their evolution,
we considered the relationships between hydrography
and tectonics.
Geographical outlines ofthe considered area
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