ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

LEANDRO D'ALESSANDRO, LINA DAVOLI,
ELVIDIO LUPIA PALMIERI & ROSSANA RAFFI
Recent evolution of the beaches of Calabria (Italy)
Dipartimenta di Scienze della Terra, Universita La Sapienza,
piazzale AIda Mara 5,00185 Rama, Italy
Calabria is one of the Italian regions with the longest coasts.
The region extends between the Tyrrhenian Sea (West)
and the Ionian Sea (East) and its coastline has a length of
about 700 km. Long term studies on this region gave a
complete and unitary picture of the recent variations which
have occurred in its shoreline in the past century and,
above all, in the past 40 years.
This study, which was expected to define both natural and
anthropic causes of these variations, relied on analysis of
historical records, as well as on geomorphological, pluviometric
and anemological enquiries. Geomorphological surveys
were carried out on the coastline and on its tributary
catchment basins, to identify active morphogenetic processes
and namely those which influence the entity of solid
supply to sea. In the lack of field measurements, information
on solid load supplied to the beach by streams were
obtained indirectly by processing precipitation data collected
all over the region. Failing adequate data on wave-climate,
resort was made to anemological studies to determine
sea-climate conditions of the shore.
Shoreline variations were investigated on the basis of available
maps and aerial photographs, which made it possible
to reconstruct its history starting from 1850. This study
showed that, over time, Tyrrhenian beaches have been the
first to undergo a strong erosional crisis, with the loss of
about 3,300,000 m' from the mid-1950s to the end of the
197Os. In the past decade, this coastline has reached relative
stability: some of its sites have experienced minor replenishment
processes, but its deltaic cusps have continued to
be subject to severe erosion. Ionian beaches have been stable
from 1954 to 1978, except for some deltaic cusps where
marked erosion processes have been recorded; however,
in the past decade a widespread and significant erosion
process has taken place, which has decreased the surface
area of these beaches by about 4,000,000 m',
The different evolution of Tyrrhenian and Ionian beaches
may be ascribed to their different configuration. Tyrrhenian
beaches are thin strips extending at the foot of steep
slopes, whose watershed is shifted towards the Tyrrhenian
Sea, involving considerable dissimmetry between the
Tyrrhenian side and the Ionian one. Consequently, Tyrrhenian
streams are short and their catchment basins are
small. Conversely, wider beaches are found at the foot of
the Ionian side, with gentler and longer slopes, especially
in its northern portion. These beaches are supplied by
streams with large catchment basins, featured by frequent
outcrops of highly erodable lithologies. Furthermore, the
two coastal areas also have differently shaped seabeds:
along the Tyrrhenian Sea, the bottom is steeper and the
abrasion platform is narrower than along the Ionian Sea.
These differences infer that Tyrrhenian coasts are more
vulnerable and thus were the first to undergo erosion.
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The erosional crisis may have been triggered, at least in
part, by climate. Anemological studies have indicated a
sharp increase in wind speed and frequency and the radical
drop in calms from 1954 to 1978. However, the sensitive
equilibrium of beaches may have been disrupted also by
human activities, i.e. flood-control measures in drainage
basins, quarrying from the fluvial beds and directly from
the beaches. After the 1950s, fast and sizeable urban development
works have markedly destroyed the natural configuration
of the beaches and of their backshore.
In the past decade, Tyrrhenian beaches have apparently
reached some equilibrium, without recovering the width
that they had prior to the 1950s. Unquestionably, this precarious
equilibrium is due in part to the protective structures
(started in the 197Os) and in part to suspension or reduction
in mining from beaches and fluvial beds. Ionian
beaches underwent erosion more than 20 years after
Tyrrhenian ones. Their short period of stability may be justified
by the supply of solid load from very large catchment
basins and by limited urban development of coastline.
Nevertheless, the erosion process which had previously involved
Tyrrhenian coasts has also appeared on Ionian ones
in the past decade. This process has occurred concurrently
with a decrease of precipitations, which may have played a
significant role in the evolution of the beaches of Calabria.
LEANDRO D'ALESSANDRO 1, MAURIZIO DEL MONTE 1,
PAOLA FREDI 1, ELVIDIO LUPIA PALMIERI 1
& SILVIA PEPPOLONI 2
Hypsometric analysis in the study
of Italian drainage basin morphoevolution
1 Dipartimenro di Scienze della Terra, Universita «La Sapienza»,
p.le AIda Mara 5,00185 Rama, Italy
2 via del Forte Bravetta, 164, 00164 Rama, Italy
The plano-altimetric configuration of drainage basins is expressible'
as it is known, through the hypsometric curves;
many recent studie have shown that the interpretation of
such curves can differs deeply as a consequence of the
structural setting in which the drainege basins are located.
In details, if in the study area the tectonics has been inactive
since a long time, the hypsometric curves can express
the stage of the «geomorphic cycle» of the basin itself, in
accordance with the classic interpretation by Strahler. On
the contrary, when the drainege basins ar located in areas
where tectonics is recent or still active, this interpretation
is not completely fulfilled. Previous studies demonstrated
that in the case of Italy the plano-altimetric configuration
of drainage basins can be more easily expressed in terms of
typology and spreading of denudational processes, although,
in some cases, the classic interpretation can be considered
still valid.
This study is framed into this research sector and its aim is
to improve the significance of the cause/effect relations
between morphogenetic processes and plano-altimetric