ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

was above average and caused very high water levels in the
investigated basins. The amount of sedimentation could be
measured. In contrast in 1996, after very low winter precipitation
no sedimentation occurred. The water level rises
only little after rain showers in summer because of the very
high infiltration rate but it may be possible that in the case
of a coincidence of snow melt and rain the flood increases.
The corings up to a depth of more then twelve meter show
periods with more organic layers and other periods with
mineral sediments predominating. But there are also periods
with a quick change of conditions. The basis of the
corings has not been dated by 14C or OSI. up to now so
that we have to estimate the time of the beginning of sedimentation.
The oldest absolute date C 4 C) is on an organic
layer at a depth of about 9 meters with an age of 5,750
± 400 BP. The existence Pinus cembra remains points to
the fact that at this time the timberline lay at this altitude
or higher. An estimated age for the beginning of sedimentation
in the basin based on extrapolation of the sedimentation
rate above gives a result of 6,500-7,000 BP. This
agrees with an age given by Heuberger for the end moraine
near the border of the basin. It is possible that under
the coarse sediments there are other layers which cannot
be recovered with the used equipment.
About 4,500 BP one of the basins was damned by debris
flow activity on the talus cone. So a temporary lake was
formed, which has left evidence in the form of fine stratified
sediments with low organic content. The sedimentation
rate was high. After the Atlantic stage climatic changes
may have caused more periglacial morphodynamics in
the catchment area of the basins.
In the Little Ice Age the sediments were markedly coarser
than during the preceding centuries, although the streams
had no direct connection to the glaciers but perlocated in
the debris of the gletscberuorfeld areas. This could indicate
that the fluvial sedimentation into the basins was not only
due to the glacial streams but also to the surrounding
slopes.
All in all the sediments suggest a relationship between climatic
changes which are reflected in fluctuations of the
timberline, and changes in sedimentation dynamics. While
the area has been used as pasture for the last 2,000-3,000
years, no evidence has been found for a possible human
impact on fluvial dynamics so far.
HEINRICH R. BECKEDAHL & MAGANDARAN MOODLEY
Road induced accelerated soil erosion forms:
their classification and potential significance
Department of Geography, University of Natal,
private bag X01, Scottsville, 3209 Pietermaritzburg, South Africa
Roads and the associated embankments result in local modifications
of the surface roughness and infiltration charac-
74
teristics of the immediate area. This is particularly relevant,
but not exclusive to, unarmoured roads. The road surface
proper is compacted and cambered, enhancing these effects.
Consequently, runoff is concentrated as potentially
erosive, confined flow. The injudicious siting of cut embankments,
road culverts and the poor maintenance of
road gutters frequently result in accelerated soil erosion
forms. These range from collapsed embankments to gullied
road verges, to piped and gullied hillslopes.
The present work argues in favour of a fourfold morphogenetic
classification of these accelerated erosion forms.
Through the discussion of selected case studies, it is shown
that these forms develop at rates varying from 4.3 t/a to 65
t/ a. The question of reclaiming erosion damage versus initial
preventative measures is explored using cost-benefit
analysis.
The research suggests that much of the off site damage
could have been avoided with a significant cost saving, had
local geomorphic processes received due consideration at
the time of construction.
FILIPPO BELISARIO3, MAURIZIO DEL MONTE 1,
PAOLA FREDI 1, RENATO FUNICIELL0 2 ,
ELVIDIO LUPIA PALMIERI 1 & FRANCESCO SALVINI 2
Azimuthal analysis of stream orientations
to define regional tectonic lines
1 Dipartimento di Scienze della Terra, Universita La Sapienza,
p.le Aldo Moro 5,00185 Roma, Italy
2 Dipartimento di Scienze Geologiche, Universita Roma Tre,
via Ostiense 169, 00154 Roma, Italy
3localita Colle Ombroso, Porano 05010 Terni, Italy
In the last decade many researchers have focused their attention
on the definition of the role played by tectonics,
and particularly neotectonics, in the geomorphological
evolution of areas located in different parts of the world.
Many attempts have been carried out also in Italy with the
aim of gaining more knowledge about the relationships
between morphology and tectonics. In particular, the examination
of the tectonic control on drainage network geometry
has led to the formulation and improvement of
quantitative methods for studying the azimuthal distribution
of stream channels, which can help efficaciously the
analysis of the field morphological evidence for tectonics
in the definition of the structural arrangement and history
of a given area. The researches so far performed have
shown that tectonics control the drainage network patterns
in a way which differs with varying stream order;
that is, stream channels of lower orders, which are likely
to have joined the net in a later stage of its development,
have resulted to be controlled mainly by tectonic lines active
in very recent times. Moreover the hypothesis has