ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

ley. We hypothesize that this ice lobe eroded a wider and
deeper valley than had existed under a purely fluvial regime,
then filled the valley with recessional outwash as it
retreated.
The variety of glacial landforms and phenomena in the
North Fork Calawah Watershed have had both positive
and negative impacts on the productivity of salmonid fish.
The quantity of coho salmon and steelhead summer rearing
habitat, very important to the productivity of these
species, is unusually low in this watershed, limited by the
drying reach. However, subsurface water flow through the
drying reach provides cool water downstream, lowering
thermal stresses on young fish rearing below the drying
reach. The lower mainstem is protected from the direct delivery
of debris flows from adjacent hillslopes by tbe wide
outwash terraces which provide adequate run-out distances
.. for complete deposition. Furthermore, evaluation of
historic aerial photos suggests that the drying reach buffers
sediment pulses derived from landslide events in the
headwaters of the watershed. Sediment pulses from stormtriggered
debris flows cause large channel disturbances,
such as braiding of the channel, in the drying reach. These
pulses do not continue down the mainstem channel, perhaps
because winter flows in the drying reach are insufficient
to propagate the pulses. It appears that sediment is metered
into the lower mainstem.The protection from direct
delivery of debris flows and the attenuation of sediment
waves as they pass through the drying reach provide for a
more stable channel, and, thus, more stable salmonid habitat
below the drying reach.
TATIANA V. DIKAREVA
Transformation of fluvial relief as the result of irrigation
(valleys and ancient deltas of the Rivers Murgab
and Tedgen in the Central Asia)
Water Problems Institute, Russian Academy of Sciences,
10, Novaya Basmannaya, 107078 Moscou, Russia
Oases of the Central Asia are the hotbeds of civilization.
Irrigational activity in the Tedgen and Murgab oases began
from the IVth millennium BC and goes on till our days.
That's why the relief of valleys and ancient deltas of these
rivers is significantly transformed. One can observe traces
of ancient irrigational buildings together with modern canals,
bars, dams and embankments.
In the relief of Murgab oasis there are a lot of ramparts, irrigational
canals and collectors. All them are of anthropogenic
origin. Some of them, for example, canals Sultan­
Yab, Khurmuz-Fary, collectors Dgar and Kese-Yab are
cleared and straightened branches of Murgab. These branches
had natural levees which became higher thanks to reconstruction
of river bed. These levees are several kilome-
148
ters long and 0,5-30 meters wide at the tops. At the bottom
their width is 300-500 m. Between these levees there
are shallow depressions with gentle slopes (0,003-0,001)
and flat bottoms. Dimensions of these depressions may
reach 103 km', In spring the salinized lakes are in these
depressions.
Initial alluvial-deltaic relief is only on the north-western
edge of the Murgab delta. Here one can see low (up to 1
m) flat ramparts and shallow interstream depressions, opened
to the north. Irrigational relief is clearly expressed in
central and southern regions, where ramparts have maximum
heights and interstream depressions are closed.
Along Murgab there are ravines. Young ravines have
depth of 3-4 m and vertical slopes. Width of their bottoms
in the mouth is sometimes 40-50 m. In the belt 150-200 m
wide along the floodplain of Murgab there are suffosion
craters 1-1,5 ill in diameter.
The Tedgen delta has typical deltaic relief-fan-shaped
branches (most of them are transformed into canals), naturallevees,
composed by light material. Many branches are
filled up, but they are well seen on the cosmic photos. Sometimes
one can meet lake depressions, filled with clay sediments.
Today they are solonchaks. At the borders of the
modern delta there are a lot of barkhans and aeolian sand
hills. There are a lot of anthropogenic relief forms in the
Tedgen delta-natural levees, «depes» and others.
Today the new agroirrigational relief is being formed on
the ancient delta.
RICHARD DIKAU & LOTHAR SCHROTT
The temporal stability and activity of landslides
in Europe with respect to climatic change (Teslec)
Department of Geography, University of Bonn,
Meckenheimer Allee 166, 53115 Bonn, Germany
«The Temporal Stability and Activity of Landslides in Europe
with Respect to Climatic Change (Teslec)» was a research
project supported by the European Commission
which investigated from 1994 - 1996 the interrelationship
between landslides, climate and time.
The project started working as a cooperation network of
scientific institutions from six member states of the European
Community (Germany, France, Italy, Spain, the
Netherlands, United Kingdom). In the talk the project
conception and the main project tasks and objectives will
be presented. The project was based upon the fact, that
available information on existing or relict landslides does
not normally give either the quantitative characteristics or
the physical background of the previous temporal patterns
of behaviour. It is, therefore, difficult to indicate in a reliable
way future patterns of actvities as a function of the past.
Therefore, a more detailed diagnoses of activity requires