ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

therefore result very useful tools in both general geomorphological
and engineering-morphological studies. So-
.me examples can be found in literature with regard to the
geomorphological problems, like at regional scale'in Hall
(1986), and with regard to the engineering problems, like
at a detailed scale in Knill & Jones (1965) and in Anonimous
(1981).
A such approach has been made in a research about the
gneiss of the Sila Massif (Calabria, Sothern Italy), where
the crystalline rock mass is deeply weathered (Guzzetta,
1974). The study has allowed to fit the data concerning the
different landslide typologies and the landsliding evolution
into the pregnant context of the morphological evolution
of the slopes, also in relation to climate and tectonics. Six
weathering classes have been adopted for the studied
gneiss: fresh gneiss (class I), slightly weathered gneiss (class
II), moderately weathered gneiss (class III), highly weathered
gneiss (class IV), completely weathered gneiss or saprolite
(class V), and residual and colluvial gneissic soils
(class VI) (Cascini & alii, 1992).
The importance of a comprehensive outlook of the
weathering processes patterns, also in order to have a correct
territorial plannning and natural resources management,
needs a cartographical representation of the weathering
profile. This requirement suggested us to define a
methodology for the survey and the mapping of the gneiss
weathering grade, which applies to various scale and also
to different types of crystalline rocks. It consists of a detailed
survey on the field, which is based on a careful analysis
of the outcropping rocks and soils through observations
about consistency, discolouration and texture of the regolith
and through the Schmidt Hammer test results on the
weathered rock. The gneiss weathering grade has been
estimated both at the rock specimen scale both at the rock
mass scale. The weathering grade survey on cutslopes
(Gulla & Matano, 1994) and the analysis of borehole cuttings
has resulted useful in order to have data about the
thickness and the features of the weathering horizons of
the profile.
Some weathering grade maps at various scale have been
compiled with reference to a study area located along the
western slope of the Sila Massif. After a preliminary study
about the weathering conditions along the slope and on
the plateau of the massif, detailed weathering surveys of
some sectors of the slope have been performed and various
weathering maps with a scale among 1:5,000 and 1,200 have
been produced. The scale 1:5,000 has been utilized for
basic geomorphological studies about minor slopes and
drainage basins or for landsliding studies with reference to
a municipal territory. The scales among 1:2,000 and
1:1,000 have resulted useful for the morphological analysis
of particular sectors of the slopes, for the study of the
landsliding phenomena involving inhabited areas and for
the arrangment of engineering-geological and geomorphological
problems, such as those related to the planning of
works and structures. The most detailed scale among
1:1,000 and 1,200 have been used for the study of single
landslide phenomena.
JULIE 1. DIEU l & C. RHETT JACKSON 2
The North Fork Calawah watershed:
dynamics of geomorphically complex landforms
and salmonid fish production
1Rayonier, p.o. box 200, Hoquiam WA 98550, USA
2 Pentee Environmental Inc., 120 Third Avenue Suite 110,
Edmonds WA 98020, USA
Although it drains a basin in one of the world's wettest climates,
receiving about 280 em of precipitation in a average
year, seven miles of the North Fork Calawah River go subsurface
every summer, and long reaches may go subsurface
even in the wet winter season. This hydrologic regime has
important ramifications for salmonid populations and can
only be understood in light of the wathershed's glacial history.
A formal process of environmental evaluation, called
Wathershed Analysis, has led to better understanding of
the complex landforrns and processes that have created
this unique watershed.
The North Fork Calawah River drains 30.000 acres of the
Olympic Peninsula, North America, and lies on the boundary
between the stable northern edge of the peninsula
and the Olympic Mountains. The Calawah Fault trends
west southwest across the northern third ol the watershed;
it has accomodated much of the uplift of the core of the
Olympic Mountains. North of the fault are peripheral
rocks of the Needles-Gray Wolf lithic assemblage and
south of the fault are core rocks of the Western Olympic
lithic assemblage (Tabor & Cady, 1978). Both assemblages
contain poorly-indurated Tertiary lithic sandstone and siltstone
derived from island are volcanics. High uplift rates
ot the Olympic Mountains have led to oversteepened topography,
and this, coupled with the soft bedrock has resulted
in hillslopes shaped by mass wasting events, principally
debris flows. The northern edge and northwest corner of
the Olympic Peninsula have been overridden by continental
glacial lobes that have advanced across the Strait of
Juan de Fuca. During the last glacial advance, ice breached
the northern boundary of the North Fork Calawah watershed
at three low divides. The mainstem of the North Fork
Calawah received large volumes of melt water and outwash,
partially filling the entire length of the valley. The river
has reclaimed much of its pre-glacial floodplain, but remnant
terraces of outwash still remain.
Several river miles of the mainstem go subsurface during
the dry summer months, and certain segments go subsurface
berween storms during the wet winters. Standpipes as
deep as 40 feet have been driven into the channel and have
gone dry during the summer (Larsen, 1987). Hydrologic
calculations and geomorphic interpretations of hillslope
profiles indicate that the drying reach must contain at least
150 feet of porous gravel and sand deposits. The presence
of faceted spurs and small remnants of lateral moraines
along the mainstem valley walls suggests that during some
previous glacial episode an ice lobe in the eastern divide
extended a considerable distance down the mainstem val-
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