Structural settings and lithological characteristics are traditionally
assumed to influence the development of erosional landforms, such
as gully networks and rock couloirs, in steep mountain rock basins.
The structural control of erosion of two small alpine catchments
of distinctive rock types is evaluated by comparing the correspondences
between the orientations of their gullies and rock couloirs with
(1) the sliding orientations of potential slope failures mechanisms,
and (2) the orientation of the maximum joint frequency, this latter
being considered as the direction exploited primarily by erosion
and mass wasting processes. These characteristic orientations can
be interpreted as structural weaknesses contributing to the initiation
and propagation of erosion. The morphostructural analysis was performed
using digital elevation models and field observations. The catchment
comprised of magmatic intrusive rocks shows a clear structural control,
mostly expressed through potential wedges failure. Such joint configurations
have a particular geometry that encourages the development of gullies
in hard rock, e.g. through enhanced gravitational and hydrological
erosional processes. In the catchment underlain by sedimentary rocks,
penetrative joints that act as structural weaknesses seem to be exploited
by gullies and rock couloirs. However, the lithological setting and
bedding configuration prominently control the development of erosional
landforms, and influence not only the local pattern of geomorphic
features, but the general morphology of the catchment. The orientations
of the maximum joint frequency are clearly associated with the gully
network, suggesting that its development is governed by anisotropy
in rock strength. These two catchments are typical of bedrock-dominated
basins prone to intense processes of debris supply. This study suggests
a quantitative approach for describing the relationship between bedrock
jointing and geomorphic features geometry. Incorporation of bedrock
structure can be relevant when studying processes governing the transfer
of clastic material, for the assessment of sediment yields and in
landforms evolution models.