Evolution of water flow paths in the slope
During the glacial period, the hillslope is considered without
failure (fig. 6a). For similar deep-seated deformation
observed in metamorphic rocks in the Alps, long-term evolution
begins after glacier melting. Glacier melting unloads
the slope which consequence is the formation of failure surfaces
[Agliardi et al., 2001] such as hypothesised at the
“Valfurna” or the “Rosone” landslides [Forlati et al., 2001].
The decompression linked to glacier melting enables a decompression
in the upper part of the slope. In some places,
the deformation can be accommodated by toppling, that
opens the tensile cracks and decompresses some zones,
creating trenches (fig. 6b). This stage is similar to the “Sechilienne”
landslide [Vengeon, 1998]. Toppling creates
trenches progressively filled with a granular matrix
(fig. 6c). In the “La Clapière” landslide, the landslide recuts
the trenches (fig. 2b) and toppling evolves towards the landslide
in the border of the decompressed areas. This relation
between landslides and decompressed areas is confirmed
for all the landslides observed in the valley (fig. 1; fig. 2).
The hydrogeological observations in the Upper Tinée Valley
indicate that the evolution of deformation modifies the
groundwater flows (fig. 4). The more the toppling is developped,
the more important is the drained water volume in the
perched aquifer (tabl. I; tabl. II). When the yearly cyclic hydromechanical
effect had damaged sufficiently the material
within the perched aquifer, a landslide may occur that bypasses
the water flow parallel to the slope (fig. 1c) and decreases
the water pressure in the trenches. After failure, the infiltration
periods occurring upper in the landslide can create significant
hydromechanical effects in the moving-mass.
是什么意思？？？
