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The work presented in this paper focuses on the third group of movements: slides that move on a shearing surface with a relatively light degradation of the mobilized body.
1.1 Reservoir level and landslide risk
Reservoir operation implies two unfavourable effects for the stability of banks and slopes:
a. The submergence of the toe of a potential landslide
b. The rapid drawdown condition
Regarding the first point, considerer in Figure 1 a slope partially submerged. The groundwater profile will be affected by the position of the reservoir water level whether the slope is fed by the stored water or viceversa. Considerer a potential failure surface and the horizontal free water level within the slope indicated in the figure. This particular case results in hydrostatic profiles of pore water
In the design, construction and operation of dams and reservoir sites, instabilities of banks and ancient landslides by reservoir impoundment are one of most important issues to face. Most of dams and reservoirs are located in natural valleys frequently resulting from fluvial or glacial erosion whose banks are potentially unstable. There is a risk that engineering projects activate or reactivate landslides. In addition, it is common to find valleys whose geologic structure is a syncline involving stratification layers parallel or subparallel to the topographic slope. This situation favours the motion of landslides into reservoirs. In these cases, potential sliding planes are generally located in layers, faults or shearing zones that exhibit smaller shear strength than the surrounding strata.