Meteoric infiltration influence on large mountainous rock slopes stability is investigated by comparing hydrogeologic and gravitational structures from detailed mapping of the 'La Clapière' slope. The slope infiltrated waters are trapped in a perched aquifer that is contained in deposits inside tensile cracks of the upper part of the slope. Flow rates of 0.4 to 0.8 l s−1 from the perched aquifer to the landslide cause landslide accelerations. Numerical modeling shows that a 0.75 l s−1 infiltration yield increases conditions for toppling with failure through tilting of large rock volumes from the perched aquifer bottom down to the foot of the slope.