ABSTRACT
In 1996 and 1997 a monitoring network was set up at the translational slide of Vallcebre. Fourteen boreholes were equipped with piezometers, wire extensometers and inclinometers. Since then groundwater levels changes and wire displacements have been automatically recorded every 20 minutes. Superficial displacements have been periodically measured with differential GPS. The monitoring network has allowed the observation of sudden changes in groundwater levels and landslide displacements taking place in only a few hours. The immediate response of the groundwater levels to the rainfall has evidenced the role of fissures in the infiltration of the water. A correlation has been obtained between horizontal displacements measured with both inclinometer and GPS and the displacements observed with the extensometer wire. This correlation has provided a continuous record of the rate of the horizontal landslide displacement. The latter tend to be constant for steady positions of the water table suggesting the existence of some viscous component in the landslide mechanism.
