New evolutionary scenarios on the Tessina landslide (North-Eastern Alps) and possible mitigation measures.

The Tessina landslide, first triggered in October 1960, is a complex movement featured by an upper source area of rotational slides turning into a mud flow, that moves through a steep channel lapping the village of Funes and stretching into the Tessina valley down to the village of Lamosano. In the 60s, several reactivations involving about 5 million m3 occurred, causing the filling for a thickness of 30–50 m of the Tessina valley. These movements seriously endangered the village of Funes, which is situated on a steep ridge facing the valley. At that time, Funes was hanging relatively high above the valley, but now it is at nearly the same level as the mud surface. In spring 1992, two large rotational slides occurred after a very long rainy period, causing the collapse of a 70.000 m2 wide area, with a volume bigger than 1 million m3. The dismembered material from this area was channelled along the valley where, due to the continuous remoulding and increase of water content, it formed a large hazardous mud flow, inducing the local Authority to evacuate temporarily the inhabitants of Funes and Lamosano. In 1994, a long tunnel was excavated in the calcareous mass behind the slope, to possibly reduce the water infiltration from the fractured rock into the sliding area. After 1992, some other minor collapses leaded to the formation of smaller mudflows, characterized by an occurrence interval of about 3 years and a hazard level never exceeding that reached in 1992. Recently, the displacement rates monitored in a left hand-side area hanging above the valley, considered stable up to some years ago, suggested a possible future big collapse, thus raising up the risk level. The paper presents the results of the studies carried out in order to understand the stability condition currently existing in this area and the interrelationship among the most significant factors affecting its possible collapse. Moreover, it exams some measures that may be applied in order to improve the overall stability and reduce the risk in the valley.