THE CONTRIBUTE OF GEOMATICS FOR MONITORING THE GREAT LANDSLIDE OF MAIERATO, ITALY
In the framework of the activities aimed to acquire knowledge and to monitor landslides, an important role is played by geomatics. Topographic surveying is generally used to describe the external surface, to measure the displacements of selected points and to evaluate morphological evolutions. Monitoring is generally extended to the structures located near the crown and the ridges of the landslide. In case of great landslides, a large number of activities (geological, geotechnical, etc...) is performed, and the need to coordinate all of the studies is felt. Presently, the topographic monitoring of some great landslides is in progress in Calabria, performed by the Geomatics Lab of the University of Calabria, Civil Engineering Dept.
The paper deals with the support given by geomatics for monitoring operations of a large landslide, filmed in real time. It affects an entire hill at the edge of the city of Maierato, southern Italy, whose main access road has been bisected. To understand the event, the geophysical and geotechnical methods of investigation have been integrated with geomatic methods.
The geophysical and geotechnical measurements in the area were performed by using inclinometers, seismic testing and tomography; some piezometers have been also installed. The geomatic methods used are: GNSS surveys, laser scanner, digital photogrammetry, total station (continuously operating). GNSS receivers were used in static mode for the reference points. Kinematic and RTK surveys have been performed to obtain the cross sections, useful to correctly interpret the tomography. Laser scanner has been used to obtain a 3D model of the area and to evaluate the volume of the landslide. The total station controls and transmits continuously the position of 20 points.
The design of the control network and the data acquired during the first periodare discussed, with a peculiar attention to the influence of the atmospheric parameters. The first months of monitoring show, on the one hand, an excellent repeatability of the measures, on the other, they confirm what has been obtained with other punctual techniques (inclinometers, etc...) and areal surveys. The integration of the investigations and their results will allow the development of a model of the landslide, also useful for the early warning.