Innovative integrated airborne and wireless systems for landslide monitoring

Landslides are a widespread phenomenon over the Italian territory and economical losses due to this hazard are impressive (an average of 2 billion of euros per year in the last 50 years). In the framework of the WISELAND research project (Integrated Airborne and Wireless Sensor Network systems for Landslide Monitoring) funded by the Italian Government, we are testing new monitoring devices devoted to control large landslides at different degrees of activity. Integrated monitoring tools with a strong innovative character are being explored, in particular ground-based wireless sensor networks combined with airborne laser-scanning and hyperspectral surveys.A wireless sensor network (WSN) consists of a set of low cost micro-computers capable to measure physical parameters and to communicate between them. Such a technique allows landslides remote monitoring, measuring spatially distributed parameters and recognizing deformation patterns. Ground-based sensor networks can be effectively integrated with grid-based data measured by the use of airborne techniques. The Light Detection and Ranging (Lidar) technology is used primarily to densely map wide areas, even in presence of a thick vegetation coverage, to retrieve high resolution Digital Terrain Models (DTMs); DTMs are fundamental in monitoring and describing landslide movements. Hyperspectral sensors are capable to measure parameters such as soil moisture content, vegetation coverage and surface roughness, that can be correlated with slope movements.In the first year of the project we tested and validated these monitoring tools on two large earthflows, which are representative of the widespread slope instability in the Northern Apennine: the Silla landslide (Bologna Province, Italy) and the Valoria landslide (Modena Province, Italy). Although characterised by different geological settings and evolution stages, both landslides are associated to a high degree of risk because of the presence of vulnerable elements and their tendency to periodic and abrupt reactivations.Periodic airborne surveys were performed in Valoria site in different periods, in order to monitor the surface displacement of the slopes. Multitemporal Lidar DTMs allowed the calculation of a differential surface, therefore highlighting absolute height variations and recognizing the main landslide components. Hyperspectral data helped in the landslide characterization; for instance the analysis of PCA components are also correlated with results coming from DTM analysis and this has been evidenced to be a proper system to identify depletion and accumulation zones.A prototype wireless sensor network was installed at Silla landslide in July 2009. The network consists of four nodes (located in the upper part of the landslide) configured with static routing table which forward packets (one data every 15 minutes) to a master node connected to a laptop. Parallel to this test, a new node hardware platform, more shaped for low power – high range data transmission in outdoor conditions has been developed and it is now ready to be deployed in the field.