Progress in methods in the studies on slope instability in north-western Tuscany (Italy)

The paper summarizes the course of the research on slope instability in the Serchio and Magra River valleys (north-western Tuscany, Italy). Research began during the '80s in the province of Pistoia, where slope instability was directly related to the characteristics of geological units. The maps produced had a particular legend explaining both geological and stability characteristics. The territory was subdivided into instability classes, substantially depending on lithological characteristics and types of landslides. Subsequently, similar maps were drawn to evaluate the landslide hazard connected with earthquakes in a sample area of Garfagnana (mid-upper Serchio valley). More recently, slope stability maps of the most significant portions of Garfagnana and Lunigiana (Magra valley) were published. These maps were subdivided into instability classes related to geological and geomorphological characteristics of the investigated area; geological units were divided into some classes, based on the areal density of landslides. At present, the research on slope instability is particularly aimed at determination of landslide hazard and of the recurrence time of landslides, in relation to the occurrence of triggering factors