Landslide triggering factors in the Slizza Valley (NE Italy)

Studying of landslides triggering factors and zonation of their hazards could help effectively in reducing their damages in the territory in which we are living. To realize this research it has been employed a little watershed called Slizza, as test site, located in Friuli Venezia Giulia Region, in the north eastern part of Italy. The studied has been made on the all region, but the only Slizza watershed has been zoned to test the method validity. Metodologically, at first, the landslide triggering factors occur on the area have been studied. Lithology, slope, aspect, land use, lineament factors (faults), precipitation, sismicity were investigated and their priority were decided using AHP (Analytical Hierarchy Process) method. Also the landslide distribution map has beeen used. Maps rapresenting these seven factors were produced using GIS technique. In the AHP method the seven factors have compared one to each other and their weights were calculated.Every triggering factor has also been divided in several classes due to the influence that every factor has on different type of landslides. To decide their classification has been used the percentage of landslides that occur in a determinate class. In this way it has been possible to obtain a quantitative classification of the different parameters that concur to landslides phenomena. With the values obtained using GIS technique, overlying raster maps, the zonation model of potential instability areas, was presented. To validate the model was also used the GIS technique crossing the model with the landslides distribution map. The accuracy of the results was confirmed by calculating the percentage of landslides comprised in zoned classes.