Field monitoring in sample sites: hydrological response of slopes with reference to widespread landslide events

The field monitoring is an essential tool to define geotechnical model able to assess landslide stability conditions, with particular reference to the hydrological response of the slopes in presence of widespread landslide events -- the occurrence of several landslides trough wide areas. The results relative to two sample sites, representative of study areas characterised by homogeneous geological elements and where field monitoring has been carried out for adequate time intervals, are illustrated in the paper. In particular, we consider an area with outcroppings formed by a sort of "melange structure" made up of blocks and fragments of phyllites, clays, shales, ect., in a prevalently clayey matrix (Lungro sample site), and an area where are present rocks and soils deriving from weathering of crystalline rocks ("Serra di Buda", Acri, sample site). In the Lungro sample site a piezometer monitoring network and a rain gauge give indications about the hydrological response of the slopes in an urban area; in the "Serra di Buda" sample site the piezometer levels measured for a long time period, and the rainfall, permit to identify some relationships between the cumulative rainfall and the piezometric levels. Values of cumulative rainfall of about 700 mm on 120 days represent a necessary, but not sufficient, condition for critical stability conditions in the considered sample sites, in relation to possible scenarios of widespread landslide events.