Modelli e metodi per la previsione e la prevenzione del rischio idrogeologico nei piccoli bacini in ambiente mediterraneo. L’esempio del Rio Pardu (Sardegna centro-orientale)

In this work are presented the results of a study aimed at prediction and prevention of geo-environmental risk associated, in particular, to instability of the slopes in the basin of the Rio Pardu (Central-Eastern Sardinia). This basin has been chosen as the sample because during the last century there occurred a series of very intense rainfall events that caused the collapse phenomena of considerable gravity, including, in particular, that of 1951 that led to the abandonment the villages of Gairo and Osini. The process of analysis, processing and synthesis of thematic data collection, conducted in a GIS environment through different elaborations of the arithmetic overlay mapping, has led to perform a map of landslide hazard and hydrogeological phenomena as resulting from the integration of the geo-environmental factors that play a role in susceptibility to disruption of the slopes: geology, permeability, drainage density, land use and vegetation cover, steepness and exposure. The conceptual model adopted, after collecting statistical and historical landslides data occurred within the trade area, cataloged in the IFFI Project (2005), made it possible to calibrate the actual incidence of individual parameters in the above-mentioned occurrence of landslides. The same values were then used to recalibrate the weights properly used as a first approximation, and also to identify areas that are potentially exposed to various hydrogeological hazard levels. The conceptual model developed allows perimeter areas at hydrogeological risk in basins with similar geological and environmental characteristics.