Mapping slope instability ground factors in the National Park of Gran Sasso – Monti della Laga (Abruzzo, Central Italy): results and perspectives

Abstract

The National Park of Gran Sasso-Monti della Laga (Abruzzo, Central Italy) is representative of a mountainous Mediterranean environment, with a range of elevation from 800 to 2900 meters above sea level and commonly occurring landslides, particularly in the northern belt of the Park. Two main geological formation groups are predominant in the area: the oldest one (of the Trias to Miocene periods) consists of marine carbonate rock formations, which have been tectonically overthrusted by more recent siliciclastic formations during the last orogenetic phase of the Central Appennines (Upper Miocene - Lower Pliocene); these are formed mainly by sandstone and marlstone of the Miocene age and bear the name Flysch della Laga. The research carried out on a pilot area of the Park was addressed to obtain a small scale mapping of both distribution and intensity of the slope instability factors. This was accomplished by considering the percentage occurrence of some instability factors, as the ratio of friction-angle to layering dip-angle less than 1, and the occurrence of morphological signs of instability as active talus. The resulting map (IFP) which could be interpreted as expression of potential susceptibility to slope instability, was not similar to a previous instability hazard map of the same area made by traditional parametric methodology. Instead the IFP map compared with actual distribution of instability phenomena (landslides, badlands, active scree deposits, etc.) over the same area resulted positively correlated at 0.99 probability level. The proposed method seems to be able for predicting the susceptibility to instability trend not only over whole territory but also in areas assumed after traditional methods to have homogeneously distributed hazard class.