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La possibilità di determinare dove possono avere origine, nei suoli piroclastici di copertura di versanti acclivi, le frane di scivolamento-colata che così spesso hanno conseguenze catastrofiche in Campania rappresenta un tema con potenziali importanti risvolti applicativi. Ciò perché, in mancanza di un quadro di riferimento concretamente utilizzabile per tale determinazione, non è stato finora possibile perseguire strategie di riduzione del rischio conseguente a tali frane che comportino anche, attraverso opere di difesa attiva, una riduzione della probabilità d’innesco delle frane stesse. Nel presente lavoro si illustra un possibile metodo di individuazione delle aree di versante maggiormente suscettibili allo scivolamento dei suoli piroclastici. Il metodo si basa sulla separazione delle coperture interessate da discontinuità dalle coperture continue e sulla conseguente applicazione di diversi valori di pendenza “soglia” in caso di sequenze di pioggia critiche. Il metodo (denominato “SL.I.DE. (rev. 0)”, da Slide Initiation areas DEtection) trae spunto dall’osservazione di alcune caratteristiche delle frane del maggio 1998 sul Pizzo d’Alvano. Esso è stato quindi applicato alle coperture (pre maggio 1998) dello stesso Pizzo d’Alvano, per sperimentarne le possibilità. I risultati sono stati piuttosto soddisfacenti, tenendo conto che è stato per ora necessario adottare alcune ipotesi esemplificative, relativamente alle quali ulteriori conoscenze e dati potranno permettere l’implementazione nel metodo stesso anche di altri fattori spaziali.

The present paper illustrates the results of an integrated study of a large landslide located on the southern slope of Mount la Civita (Molise, Southern Apennine), an E-W elongated, SSE dipping and 890-m-high monocline carbonate ridge. The upper part of the slope affected by the landslide is largely controlled by strata attitude while its basal part is marked by a strike-slip fault causing the tectonic juxtaposition of the carbonate successions against predominantly clayey flysch units. An integrated study, including geological, geomorphological and geotechnical investigations, was carried out to determine the features of the landslide and to plan further investigation and monitoring. In particular, from 2002 to 2004, Differential Global Positioning System monitoring and core drillings, coupled with inclinometer measurements, were carried out to determine the landslide's kinematics, extent, depth to the surface of rupture and rates of movement. Inclinometer data revealed the presence of the rupture surface at a depth of about 20 m. DGPS monitoring allowed rates of movement up to several tens of centimetres per year to be recorded. The nearby village of Civitanova del Sannio can still be considered at risk due to the landslide, as recent remedial works, consisting mainly of very shallow re-shaping of the slope by blasting and partial filling of trenches, did not succeed in stopping its movement. © 2012 Springer-Verlag.

A significant part of Campania is extensively covered by volcaniclastic soils, deriving from the alteration of airfall-sedimented formations of layered ashes and pumices that were ejected by Campi Flegrei and Mt. Somma–Vesuvius during explosive eruptions. Where such soils cover steep slopes cut in carbonate bedrock, landforms depend essentially on the morpho-evolution of such slopes prior to the deposition of the volcaniclastic soils, because these are generally present only as thin veneers, up to a few meters of total thickness. Historical records and local literature testify that, in this part of Campania, landslides that originate on carbonate slopes covered by such soils and terminate at their foot or at gully outlets are frequent, following critical rainfall events. Such landslides can be classified as complex, occurring initially as debris slides, but rapidly evolving into debris avalanches and/or debris flows. The localization of the initial sliding areas (i.e. ‘‘sources’’) on the slopes depends on both the spatial distribution of characters of the soil cover and the spatial distribution of the triggering rainfall events. It therefore appears reasonable to separate the two aspects of the problem and focus on the former one, in order to attempt an assessment of soil sliding susceptibility in the event of landslide-triggering rainfall. In this paper, some results of the application of a method aimed at such an assessment are presented. The method, called SLIDE (from SLiding Initiation areas DEtection), is based on the concept that, for a spatially homogeneous soil cover and a spatially homogeneous landslide-triggering rainfall sequence, different values of threshold slope gradient for limit equilibrium conditions exist, depending on morphological characters of the soil cover, such as its continuity and planform curvature. The method is based on the assessment of (1) soil cover presence, (2) discontinuities within soil cover, (3) slope gradients and curvature, by means of good resolution DEMs. It has been applied to sample carbonate slopes of Campania, where landslides originated either repeatedly or recently. Results are encouraging, and a soil sliding susceptibility map of a large area, based on a simplified version of method, is also presented.

A complex landslide, which mobilized a calcareous rock mass of about 60,000 m3, occurred on January 3, 2002, along the southwestern slope of Mt. Catiello, above Positano (province of Salerno, Italy). According to established classification schemes, such a landslide can be classified as a rock avalanche or as a complex, dry, extremely rapid rock fall—dry, extremely rapid debris flow. Landslides of this type and dimensions are quite rare in the southern Apennines, and even rarer in the Sorrento-Amalfi Peninsula. Therefore this one represents a singular case for assessing both the mechanisms leading to such a type of sudden, often hazardous mass movements, and the residual hazard still existing on Mt. Catiello. Due to the inaccessibility of the near-vertical rock slopes, the characterization of the instability mechanisms of the landslide was based on analyses of terrestrial stereoscopic photographs, taken from lateral and frontal positions with respect to the 2002 depletion zone, and on measurements/validations of structural settings carried out in accessible sectors of the mountain. Currently, the southwestern slope of Mt. Catiello, which corresponds to the depletion zone of the 2002 landslide, cannot be considered more unstable than the adjacent northern slope, where a smaller rock mass tower, with a volume of 20,000 m3 and clear signs of a propagating deformation-fracturing process at the base, was identified. Considering this remaining unstable rock tower as a part of the mass movement, the distribution of activity of the landslide can be considered as widening, and its state of activity as suspended.