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The coastal zone of the Campi Flegrei volcanic district is prone to a wide spectrum of natural hazards, including earthquakes, tsunamis, flash floods, ground deformation, landslides and coastal erosion. In this research we focus on flash flood phenomena occurred in the Pozzuoli catchment, by analyzing historical documents (e.g. newspapers, archive reports, web site news) and integrating the results with daily rain time series of the rain gauge station of Pozzuoli city. In order to understand the evolution of these phenomena, we analyze the 6 November 2011 event that hit the city of Pozzuoli. The study includes the description of meteorological conditions, rainfall properties, ground effects obtained by a web-based research and results obtained simulating flood propagation by means of FLO-2D code. Preliminary results of our research provide a contribution for the understanding of flash floods and flow processes in the study area as well as relevant information for hazard and risk assessment.

This paper shows the results of the numerical modelling of water flow and ion propagation occurring in a test field of KCl wells installed in a landslide of the southern Italian Apennines. Preliminarily, oedometer and direct shear tests on specimens exposed to KCl were carried out in laboratory; ion diffusion and related time-dependent increase in residual shear strength were modelled by a commercial FEM code. Then, the processes occurring in the test field were analysed. The specific discharge profile q(z) along the well height in steady-state conditions and the transient water level restoring h(t) after a rapid drawdown were observed, monitored and modelled. For an axisymmetric domain, a permeability distribution interpreting both q(z) and h(t) in each borehole was determined. Thus, a 3D model of the entire test field was calibrated in MODFLOW-3D FDM code. The results of the experimental/numerical analysis show that, under natural hydraulic potentials, ion propagation from the wells is governed by water flow along a narrow band surrounding the slip surface, much more permeable than the soil above and beneath. Two years after the beginning of the experimentation, the increase in pore ion concentration is noticeable in the monitoring verticals, 5 m far from the KCl wells.

This paper analyzes the effects of a historical rain series on pore water pressure distribution in the Costa della Gaveta landslide, in the Southern Apennine, Italy. The effects of pore water pressure variations on the safety factor and on the displacement rate of the landslide are also analysed. The aim of the investigation is to reach a deeper understanding of the influence of hydrological parameters on the mechanism of movements of the widespread type of active, very slow landslides in fine-grained soils. Pore water pressures were evaluated by means of the 3D finite difference code MODFLOW, applying as boundary condition the long historical rainfall series of the site. The transient analysis carried out with a daily resolution successfully reproduces the trend of piezometric data. The results show that because of the subsoil low permeability (k = 10−8–10−9 m/s), pore water pressure variations caused by rain are significant only at depths lower than about 10 m. Furthermore, noticeable depth-depending time lag is evaluated between the external hydrological input and responses of internal pore water pressures. Pore water pressure variations on the shallowest areas of the slip surface have the greatest influence on the 3D limit equilibrium safety factor and thus on the landslide movements. As a matter of fact, the safety factor seems to be well correlated to the displacement rates evaluated by inclinometers at various depths, on the slip surface. The results of the 3D model provide pore water pressure distributions which are significantly different, both in value and in time trend, from those obtained by using 2D models.

We present a long-range terrestrial laser scanner application for the geostructural mapping of Coroglio cliff, a tuff rock face exposed along the coastal zone of Campi Flegrei, Napoli. The procedure includes several phases (geomorphological analysis, structural field survey, laser scanner data acquisition and data processing, 3-D model development and analysis, geostructural classification of discontinuity orientation data and 2-D vertical cartographic production). Field data were processed with specific software dedicated to geostructural and geometric analysis. Spatial data were managed with a geographical information system and have been used for the construction of 2-D and 3-D geometric models of the rock cliff surface and geostructural interpretation. The main product of this study is a vertical geostructural map of the Coroglio cliff at 1:500 scale that illustrates the spatial distribution and orientation of the major families of structural discontinuities detected along the exposed surface of the cliff. The cartographic product includes base information useful to identify the main rock failure mechanisms along the cliff and represents a first step for the zonation of areas susceptible to block failures and the planning of monitoring activities.

Inclinometer and piezometer measurements have been carried out since 2005 in a slow active earthflow in a clay shale formation of the Italian Southern Apennines. Previous studies outlined the main geometrical and kinematic features of the landslide and the pore pressure response to rainfall. Displacement rates seem to depend on the hydrological conditions as suggested by their seasonal variations. The availability of long time series of data, in some periods recorded in continuum, allows the use of a data mining approach to evaluate the relations among displacement rates in different points of the landslide, and between displacement rates and rainfall. To define such relations, the evolutionary modelling technique EPRMOGA, based on a genetic algorithm, has been used in this paper. The results give a deeper insight into the landslide behaviour on the one hand and, on the other hand, show the reliability of the technique, also in building up management scenarios. In particular, the results show that the landslide displacement rates in different points of the slip surface, although characterized by different values, are linearly dependent and thus have the same time trend, supporting the hypothesis of a constant soil discharge mechanism of movement. Piezometric data in single points cannot be used, in the considered case, to forecast displacements. The obtained relations allow to quantify the displacement rate variations due to contemporary rainfall. The influence of past rainfall is shown to decrease exponentially with temporal distance. Furthermore, the EPRMOGA simulations seem to confirm that there are no other dominant causes, besides rainfall, responsible of displacement rate variations in time.

Active slow-moving landslides in clayey soils exhibit continuous movements generally controlled both in the accelerating and decelerating phases by the pore-water pressure regime that, in turn, is strictly correlated to the net rainfall regime. The paper stresses the importance of a reliable groundwater model to predict these types of movements. To this aim a procedure is proposed to define the transient groundwater regime in the slope on the basis of recorded rainfall and monitoring data; the model is then used to derive the time-dependent shear strength along the main slip surfaces. The displacements at selected points along the slip surface are computed using a phenomenological (i.e., empirical) relationship between the local factor of safety and the displacement rate at those points. The procedure is employed for the analysis of a well-documented case history: the Porta Cassia landslide (central Italy).

This paper is focused on pore pressure response to rainfall in a clayey, deep seated landslide of the Southern Italian Apennines. The displacements of the studied landslide, measured by several techniques, including fixed-in-place inclinometer probes with continuous acquisition, are very slow and show seasonal rate variations of about an order of magnitude. The relationship between such variations, pore pressure changes and rainfall history was investigated. A finite difference code was used in 2D and 3D conditions, carrying out transient analyses with the historical rainfall of the site as boundary condition. We analyzed how the pore pressure time trend and distribution along the slip surface, whose depth varies significantly in the three dimensions, can influence the safety factor. The comparison between calculated and measured pore pressure time trends reveals that the best agreement and a clearer picture of the global response of the landslide are achieved by using a daily discretization.

A framework is proposed to characterize and forecast the displacement trends of slow-moving landslides, defined as the reactivation stage of phenomena in rocks or fine-grained soils, with movements localized along one or several existing shear surfaces. The framework is developed based on a thorough analysis of the scientific literature and with reference to significant reported case studies for which a consistent dataset of continuous displacement measurements is available. Three distinct trends of movement are defined to characterize the kinematic behavior of the active stages of slow-moving landslides in a velocity-time plot: a linear trend-type I, which is appropriate for stationary phenomena; a convex shaped trend-type II, which is associated with rapid increases in pore water pressure due to rainfall, followed by a slow decrease in the groundwater level with time; and a concave shaped trend-type III, which denotes a non-stationary process related to the presence of new boundary conditions such as those associated with the development of a newly formed local slip surface that connects with the main existing slip surface. Within the proposed framework, a model is developed to forecast future displacements for active stages of trend-type II based on displacement measurements at the beginning of the stage. The proposed model is validated by application to two case studies.