Fabio Ietto

Weathering characterization for landslides modeling in granitoid rock masses of the Capo Vaticano promontory (Calabria, Italy)

This work focuses on developing multidisciplinary researches concerning weathering profiles related to landscape evolution of the Capo Vaticano promontory on the Calabria Tyrrhenian side (southern Italy). In this area, the tectonic uplift, occurred at least since Pleistocene, together with the Mediterranean climatic conditions, is the main cause of deep weathering and denudation processes. The latter occurred on the outcropping rocks of the crystalline-metamorphic basement, made up of weathered granitoids, in turn belonging to the Monte Poro granitoid complex (intermediate to felsic plutonic rocks covered by Cenozoic sedimentary successions). Field observations coupled to borehole explorations, geophysical surveys, and minero-petrographical analyses allowed the characterization of the granitoid outcrops typical of the studied area in terms of kind and degree of slope instability. This characterization was based on suitable correlations verified between several factors as weathering degree, elastic properties of rocks, and discontinuity features. Weathering profiles are mainly composed by rock masses varying from completely weathered rock with corestones of highly weathered rock (classes IV–V) to slightly weathered rocks (class II). The weathered rocks are involved in several landslide typologies such as debris flow (frequency 48.5%), translational slide (frequency 33.3%), and minor rock fall and rotational slide (frequency 9%). The achieved data allowed the establishment of a general correlation between weathering degree and type of slope instability. Debris flow-type instabilities are predominant on the steeper slopes, involving very poor rock masses ascribed to the shallowest portions of the weathering class IV. Translational slides are less widespread than the previous ones and often involve a mixture of soil and highly weathered rocks. Rotational slides are more frequently close to the top of the slopes, where the thicknesses of more weathered rocks increase, and involve mainly rock masses belonging to the weathering classes IV and V. Rock falls mostly occur on the vertical escarpments of the road cuts and are controlled by the characteristics of the main discontinuities. The assessment of rock mass rating and slope mass rating, based on the application of the discontinuity data, allowed respectively an evaluation of the quality of rock masses and of the susceptibility of rock slopes to failure. The comparison between the last one and the real stability conditions along the cut slopes shows a good correspondence. Finally, the geological strength index system was also applied for the estimation of rock mass properties. The achieved results give a worthy support for a better understanding of the relationship between the distribution of landslides and the geological features related to different weathering degrees. Therefore, they can provide a reliable tool to evaluate the potential stability conditions of the rock slopes in the studied area and a general reference framework for the study of weathering processes in other regions with similar geological features.

Epoxy Resin for the Slope Consolidation Intervention on the Tropea Sandstone Cliff (Southern Calabria, Italy)

The Tropea cliff (southern Calabria, Italy), affected by fast weathering processes and landslides, has needed various interventions of slope consolidation aimed at reducing hazard conditions. These interventions were performed with low environmental impact techniques in order to preserve the architecture and the landscape of the area. In 1998, a consolidant resin was tested on a limited portion of the Tropea sandstone cliff. The purpose of this test was checking the resin behavior against erosion processes. Previous researches showed a good resistance to erosion with only a slight opacification of the treated sandstone portion. This paper aims at studying the behavior of the consolidant resin after 17xa0years from its application. The research was performed by several laboratory tests. The Fourier transform infrared spectroscopy analysis has indicated that the consolidant product was an epoxy resin. The scanning electron microscopy analysis has shown that the resin has penetrated into the rock up to 2xa0mm. The chemical analysis further testified that the tested surface is characterized by higher content of soluble salts than the non-treated surface. The salt content is mainly related to the infiltration of water enriched in soluble salts, due to the marine aerosol. The soluble salts, crystallizing in the rock pores and between the mica sheets, produce an increase of physical stress that is responsible of the exfoliation processes of the resin. Therefore, the use of epoxy resin on the tested sandstone rocks increases the strength on the outer rock surface, with a consequent good resistance to erosion processes just in a restricted period. Overtime, water infiltration introduces dangerous soluble salts below the treated surface, causing salt crystallization with important exfoliation processes of the treated rock surface.

Landslide phenomena in weathered granitoid rocks of the Fabrizia surroundings (Serre Massif, southern Italy)

This work shows the preliminary data on the weathered granitoids and related landslide phenomena in the area surrounding Fabrizia, Serre Massif (southern Calabria). Fabrizia lies on an old erosion surface composed of basement rocks made up of weathered granitoids, in turn belonging to the Serre Massif granitoid complex, and overlain by thin eluvial-colluvial deposits. The weathered profiles of the granitoid complex have been studied through a visual description, following both qualitative and quantitative criteria. Weathered profiles are mainly composed by rocky masses varying from completely weathered to highly or moderately weathered terms, characterized by Schmidt Hammer values ranging from 0-20 (class V) to 21-43 (class IV-III). The slopes of the Fabrizia surroundings are characterized by widespread mass movements. Typical landslide typologies are rockfalls for the fresher rocks (class III) and translational slides for the more weathered rocks (classes IV and V). The shallow horizons composed both by thin eluvial-colluvial deposits and by more weathered granitoids (class V-VI), may generate dangerous earth flows, debris flow or debris avalanches under intense and extensive rainfalls.

Integrated coastal zone management in Italy: a gap between science and policy

This paper introduces the need, in Italian countries, of a real integration of scientific knowledge into coastal policy. Actually, in Italy, still exists a gap between Science and Policy, interfering the implementation of an Integrated Coastal Zone Management (ICZM) process, while there is no coordination between local, regional and national authorities. This lack of an overall strategy has induced some regions to adopt regional plans for the sustainable development of their coastal areas, to compensate the shortcomings of a national planning. Besides, along Italian coasts, there is a heavy landscape urbanization producing conditions of environmental decay and highlighting the risk of erosions in littoral areas. In this critical context, it is necessary to adopt an effective Integrated Coastal Zone Management policy, to connect ecosystem and environmental approaches with the social and economic development of coastal areas. So, in Italian landscape, it is necessary to integrate the national cultural heritage into coastal management, joining scientific and cultural issues. In this framework, ICZM process could play an important role connecting scientists and policy makers towards an effective integration for the social and economic growth of local people.

Flash flood event (October 2010) in the Zinzolo catchment (Calabria, southern Italy)

This work aims to describe the flash flood event occurred between 18 and 19 October 2010 in the Zinzolo basin. The Zinzolo basin is located on the Tyrrhenian side, along the northern edge of the Capo Vaticano promontory (Calabria, southern Italy), close to the Tropea village. The drainage area is mainly made up of granitoids, often strongly altered and therefore easily erodible. The geomorphic condition of the drainage network shows low hierarchy degree and downward concavity of the hypsometric curve. These features suggest that the Zinzolo basin is in a juvenile stage and subject to significant modifications, favouring abundance of detritic material in the drainage network. Therefore, small-scale basin, steep slopes, steep bed gradient, widespread instability and high solid loads in the drainage basin, are the main causes of a high predisposition to events of flash-flood type in the Zinzolo basin. The rainfall analysis between 18 and 19 October 2010, shows that in these two days has been recorded (in 6 hours) the highest historical rain event for that area. As a result, the abundant water mixed to detritus have overflowed the banks of the stream in the buried part of the river bed, producing significant damage and hydrogeological hazard in the inhabited riverside areas.

Historic stone portals in the ancient centre of Tropea, Italy: inventory and state of conservation

Abstract This article illustrates the results of a multidisciplinary study carried out in the ancient centre of Tropea in Calabria, southern Italy. The study has two main aspects: the inventory of valuable stone portals found on various historic buildings and an evaluation of their state of conservation. In the research 46 prestigious portals were examined, classified and mapped, and brief descriptions made of both stylistic typologies and peculiar characteristics typical to such ancient architectural features. Their state of conservation was evaluated on the basis of semi-quantitative indexes including visual observations and low impact mechanical tests in order to help understand how best to preserve them. The collected data contribute to an increase in the knowledge about the region’s built heritage and its continuing preservation, and provide a good starting point for further in-depth investigations.

A New Coastal Erosion Risk Assessment Indicator: Application to the Calabria Tyrrhenian Littoral (Southern Italy)

Littoral plains are exposed to natural phenomena, such as sea-waves, tides, rainfalls and sea-level rise, but also to human pressure, determining a growing exposure of the natural and man-made environments to hazard conditions. Through this work, a new kind of multiple approach is proposed to evaluate the coastal risk due to erosion processes, which was first tested on the Calabria Tyrrhenian coast. The resulting data show that 35% of the coastal stretches are classified into very high risk category, 30% into high risk, 28% into medium risk and only 7% into low risk. The coastal areas, characterized by high and very high levels of risk, are formed by sandy beaches and are distributed mainly at the northern side of the regional coastline while the southern part, distinguished mainly by rocky outlines, shows lower risk levels. The comparison between the calculated risk values and the real conditions of the damage state shows a good correspondence, testifying the pertinence of the new methodology. The latter is based on indices with data easily available, making the procedure fast and simple to use and applicable mainly in large scale surveys. The achieved good results suggest that the new methodology used to evaluate the coastal risk condition may be also extended to other Mediterranean beaches.

An integrated approach to investigate slope instability affecting infrastructures

This article focuses on an area located at the northern border of the Monte Poro plateau along the Tyrrhenian coast of Calabria (southern Italy). The area is characterized by weathered gneissic rocks involved in widespread landslides. This research employed an integrated approach concerning the relationships between the geological and geomorphological setting and landslides triggered during the construction of a road. The data were obtained by geological, geomorphological, structural, and geomechanical field surveys, coupled with a geomorphological analysis carried out through a combination of aerial photographs, satellite images, and digital elevation models (DEMs). Rock mass classifications of the weathered gneissic materials were applied to evaluate the quality of the rock masses and to define the potential stability conditions of the slopes. Furthermore, a DEMs analysis of pre- and post-road construction was also performed to define a detailed evolution of the instability conditions affecting the studied escarpment. A total of 32 landslides were recognized before the road construction, while 27 landslides were collected after the road construction. Rotations are the most frequent type of mass movements and involved the more weathered rocks or eluvial/colluvial deposits. Complex landslides are less widespread than the previous ones involving different weathering grades. The results showed that the roadworks had a great impact on the geomorphological scenario in terms of landslide trigger in an area already characterized by a high landslide susceptibility. The approach used can provide a reliable tool to evaluate the hazard conditions in other regions with similar geological features.

Weathering processes in volcanic tuff rocks of the "Rupe di Coroglio" (Naples, southern Italy): erosion-rate estimation and weathering forms

The present work shows the preliminary data on the erosion rate estimation and weathering forms on the outcrop of the Neapolitan Yellow Tuff along the Rupe di Coroglio (Naples, southern Italy). This pyroclastic complex shows abundant alveolar and tafoni forms mostly related to salty seawater and salt spray processes that affect the western portion of the Posillipo hill. In this coastal environment, weathering forms such as alveolar, honeycombs or tafoni are very common producing from small to large deep cavities, development of which produces landslide phenomena. This area has been protected by consolidation interventions such as barrings, retaining walls and anchored structures. After 30 years from first interventions of consolidation, has been observed that some cables of the anchored structures protrude from rock escarpment with values between 5 and 12 cm. Based on these values an average erosion rate of 1.6÷4 mm/year was estimated.