Eastern Liguria Research Articles

A Study on the Factors Controlling the Kinematics of a Reactivated and Slow-Moving Landslide in the Eastern Liguria Region (NW Italy) through the Integration of Automatic Geotechnical Sensors

This paper deals with the investigation of factors influencing the movement patterns of a reactivated slow-moving landslide situated in the eastern Liguria region (NW Italy) through the analysis of extensive ground-based hydrological and geotechnical monitoring data. Subsurface horizontal displacement and pore water pressure data were acquired simultaneously by means of automatic sensors positioned at pre-existing and localized failure zones. The joint examination of field measurements enabled us to explore the connections between rain, pore water pressure, and displacements. The results of continuous displacement monitoring showed that the landslide kinematics involved phases of extremely slow movements alternated with periods of relative inactivity. Both stages occurred prevalently at seasonal scale displaying similar durations. The slow-motion phases took place at relatively constant pore water pressure and were ascribed to mechanisms of viscous shear displacements along failure surfaces. Inactive phases entailed no significant deformations, mostly corresponding to prolonged dry periods. The two motion patterns were interrupted by episodic sharp deformations triggered by delayed (preparation periods from 4 to 11 days) rainfall-induced pore water pressure peaks, which were ascribed to sliding mechanisms taking place through rigid-plastic frictional behaviour. During these deformation events, hysteresis relationships between pore water pressure and displacement were found, revealing far more complex hydro-mechanical behaviour.

Large-Scale Re-Implantation Efforts for Posidonia oceanica Restoration in the Ligurian Sea: Progress and Challenges

The Ligurian Sea (NW Mediterranean) has been a focal point for numerous interventions aimed at restoring Posidonia oceanica meadows. The success of pioneer restoration actions in France during the 1970s stimulated similar initiatives across the Mediterranean Sea. Early attempts in the Ligurian Sea were implemented in 1993 and 1996 on limited seabed areas (i.e., tens of square meters) at the two coastal sites of Sori and Rapallo (Liguria, NW Italy). No further initiatives have been reported for the Ligurian Sea until 2022. In that year, a large-scale restoration project, which uses biodegradable mats coupled with metal mesh, began in Liguria. Different levels of anthropogenic pressure and wave exposure characterize the three investigated locations: (1) Portofino, on the eastern Liguria and on the border with the Portofino Marine Protected Area; (2) Bergeggi in the central Liguria and within the Isola di Bergeggi Marine Protected Area; and (3) Sanremo in the western Liguria, without any formal protection. Despite recent setbacks caused by severe storms in late 2023, which particularly damaged the Portofino site, ongoing monitoring revealed promising survival rates. Most notably, the site in Bergeggi displayed a 90% survival rate in September 2023. Although challenges to restore P. oceanica beds persist, such as mitigating damages caused by unpredictable events, this extensive re-implantation initiative offers the opportunity to evaluate the effectiveness of new basin-scale restoration strategies. This approach marks an important step in the conservation of Posidonia oceanica habitat.

Historical information sheds new light on the intensification of flooding in the Central Mediterranean

Hydrological disasters, such as floods, can have dire consequences for human societies. Historical information plays a key role in detecting whether particular types of hydrological disasters have increased in frequency and/or magnitude and, if so, they are more likely attributable to natural or human-induced climatic and other environmental changes. The identification of regions with similar flood conditions is essential for the analysis of regional flooding regimes. To this end, we here present the longest existing flood reconstruction for the Eastern Liguria Area (ELA) in northwestern Italy, covering 1582 to 2022 CE, which offers a case study representative of the central Mediterranean region. An Annual Flood Intensification Index was developed to transform the historical data into a continuous annual hydrological time-series contained by a homogeneous data structure for the study-area. We found two change-points (trend breaks) in the reconstructed time-series, in 1787 and 1967, with only occasional heavy floods comparable to present-day disasters occurring before the first change-point, and an increasing intensification of floods after the second change-point up to the present day. The recent intensification of flooding in the ELA, associated with changes in land use and land cover, also appears to coincide with phases in which hydrological hazards have become more changeable and extreme in disaster-affected areas. This is evidenced by river basin responses to human-induced disturbances.

The Portofino Conglomerate (Eastern Liguria, Northern Italy): Provenance, Age and Geodynamic Implications

The Portofino Conglomerate (PC) cropping out in the Eastern Liguria is an approximately 500 m thick, very gently folded succession mainly composed of poorly bedded and mostly matrix-supported conglomerates. It stratigraphically rests on the Helminthoid Flysch (UA3) thrusted onto the Antola Unit. We vertically distinguished three mostly ruditic litho/petrofacies: (i) Paraggi (fP) with carbonate clasts from an Helminthoid Flysch succession; (ii) Monte Pallone (fMP) with prevailing carbonate and meta-carbonate clasts and minor quartz-rich (meta)siliciclastic and high-pressure–low-pressure (HP-LP) metabasite clasts; and (iii) Monte Bocche (fMB) with dominant quartz-rich (meta)siliciclastic, meta-carbonate clasts, and minor granitoid elements and medium-temperature–high-temperature (MT-HT) regional metamorphic rocks. The middle-upper Eocen age of Paraggi litho/petrofacies is constrained by well-preserved microforaminifers (e.g., Globigerinatheka) recovered in the matrix. During its sedimentation, the directions of the paleocurrents would indicate that the PC underwent a counterclockwise rotation coeval with the first Cenozoic rotational phase of the Sardinia–Corsica system (50–30 Ma) and then stopped before the sedimentation of the Monte Pallone and Monte Bocche litho/petrofacies. The vertical compositional variation in the sedimentary inputs suggested that the PC is the result of a progressive deepening of the erosional level of a tectonic pile that can be located in the Ligurian Alps Chain. We considered the PC as the likely apical part of a submarine fan deposited in a piggy-back/thrust-top basin within the Alpine nappe stack. This sedimentary body was later tectonically transported eastward with its UA3 Helminthoid Flysch substrate (similarly to Epiligurian Units of the Northern Apennines) onto the Apenninic orogenic system (i.e., the Antola Unit).

New phreatic and stygobitic hydrobiids from the Northern Apennines in Piedmont, Liguria and Emilia-Romagna (Gastropoda: Caenogastropoda: Hydrobiidae)

Five new species of phreatic and stygobitic hydrobiids are here described for the Ligurian- Piedmontese and Emilian Apennines. Two species belong to the genus Alzoniella: Alzoniella borberensis n. sp., endemic to the sub-basin of the Borbera and Spinti streams, and to the lower stretch of the Scrivia stream, in the province of Alessandria, and Alzoniella isoensis n. sp., limited to the middle course of the Scrivia stream and to the basin of the Polcevera stream, on the Tyrrhenian sector of the Genoa province. Three species belong to the genus Fissuria: Fissuria globosa n. sp., widespread throughout the sub-basin of the Scrivia stream (Genoa and Alessandria provinces), as well as in other Apennine watercourses of the provinces of Alessandria, Piacenza, Parma and Reggio Emilia; Fissuria varicosa n. sp., present in the same area of Alzoniella borberensis n. sp., but also found in the Nure and Arda streams (Piacenza province) and in the Stirone stream (Parma province), and Fissuria sossoi n. sp., limited to the sub-basin of the Stura di Ovada streams (Genoa province). The first species, assigned to the genus Alzoniella Giusti & Bodon 1984 based on its anatomical characters, has a shell with peristome detached from the last whorl, such as that of other phreatic species already known for eastern Liguria and central Italy, but differs from these in the shorter shell. The shape of the shell of A. borberensis n. sp. resembles that of other crenal or stygobitic species, widespread in northern Italy. A. isoensis n. sp., is very similar to A. borberensis, although the peristome is not sinuous superiorly on the outer edge of the shell, but differs sharply in the anatomical characters. The other taxa with valvatoid shells here described, can be ascribed to the genus Fissuria Boeters 1981 based on their anatomical characters, and show some peculiarities of the male genital tract that distinguish them from the other congeneric species so far known for southern Europe. The three new species of Fissuria differ mainly in the characters of the shell, more or less globose in F. globosa n. sp., more conical in F. sossoi n. sp. and more flattened in F. varicosa n. sp.; the latter is also characterized by the presence of a marked varix behind the peristome. Altogether, these new species can be defined as phreatic, as they colonize groundwater near watercourses; only A. isoensis n. sp. has a wider ecology, as it also lives in karst groundwater and groundwater in rocks permeable by fracking.
 [Article in Italian]

Serpentinite and ophicalcite in the architecture of eastern Liguria and as decoration of Tuscan religious buildings

The serpentinite is a metamorphic rock with a particular texture and colour ranging from light to dark green that was used in the Middle Ages architecture of Eastern Liguria and Central Tuscany as an element of embellishment of high value. This value was in relation to its aesthetic aspect but also to the high processing cost due to its hardness, requiring specialized workers. This research aims at broadening the knowledge related to the use of serpentinite together with that of a reddish brecciate variety of this lithotype, an ophicalcite traditionally called “Rosso di Levanto”. Conservation issues of these two materials, which are affected mainly by physical phenomena, will be highlighted.

Rainfall-Induced Shallow Landslide Detachment, Transit and Runout Susceptibility Mapping by Integrating Machine Learning Techniques and GIS-Based Approaches

Rainfall-induced shallow landslides represent a serious threat in hilly and mountain areas around the world. The mountainous landscape of the Cinque Terre (eastern Liguria, Italy) is increasingly popular for both Italian and foreign tourists, most of which visit this outstanding terraced coastal landscape to enjoy a beach holiday and to practice hiking. However, this area is characterized by a high level of landslide hazard due to intense rainfalls that periodically affect its rugged and steep territory. One of the most severe events occurred on 25 October 2011, causing several fatalities and damage for millions of euros. To adequately address the issues related to shallow landslide risk, it is essential to develop landslide susceptibility models as reliable as possible. Regrettably, most of the current land-use and urban planning approaches only consider the susceptibility to landslide detachment, neglecting transit and runout processes. In this study, the adoption of a combined approach allowed to estimate shallow landslide susceptibility to both detachment and potential runout. At first, landslide triggering susceptibility was assessed using Machine Learning techniques and applying the Ensemble approach. Nine predisposing factors were chosen, while a database of about 300 rainfall-induced shallow landslides was used as input. Then, a Geographical Information System (GIS)-based procedure was applied to estimate the potential landslide runout using the “reach angle” method. Information from such analyses was combined to obtain a susceptibility map describing detachment, transit, and runout. The obtained susceptibility map will be helpful for land planning, as well as for decision makers and stakeholders, to predict areas where rainfall-induced shallow landslides are likely to occur in the future and to identify areas where hazard mitigation measures are needed.

Demagistrisite, the Missing Link in a Polysomatic Series from Lawsonite to Orientite

Abstract Demagistrisite, ideally BaCa2Mn3+4(Si3O10)(Si2O7)(OH)4·3H2O, is a new mineral found at the Cerchiara mine (eastern Liguria, La Spezia province, Italy). The ore consists of rhythmic interlaying of braunite-bearing metasediments (5–15 cm thick) and hematite-rich cherts. Demagistrisite occurs in association with cerchiaraite-(Mn), namansilite, noelbensonite, orientite, richterite, ruizite, and saponite in matrix consisting of braunite, calcite, cryptomelane, orthoclase, and quartz. Demagistrisite crystals occur as tightly intergrown blades or as millimeter-sized prisms and needles with square cross-section, typically with irregular terminations, and rarely terminated by a low-angle pyramid. The mineral is orange brown to red brown, streak is beige, and luster is vitreous, translucent to transparent. Fracture is irregular. In thin section, it is orange brown. The mineral is optically biaxial (–) with α 1.805(5), β 1.825(5), γ 1.8305(5) (white light); 2Vmeas 58(5)°, 2Vcalc 54.7°; optical orientation X = c, Y = b, Z = a. Dispersion is very strong, r > v. Pleochroism is strong with X orange yellow, Y red brown, Z red brown; X << Z < Y. It is unreactive in concentrated HCl at room temperature. Thirteen chemical analyses by WDS-EMPA gave the following empirical formula (based on 24 O apfu): (Ba0.69Ca1.25Mn2+0.70Sr0.21Na0.12Mg0.02)Σ2.99(Mn3+3.97Al0.03)Σ4(Si3O10)(Si2O7)(OH)3.87·3.13H2O. The mineral is orthorhombic, space group Amm2, with unit-cell parameters a 16.312(8), b 6.176(4), c 9.075(6) Å, V 914.2(10) Å3, and Z = 2. The seven strongest X-ray powder diffraction lines are [d Å (I%; hkl)]: 16.21 (49; 100), 4.86 (44; 111), 4.34 (56; 102,211), 2.871 (54; 220), 2.731 (100; 511,013), 2.671 (74; 320,113,502), and 2.426 (51; 222,313,611). The crystal structure (R1 = 0.0572 for 1485 reflections with I > 2σI) is based on straight edge-sharing chains of Mn3+-centered octahedra extending along [010], which are bridged by disilicate (Si2O7) and trisilicate (Si3O10) groups, yielding a framework. Cavities within this framework contain two large cation sites. The structure of demagistrisite can be considered transitional between the structures of orientite and noelbensonite. Demagistrisite is named in honor of Leandro de Magistris (1906–1990).

Application of Bioengineering Techniques as Geo-Hydrological Risk Mitigation Measures in a Highly Valuable Cultural Landscape: Experiences from the Cinque Terre National Park (Italy)

In this work, experiences from the use of bioengineering techniques as geo-hydrological risk mitigation measures within the territory of Cinque Terre National Park (Eastern Liguria, Italy) after an extreme rainfall event that occurred on 25 October 2011 are described. This rainstorm was responsible for intense erosive processes and triggered numerous shallow landslides, causing severe structural and economic damage. After this disastrous event, many bioengineering interventions were planned to stabilize the most unstable slopes and the most problematic streams. Based on multidisciplinary studies and field surveys, an inventory of the executed bioengineering works was compiled. Subsequently, on the basis of expert judgement, both the efficiency and effectiveness of the works three years after their construction were examined. Furthermore, the compliance of the executed works with the design requirements was analysed. This study revealed that some of the investigated works lack post-intervention maintenance and require the adoption of remedial measures aimed at improving the biotechnical functions of live materials, which are often ineffective. This case study highlights the importance of technical aspects that should be considered during the design phase of bioengineering works, especially when implemented within protected areas. Specifically, it would be greatly helpful to define instructions for post-intervention maintenance and monitoring and to perform vegetational studies. Considering the great cultural and natural heritage of the study area, the obtained results are expected to provide useful information for the definition of guidelines for the best practices to be adopted when future bioengineering works are planned for geo-hydrological risk management purposes.

Anthropogenic landforms in an urbanized alluvial-coastal plain (Rapallo city, Italy)

ABSTRACT This paper describes the anthropogenic landforms of the alluvial-coastal plain of Rapallo (Eastern Liguria, NW Italy). Since the second half of the nineteenth-century Rapallo experienced a progressive urban sprawl that became particularly intense after the Second World War and severely modified the former landforms. The identification and mapping of morphological changes was performed through a multi-temporal comparison of historical and recent maps and aerial photographs, an analysis of geo-thematic maps and urban planning documents, an interpretation of stratigraphic data from boreholes, and a field survey activity. The main anthropogenic interventions that shaped the urban landscape of Rapallo were riverbed diversions and channelization, excavations, fillings, and embankments construction along the shoreline. These elements highlight the relevant extent of the human imprint on the pristine environment. Furthermore, the identified anthropogenic geomorphological features, combined with the local physiographic and climatic features, increased flood and sea storm hazards and risks.

Isselite, Cu6(SO4)(OH)10(H2O)4⋅H2O, a new mineral species from Eastern Liguria, Italy

AbstractThe new mineral isselite, Cu6(SO4)(OH)10(H2O)4⋅H2O, has been discovered in the Lagoscuro mine, Monte Ramazzo mining complex, Genoa, Eastern Liguria, Italy. It occurs as sprays of blue acicular crystals, up to 0.1 mm long, associated with brochantite and posnjakite. Streak is light blue and the lustre is vitreous. Isselite is brittle, with irregular fracture and good cleavage on {001} and {100}. Measured density is 3.00(2) g/cm3. Isselite is optically biaxial (–), with α = 1.599(2), β = 1.633(2) and γ = 1.647(2) (determined in white light). The measured 2V is 63.6(5)°. Dispersion is moderate, withr>v. The optical orientation isX=b,Y=candZ=a. Isselite is pleochroic, withX= light blue,Y= blue,Z= blue;X<<Z<Y. Electron microprobe analyses give (wt.%): SO311.45(21), MgO 0.31(7), CoO 1.07(14), NiO 9.41(90), CuO 51.29(126), ZnO 1.10(20), H2Ocalc24.21, total 98.84. The empirical formula of isselite, based on Σ(Mg,Co,Ni,Cu,Zn) = 6 atoms per formula unit, is (Cu4.80Ni0.94Co0.11Zn0.10Mg0.06)Σ6.00(S1.06O4.19)(OH)10⋅5H2O. Isselite is orthorhombic, space groupPmn21, with unit-cell parametersa= 6.8070(14),b= 5.8970(12),c= 20.653(4) Å,V= 829.0(3) Å3andZ= 2. The crystal structure of isselite was refined from single-crystal X-ray diffraction data toR1= 0.067 on the basis of 2964 reflections withFo> 4σ(Fo). It shows a layered structure formed by zig-zag {001} layers of Cu-centred polyhedra. Sulfate groups occur in the interlayer along with one H2O group. Isselite is chemically related to redgillite and montetrisaite.

STRATIGRAFIA E SEDIMENTOLOGIA DEI "CALCARI E MARNE A <em>RHAETAVICULA CONTORTA</em> AUCTT. (NORICO-RETICO) DELLA TOSCANA NORD-OCCIDENTALE - NUOVA SUDDIVISIONE FORMAZIONALE

Nine sections from the "Limestones and marls with Rhaetavicula contorta" Auctt. (Norian-Rhaetian) of the Tuscan Nappe in eastern Liguria and northwestern Tuscany, have been examined for their stratigraphic and sedimentological characteristics. The results obtained have been integrated with data pertaining to the previously studied Pania di Corfino section.
 Two formations were identified and studied in detail: that of Pania di Corfino and that of La Spezia.
 Where present, the Pania di Corfino Formation accounts for the lower portion of the sections. It consists mainly of thick beds and massive layers of dolomites, dolomitic limestones and limestones. Thinly-bedded dark limestones appear less frequently, while layers rich in clay are rare. The top of the formation is surely of Rhaetian age, in some sections, as indicated by the presence of Triasina hantkeni Majzon; in the others, it is Norian-Rhaetian. The age of the bottom portion can be regarded as Norian-Rhaetian in all the sections; the presence of considerably thick deposits beneath the established Rhaetian layers in some sections, however, suggests an Early Rhaetian or even Late Norian age.
 The depositional environment of the Pania di Corfino Formation may be envisaged as an epicontinental carbonate platform with predominantly restricted water circulation on which fine carbonate sediments are deposited beneath the wave base; features suggesting a tidal flat are rare. The environment of deposition was, for brief periods only, that of a platform with open circulation in which the effects of wave-motion were prominent; features strictly relatable to a true platform edge have not been found.

Observational and Modelling Study of a Major Downburst Event in Liguria: The 14 October 2016 Case

Downbursts are very disruptive weather events that can produce large amounts of damage. The most studied downbursts are those occurring in the United States and continental Europe, but they can happen globally. This work is an observational and modelling analysis of a major downburst event that occurred on 14 October 2016 over eastern Liguria (Italy). This downburst affected an area 30 km long and 10 km wide, producing observed wind gusts of 40 m/s with major impacts to railways, trees, and houses, with more than 2.5 million euros of damage. First, the general environment influencing this downburst is identified and analyzed, then the event is reproduced with a small multi-physics high-resolution ensemble using the Weather Research and Forecasting (WRF)–advanced research WRF (ARW) model, with 1 km horizontal grid spacing. The event was poorly predicted beforehand, and the difficulty in forecasting this event is confirmed by the fact that so few ensemble members suggested the occurrence of damaging winds over eastern Liguria. However, one of the eight members performed well and its output helped to reveal the primary mechanisms for the downburst, suggesting that high-resolution ensembles using mixed physics may be a useful tool for improving the prediction of similar extreme events in the Mediterranean region in the future.

Fungal richness in the extreme environments of the Libiola mine (eastern Liguria, Italy): correlations among microfungi, lithology, mineralogy, and contaminants

A small sulphide-rich waste-rock dump from the derelict Libiola mine (eastern Liguria, Italy) was studied for evaluating the fungal richness as well as the correlation among microfungi and lithology, mineralogy, and contaminants. The waste-rock dump is characterized by severe environmental conditions in particular for the (1) high metal and sulphur contents, (2) presence of reactive sulphides (mainly pyrite) triggering acid mine drainage processes, (3) acid-to-strong acid pH values, and (4) high cementation grade of the sediments evolving up to hardpans. Despite these critical and dangerous environmental conditions, a total of 603 CFUs belonging to 30 filamentous fungal species were isolated. Correlations analyses underlined that serpentinite-rich samples resulted particularly poor of fungal richness, with respect to sulphide-mineralized basalts. Only some Penicillium species, in fact, resulted adapted to survive in serpentinitic samples. Finally, among the isolated species, Cladosporium cladosporioides, C. iridis, C. tenuissimum, Metarhizium anisopliae, Penicillium brevicompactum, P. expansum, and Phanerochaete sordida appeared particularly well adapted to the extreme edaphic conditions of the Libiola mine. These results allowed the selection of particularly adapted and tolerant fungal strains usable in biotechnological processes for bioremediation.

Investigation on Farmland Abandonment of Terraced Slopes Using Multitemporal Data Sources Comparison and Its Implication on Hydro-Geomorphological Processes

This paper presents a quantitative multi-temporal analysis performed in a GIS environment and based on different spatial information sources. The research is aimed at investigating the land use transformations that occurred in a small coastal terraced basin of Eastern Liguria from the early 1950s to 2011. The degree of abandonment of cultivated terraced slopes together with its influence on the distribution, abundance, and magnitude of rainfall-induced shallow landslides were accurately analysed. The analysis showed that a large portion of terraced area (77.4%) has been abandoned over approximately sixty years. This land use transformation has played a crucial role in influencing the hydro-geomorphological processes triggered by a very intense rainstorm that occurred in 2011. The outcomes of the analysis revealed that terraces abandoned for a short time showed the highest landslide susceptibility and that slope failures affecting cultivated zones were characterized by a lower magnitude than those which occurred on abandoned terraced slopes. Furthermore, this study highlights the usefulness of cadastral data in understanding the impact of rainfall-induced landslides due to both a high spatial and thematic accuracy. The obtained results represent a solid basis for the investigation of erosion and the shallow landslide susceptibility of terraced slopes by means of a simulation of land use change scenarios.

The Ottone-Levanto Line of Eastern Liguria (Italy) uncovered: a Late Eocene-Early Oligocene snapshot of Northern Apennine geodynamics at the Alps/Apennines Junction

The Ottone-Levanto Line of Eastern Liguria (Italy) uncovered: a Late Eocene-Early Oligocene snapshot of Northern Apennine geodynamics at the Alps/Apennines Junction

Assessment of soil erosion risk in a typical Mediterranean environment using a high resolution RUSLE approach (Portofino promontory, NW-Italy)

ABSTRACT Particularly the Liguria region in Northern Italy is highly affected by soil erosion processes. This study was conducted in the Portofino promontory in eastern Liguria, to predict potential annual soil loss using the Revised Universal Soil Loss Equation (RUSLE). Moreover, we evaluate the relative accuracy of the predictions at detailed scale, using high resolution spatial information for model calibration. The RUSLE factors were calculated for the study area based on terrain survey data and rain gauge measurements. The results were plotted on a 1:10,000 scale soil erosion map and subsequently compared with the European soil loss estimation method (RUSLE2015) developed by the European Joined Research Centre. This study shows that the RUSLE2015 model can be applied in a typical Mediterranean environment such as the Portofino promontory. However, the accuracy of the single factors we calculated using high resolution data sets might improve the results substantially and thus, also model efficiency.

Sediment mobility and connectivity in a catchment: A new mapping approach

In fluvial basin analysis, sediment connectivity is an important element for defining channel dynamics. Nevertheless, although several approaches to quantify this concept have been trialed, there is considerable discussion about ways to measure and assess sediment connectivity. The present study investigates sediment connectivity through the definition of a new index, aiming to integrate functional aspects within a structural component. Our objective is to produce a sediment flow connectivity index (SCI) map, directly applicable to monitoring and management activities. Our SCI is defined as the result of the gradient-based flow accumulation of a sediment mobility index, which is in turn a simple function of rainfall, geotechnical properties of soil and land use. This method is here applied to the Vernazza basin (eastern Liguria, Italy), producing a sediment connectivity map that shows good performance in predicting the positions and accumulation paths of mobilized deposits detected on the ground after the October 25th, 2011, flood event. A further evaluation of the proposed index is performed through a comparison of the maps derived using the SCI and connectivity index (IC) developed by Cavalli et al. (2013), which highlights comparable quantitative overall performances, together with a slightly better qualitative identification of subtle sediment flow paths by the SCI. In spite of current limitations due to, e.g., the local nature of the final index, the availability of input information through open global datasets promises the potential application of this method to larger-scale assessments, paying attention to properly addressing upscaling and standardization issues.

A geomorphological and hydrodynamic approach for beach safety and sea bathing risk estimation

Coastal areas represent one of the most important economic driving forces for entire countries. In the last decades, along coastal areas it has been observed a marked increase in risk of bathing due to the advent of mass tourism, particularly during the summer season. Local and global reports on bathing-related incidents highlight the importance of beach safety in coastal management. This paper describes a cost-effective and semi-quantitative approach for beach safety and sea bathing risk estimation. The methodology was applied to a coastal stretch located in eastern Liguria (north western Italy, Ligurian Sea), which is characterized by high tourism vocation and can be considered indicative of some main features of Mediterranean shores. The peculiar geomorphological and hydrodynamic hazard descriptors and the beach accessibility (i.e., the exposure of bathers to hazard) of the study area have been evaluated by means of open source archive information, field surveys and expert judgement. Subsequently, probability theory was used to estimate the Hazard Index and the Risk of Bathing Index. The resulting zoning maps show that beach safety and risk of bathing do not have a uniform distribution along this coastal sector since both hazard and risk conditioning variables can frequently change from one site to another. Considering the large and rapidly expanding tourism activities in coastal environments, the obtained zoning maps reveal that the proposed method can be a flexible and simple tool for stakeholders in charge of coastal management. The proposed approach may be also adapted to other coastal-type environments by means of an accurate identification of hazard and beach accessibility descriptors that better characterise the stretch of coast under consideration.

Heavy Rainfall Triggering Shallow Landslides: A Susceptibility Assessment by a GIS-Approach in a Ligurian Apennine Catchment (Italy)

In recent decades, the Entella River basin (eastern Liguria) has been affected by several rainfall events that induced widespread shallow landslides and earth flows on the slopes; roads, buildings, structures and infrastructure suffered extensive damage due to the instability processes. In this paper, a GIS-based approach for analyzing and assessing a simplified landslide susceptibility in the Entella River catchment is presented. Starting from landslide information mainly provided from newspaper articles and unpublished reports from municipal archives, we performed a series of comparative analyses using a set of thematic maps to assess the influence of predisposing natural and anthropic factors. By evaluating the statistical distribution of landslides in different categories, we assigned weighted values to each parameter, according to their influence on the instability processes. A simplified, reproducible, but effective approach to assess landslide susceptibility in the study area was performed by combining all predisposing factors. The resulting scores in proneness to slope instability classes may be used to generate a simplified landslides susceptibility map of the catchment area which would be easy to regularly update every time a rainfall event that is able to trigger shallow landslides occurs; this would provide a useful tool for local authorities and decision makers for identifying areas which could potentially be affected by instability processes, and would help in determining the most suitable measures in land-planning and landslide risk management.