Geomorphological hazard and tourist vulnerability along Portofino Park trails (Italy)

International audienceThe many trails existing in the coastal area of Portofino Promontory are used by tourists for trekking or as pathways to small villages and beaches. The aim of this paper is to define geomorphological hazard and tourist vulnerability in this area, within the framework of the management and planning of hiking activities in Portofino Natural Park. In particular, processes triggered by gravity, running waters and wave motion, affecting the slopes and the cliff, are considered. The typology of the trails and trail maintenance are also taken into account in relation to weather conditions that can make the excursion routes dangerous for tourists. In conclusion, an operative model is applied for the definition of possible risk scenarios. This model is founded on an inventory and the quantification of geomorphological hazards and tourist vulnerability, in comparison with trail rescue data. The model can be applied to other environments and tourist areas

Man-made activities and morphological changes of Ligurian floodplains (Italy) since modern history to nowadays: an approach through old maps comparison

The Tyrrhenian slope of Liguria extends along the coast, from West to East, for nearly 300 km between Ventimiglia to Marinella di Sarzana: this stretch of territory presents more than a hundred catchments mainly characterized by small-size floodplains, usually less than 1 km2. Ligurian catchments, except for the Roja and the Magra rivers, have common features: by the area they can be distinguished in small basins (less than 15 km2), medium (15-150 km2) and large (150-500 km2). The slopes of the catchment areas are very steep, while the flat alluvial plains are typically narrow and elongated: the largest one are referred to the Entella stream (approximately 4 km long) and the Centa stream (about 7 km in length). On these floodplains are located almost Ligurian urban areas, which represent the expansion of the historical settlements and road connections. Through a comparative mapping it was rebuilt the morphological evolution of Ligurian floodplains in historical times, witnessing the land-use and riverbed changes in the modern era until today, by using: 1) Historical maps of the eighteenth century by Matteo Vinzoni (\u201cPianta delle due riviere della serenissima Repubblica di Genova divise nei commissariati di sanit\ue0\u201d e \u201cIl Dominio della Serenissima Repubblica di Genova in terraferma\u201d); 2) historical topographic maps of the first half of the nineteenth century (\u201cStati Sardi di Terraferma), in different topographic scales: a) 1:50.000, b) 1:20.000 and c) 1:9.450; 3) historical topographic maps of the second half of the nineteenth century until the first half of the twentieth century (\u201cTavolette dell\u2019Istituto Geografico Militare Italiano, Firenze, 1878-1940, 1:25.000); 4) regional maps for the second half of the twentieth century, 1: 10.000 and 1: 25.000, while the current status was assessed with Google Earth Pro platforms; 5) important information was taken by the Map of the historical evolution of urban fabric, 1: 50.000 produced by Liguria Region and obtained by the overlap of urbanized areas in different periods (1855, 1936, 1964 and 1986). The secular human activities have therefore modified the natural landscape through land use changes, either for catchment or for the floodplain. The main channel, and even the minor hydrographic network, have showed major transformations over time. The anthropic action has deeply modified the morphology of Ligurian floodplains, except for the two largest: Albenga (Centa stream) and Chiavari-Lavagna (Entella stream), which still have a portion of soil for agricultural purposes. In many cases it has detected a river-bed covering, especially in the medium-terminal portion, for the purpose of building needs and the road link. Other very widespread changes finally concern: a) deviations and displacements of the riverbed, b) the progradation of the coastline due to fills and embankments

Geosites and geological landscapes of Liguria (Italy)

Liguria is a small region in Northwestern Italy which is characterized by significant and valuable geoheritage. The 1:250,000 map presented in this paper displays the 120 geosites of Liguria, officially approved by regional and national authorities, framed in the context of the geological landscapes of the region. The geological landscapes were obtained by categorizing and thematizing geological, lithological and geomorphological data in macro-units with similar characteristics. Protected areas (National parks, regional parks and natural reserves) and caves are also highlighted in the map. This work aims to give a better understanding of the Ligurian geoheritage, its relationship with the geological and geomorphological context, and the framework of protected areas. Thus, the present map can be a useful tool for developing effective geoheritage management and enhancement strategies

Culverted rivers in the historic center of Genoa (Italy) as an emblematic case of human pressure and fluvial landscape changes

The city of Genoa is internationally known its the recurrent floods, mainly related to the Bisagno River. The high risk is linked to meteo-hydrological hazard and to the urbanisation in hazardous areas and consequently to the high exposure of risk elements. The present research concerns the hydrographic network that characterises the historical center of Genoa, i.e. the natural amphitheatre bordering the Polcevera valley to the W and the Bisagno valley to the E. In this area of just 8.5 km2 there are eight catchments ranging from 0.49 km2 to 2.36 km2 in size: from W to E we recognise the basins of the San Bartolomeo, San Lazzaro, San Teodoro, Lagaccio, Sant'Ugo, Carbonara, Sant'Anna and Torbido streams. These watercourses have been subject to anthropic modifications since the Middle Ages, sometimes with significant diversions, rectifications and channelling; today the watercourse network appears almost entirely artificial, flowing under the streets and buildings of the historic centre. The name of some alleys recalls their presence, which is otherwise not perceptible. Only the upper basin of the Lagaccio and San Lazzaro streams still have a watercourse with a natural riverbed, although the area is still significantly urbanised. The construction of these culverts over time and the modifications they have undergone over the following centuries up to very recent times due to progressive urbanisation have led to a reduction in the hydraulic cross-section, which can lead to a possible flow of water under pressure and the consequent flooding hazard. Therefore a better geographic knowledge of these culverted streams in Genoa historical city is crucial for hazard and risk assessments and for the planning of related hydraulic risk reduction activities

Urban geomorphology of Genoa old city (Italy)

A multi-year geomorphological surveys of the city of Genoa allowed the creation of an original geomorphological map of the urban environment. The city of Genoa is internationally known for the importance of its port and for the presence of a historic city center recognized as an UNESCO World Heritage since 2006. The research methodology was based on the structuring and analysis of a multi-source geodatabase consisting of information acquired from scientific literature and technical reports, historical and recent photographs and maps, geological and environmental data related to land planning plans, original data from field surveys. Work phases of data elaboration included: 1) a multi-temporal cartographic comparison from the eighteenth-century to year 2016; 2) an analysis of aerial photographs in the period 1936-2016; 3) the interpretation of boreholes data; 4) both surface and underground geomorphological observations within the city centre, by means of field surveys and speleological techniques. The recognition of the former geomorphological setting on which the historical nucleus of Genoa has developed, and the interpretation of its paleogeographic, geological and tectonic conditions, are not an easy task: since the High Middle Ages of the Maritime Republic of Genoa, the superposition of multiple phases of urban sprawl has obliterated original geomorphic conditions. However, interpretation of the rich geodatabase allowed to classify landforms, processes and surficial deposits with respect to their original environment and morphogenesis, i.e due to: running waters, gravity, karst, action of the sea; but, above all, due to human activities. In fact, the entire study area has undergone continuous modifications by man through the all considered time interval, as shown by artificial land fillings at the seaside, alteration of the river network, excavations and fills on the slopes, with the highlighting of significant anthropogenic urban landforms. The geomorphological map support both a morpho-evolutionary and a functional approach to the geomorphological landscape the of Genoa old city: therefore, it can be a useful tool for land planning, also aimed at reducing the geo-hydrological risk that characterizes the urban area

Geo-hydrological risk mitigation in a terraced landscape: LiDAR data analysis in the Portofino natural Park, Italy

Modification of steep slopes with man-made terraces is an ancient and widespread habit in many areas of the world. If the modification assures agricultural practices in mountainous areas, it results even as an important interference with the geomorphic processes: important quantities of soil and sediments are subtracted to the degradation processes and, in case of total abandonment of terraces, they result again available to erosion. Intense rain event may cause partial instability or even collapse of the anthropogenic structures, configuring terraces as an additional source of Geo-hydrological hazard. Recent events in Liguria - northern Italy, in Cinque Terre 2011 and Leivi (Chiavari) 2014, caused damages and even casualties due to the sudden collapse of terraced slopes. A crucial point in assessing the potential hazard caused by abandoned terraced slopes is identifying their real extension. LiDAR data analysis is an important assessment tool particularly in strong steepness areas due to the capability of recognizing linear regular structures. In the present research LiDAR data analysis has been used to identify terraces in the Portofino Natural Park area (Liguria region, Italy) as one of the preliminary activities of the RECONECT European Union\u2019s Horizon 2020 Research and Innovation Programme project. The project plans to realize nature based solutions to mitigate geohydrological risk in two pilot areas in the Portofino promontory and the recovery of terraces is one of the foreseen actions. Mapping terraces is the first step to evaluate the potential risk associated to the possible instability processes and the interventions to be realized. Land use evolution in the area from 1800 to present have been indeed found through historical maps examination and used in conjunction with LiDAR analysis results

RAPPRESENTAZIONE IN CARTA DELLE CARATTERISTICHE DEI SENTIERI AI FINI DELLA MITIGAZIONE DEL RISCHIO GEOMORFOLOGICO

L’ambiente naturale di alcuni particolari ambiti geografici è in rapida evoluzione non solo per quanto riguarda le sue variabili, legate alle tendenze climatiche in atto, ma anche in relazione all’aumentata frequentazione turistica. La maggiore diffusione dei mezzi di risalita in montagna e di navigazione lungo le coste, rende possibile l’accesso anche a siti altrimenti difficilmente raggiungibili: ciò porta ad un contatto rapido e diretto con ambienti talvolta mutevoli in tempi brevi. La crescente richiesta di una maggiore conoscenza dell’ambiente naturale, che si esplica per lo più attraverso la frequentazione della rete sentieristica, implica la necessità di abbinare alle proposte di percorsi ed itinerari, note illustrative e carte tematiche di immediata lettura, che evidenzino sia i siti di interesse naturalistico - culturale sia le possibili situazioni di rischio e di difficoltà di percorrenza degli itinerari stessi. Esistono infatti alcuni elementi morfologici del territorio che di per sé non costituiscono una pericolosità in senso stretto ma che, a seconda delle capacità del fruitore, possono essere fonte indiretta di danno, in quanto rendono difficile l’attraversamento di alcuni punti specifici o la percorrenza di particolari tratti di sentiero. Contemporaneamente la stagionalità in alcune regioni climatiche e la variabilità meteorologica possono incrementare sia la pericolosità sia la vulnerabilità e di conseguenza il rischio per il frequentatore. Obiettivo del presente lavoro è quello di proporre una simbologia adeguata da inserire sulle carte dei sentieri, e più specificatamente su quelle geoturistiche, per una rapida e facile identificazione di specifiche situazioni riscontrabili lungo itinerari: questi simboli, che dovranno riferirsi solo alla percorribilità dell’itinerario e non alla valorizzazione naturalistica dello stesso, andranno rappresentati su base topografica separata, al fine di non appesantire la lettura dell’elaborato cartografico principale e dovranno fornire solo informazioni oggettive che saranno poi interpretate dal fruitore dell’itinerario. La simbologia e le note terranno conto sia delle caratteristiche costanti dei sentieri che degli elementi variabili, in funzione anche delle condizioni climatiche o stagionali, a seconda dei diversi ambienti interessati

Metasomatism induced by alkaline magma in the upper mantle of northern Victoria Land (Antarctica): an experimental approach

Magma generation in the Ross Sea system is related to partial melting of strongly metasomatised mantle sources where amphibole most probably plays a crucial role. In this context, metasomatism induced by a mela-nephelinite melt in lithospheric mantle of the Mt. Melbourne Volcanic Province (northern Victoria Land – NVL, Antarctica) was investigated experimentally studying the effects of melt interaction with lherzolite at 1.5-2.0 GPa and T=975-1300°C, and wehrlite at 1.0 GPa and T=1050-1250°C. The experiments were designed to induce melt infiltration into the ultramafic rocks. The observed modifications in minerals are compared with those found in mantle xenoliths from NVL. The effects of metasomatic modifications are evaluated on the basis of run temperature, distance from the infiltrating melt and on the diffusion rates of chemical components. Both in lherzolite and wehrlite, clinopyroxene exhibits large compositional variations ranging from primary diopside to high Mg-Cr-(Na) augitic and omphacitic clinopyroxenes in lherzolite, and to low Mg and high Ti-Al-Fe-Na augites in wehrlite. Olivine (in wehrlite) and spinel (in lherzolite) also result compositionally modified, the former shows enrichments in Fe, the latter displays a higher Cr/(Cr+Al) ratio. The systematic variations in mineral compositions imply modifications of the chemistry of the infiltrating melt as recorded by the glass veinlets and patches observed in some charges. In experiments involving wehrlite paragenesis, the glass composition approaches that of melt patches associated to both amphibole-free and amphibole-bearing natural samples, and is related to olivine+clinopyroxene crystallisation coupled with primary clinopyroxene dissolution at the contact between the metasomatising melt and the solid matrix. Even if amphibole crystallisation was not attained in the experiments, we were able to explain the occurrence of amphibole in the natural system considering that in this case a hot metasomatising melt infiltrates a cooler matrix