Francesca Vergari

The Aeterna Urbs Geomorphological Heritage (Rome, Italy)

The largest European cities are characterised by millennia of urbanisation. ‘Man-made layering’ over time has modified the original natural setting on which these cities have developed, but an expert eye can often still recognise the ancient geomorphological features of the landscape. We show an example of the identification of the original geomorphological characteristics of the landscape over which the city centre of Rome developed, by means of a geomorphological survey conducted in this urban environment. The aim of the analysis is the enhancement of geotourism in the city centre, by describing the palaeogeography of ancient Rome through the landforms that are still visible. The geomorphological survey led to the identification of two geomorphosites. We developed an evaluation model of the Geotourist Value of a Site (VSG index), which consists of the quantification of five fundamental attributes for a geosite, characterizing its scientific and geotourist interests. The VSG index produces an order of priority for geosites for their enhancement. These results are transferred to the proposal for a geotourist itinerary, along which the selected geosites are joined and related to the historical and cultural features of the city. The itinerary is also represented on a geotourist map, created through the union of scientific and popularised electronic devices. The major outcome of this study is to supplement a proposal for the developing the historical and cultural tourism of the Aeterna Urbs combined with its natural environment features, highlighting the importance of the close connection between these themes.

Geomorphological classification of urban landscapes: the case study of Rome (Italy)

ABSTRACT The results of a long-lasting geomorphological survey carried out in Rome are summarized. A method aimed at integrating survey data, historical maps, aerial photographs and archaeological and geomorphological literature produced a geomorphological map of the present-day historical centre. The geomorphology of Rome is related to the paleogeographical conditions prior to the founding of the City; they allow us to recognize the stages of landscape evolution of the ancient Caput Mundi (Capital of the World). The study area has been affected by continuous man-made changes to the drainage network and to the topographic surface over the last 3000 years. It has forced the authors to develop innovative solutions to undertake effective analysis of the urban environment and the legend of the geomorphological map in this peculiar context. The resulting map is useful for urban planning and archaeological research.

Assessing soil erosion hazard in a key badland area of Central Italy

Abstract In this work, an integrated methodology was applied to assess the water erosion hazard in Upper Orcia Valley, an area of Southern Tuscany (Italy), greatly affected by severe denudation processes, that caused the development of widespread badlands. Prediction of areas prone to calanchi badland development was carried out by applying a susceptibility assessment method based on conditional statistical analysis, preceded by a bivariate statistical analysis aimed at selecting the most influential causal factors of erosion. Water erosion rates at badland sites were estimated by means of an empirical statistical method, implemented to evaluate the erosion intensity (Tu denudation index) and based on some geomorphic parameters as independent variables. This methodology allows associating the denudation intensity to the spatial prediction. The validation procedure, based on a random partition of calanchi badland areas, confirmed the efficiency of the spatial zonation of the erosion hazard values. Moreover, the comparison of the estimated erosion rates with the results of decadal investigations on denudation processes affecting the study area, performed by different monitoring methods, showed the effectiveness of the estimation model. These results allowed concluding that the proposed procedure represents a useful tool to be applicable for soil protection strategy planning in land management of Mediterranean areas characterized by similar morphoclimatic features, even when direct erosion rate measures are not available.

Geomorphodiversity index: Quantifying the diversity of landforms and physical landscape

The physical landscape is the mosaic resulting from a wide spectrum of environmental components. The landforms define the variety, or diversity, of the geomorphological component: the geomorphodiversity. Landforms are usually represented in thematic maps where the scale and the graphic solutions are widely heterogeneous. Since geomorphological maps are not always easy to obtain and standardize, topography might be used as a proxy to infer the morphological signature. To recognize, evaluate, and in some cases promote the geomorphodiversity of an area, a numerical assessment is preferable. Through the use of quantitative approaches, indexes can be defined which quantitatively characterize the physical landscape in a discretized space consisting of continuous and regular cells. In this approach each cell is labelled with an algebraic value, which increases with the diversity degree. In this paper a quantitative index for geomorphodiversity is estimated stressing the topographic variables derived from Digital Elevation Models in a GIS environment. The resulting index is the sum of the variety of each terrain parameter taken into account. The areas characterized by the highest value of geomorphodiversity index show a good correspondence with well-known situations in the region where not always the geological heritage is properly acknowledged. The areas characterized by the lowest value of geodiversity correspond to the center of some intermountain basins of the region. Being the index strictly related to the topographic variety, this result is quite obvious but not easily predictable since in some flat areas the index is higher. Comparing the results with the geomorphological map of the area performs a validation procedure for the method. A positive correlation is found between the index calculated and the presence/absence of landforms. The paper shows that the index is a useful and simple tool for the identification, analysis and promotion of the geological heritage.

Contribution for an Urban Geomorphoheritage Assessment Method: Proposal from Three Geomorphosites in Rome (Italy)

Abstract Urban geomorphology has important implications in spatial planning of human activities, and it also has a geotouristic potential due to the relationship between cultural and geomorphological heritage. Despite the introduction of the term Anthropocene to describe the deep influence that human activities have had in recent times on Earth evolution, urban geomorphological heritage studies are relatively rare and limited and urban geotourism development is recent. The analysis of the complex urban landscape often need the integration of multidisciplinary data. This study aims to propose the first urban geomorphoheritage assessment method, which originates after long-lasting previous geomorphological and geotouristic studies on Rome city centre, it depict rare examples of the geomorphological mapping of a metropolis and, at the same time, of an inventory of urban geomorphosites. The proposal is applied to geomorphosites in the Esquilino neighbourhood of Rome, whose analysis confirm the need for an ad hoc method for assessing urban geomorphosites, as already highlighted in the most recent literature on the topic. The urban geomorphoheritage assessment method is based on: (i) the urban geomorphological analysis by means of multitemporal and multidisciplinary data; (ii) the geomorphosite inventory; and (iii) the geomorphoheritage assessment and enhancement. One challenge is to assess invisible geomorphosites that are widespread in urban context. To this aim, we reworked the attributes describing the Value of a site for Geotourism in order to build up a specific methodology for the analysis of the urban geomorphological heritage.

Multi-method Evaluation of Denudation Rates in Small Mediterranean Catchments

The paper presents the results of the research tasks of the Quantitative Geomorphology Working Group (of the Italian Association of Physical Geography and Geomorphology) focused on multi-method evaluation of denudation rates in small catchments of Italy. Several study areas are compared with the goal of quantifying the morphodynamic evolution in different response times and with traditional and innovative techniques. The final aims are the direct erosion monitoring, the geomorphic analysis for the comprehension of drainage basin morphodynamics, up to the geomorphological hazard evaluation. The catchments are key Mediterranean areas particularly sensitive to climatic and anthropic modifications. The efforts of the Working Group are finalized to favour scientific collaboration activities among members with the aim of strengthen the potential of Quantitative Gomorphology in morphodynamic studies.

The Potential of Permanent Gullies in Europe as Geomorphosites

Geotourism is a useful way to educate societies in the field of geomorphology and related natural hazards. Geosites, including geomorphosites, represent the basis for the development of this type of tourism. This study describes 12 representative gully regions within nine European countries. The characteristics of 42 permanent gullies, gully systems, and badland landscapes are presented. Based on scientific values of the sites, educational lessons to be learned were identified that are mainly related to (i) gullies as a geological window, (ii) present-day geomorphological processes and (iii) stages of historical gully erosion reflecting past human–environment interactions. To evaluate possible education activities, a geotouristic assessment of the studied gullies and badlands was made, based on scientific, educational, functional and touristic indicators. This assessment demonstrates a large difference between the selected gully and badland sites, particularly with regard to functional and tourist values. The geotouristic potential of gullies (badlands) is the highest in Italy and Spain and the lowest in Romania and Latvia. In some countries, permanent gullies are not regarded as geotouristic attractions at all, while in others, they constitute a significant element of their tourism development strategy. In our opinion, all activities must be part of a broader strategy for the development of geotourism in gully and badland regions, for example, gullies may be included as geosites within existing or planned geoparks.

Estimation of the thickness of anthropogenic deposits in historical urban centres: An interdisciplinary methodology applied to Rome (Italy)

In historical urban centres, the superimposition of excavation and deposition activities over time has resulted in an irregular spatial distribution of anthropogenic deposits, which may reach considerable thicknesses. The detection of those thicknesses requires extensive investigations. Broad borehole and geophysical campaigns cost time and money, consequently at the urban-planning level, it is usual to shift to an estimation of thicknesses, which may be performed through map-algebra operations, that is, by subtracting from the modelled ground surface the elevation of the anthropogenic-deposit basal surface. The latter is implemented through the interpolation of point elevation data, which are generally provided by borehole logs. Despite the development of advanced spatial interpolation methodologies, previous modelling results in the literature show that if the process is affected by insufficient input data, it produces imprecise interpolation outputs. This paper reports an interdisciplinary methodology aiming at enhancing elevation datasets, in order to obtain more accurate digital elevation models. The increase in number and spatial distribution of input points is achieved through past-landscape analyses mainly based on elevation data given by borehole logs, available archaeological reports and historical topographic maps, these being generally available for historical urban centres. The methodology was tested in an urban sector of Rome, where significant activities have been performed for millennia particularly during the Roman Age. A reliable model of the basal surface of the anthrostrata led to a better estimation of the spatial distribution of such deposits and, in addition, revealed the original topographic surface, as modified by human activities.

The Role of Lithology

Abstract Badlands can develop on bedrock and/or weathered material, the characteristics of which play a key role on hillslope processes in a range of climate conditions. Therefore, fundamental attention should be given to badland materials, the main features of which are grain size, clay mineralogy and physico-chemical characteristics. The typical weathering profile consists of crust, subsurface and unweathered material, but depending on climatic, lithological, topographic and hydrological factors, the properties and appearance of both surface and subsurface materials change over time. Through time, regolith formed on erodible and dispersive bedrock materials tends to stabilize, again as a function of slope and climate conditions because prolonged precipitation can cause decrease in surface strength and runoff and reduce the dispersivity of the surface. Vegetation also has distinct role in stabilizing the clayey sediments due to lowering the dispersivity in the upper horizon of the badland material, even though such stabilization is often not permanent and erosion processes can sometimes reoccur. Finally, all the above cited factors and properties of badland materials play a complex and key role in the development of different geomorphic processes and related landforms.

The use of the slope-area function to analyse process domains in complex badland landscapes: Process domains in complex badland landscape

This paper explores the effectiveness of the widely-used functional relationship between drainage area (A in m) and slope (S in m/m) to identify local process domains and aid interpretation of process interactions in a complex badland landscape. In order to perform this investigation, a series of sub-basins tributary to the Formone River in the Orcia catchment (central Italy) were selected as a suitable study area within which to explore our questions, given these basins’ general representativeness of local terrain, the availability of a high resolution digital terrain model and previous extensive geomorphological research. Eroding basins containing both calanchi and landslides are common in the sub-humid badland landscape of central Italy, where field observation identifies a complex pattern of erosive processes associated with a history of uplift, despite which parts of the local landscape appear disconnected. Results reveal that the shape of all S–A curves (plotted using S data binned on log A) is comparable with that described in the literature, although sub-basins containing calanchi generally plot with higher S values than non-calanchi ones, except in the ‘fluvial’ section of the plots. Second, when viewed on total data (non-binned) S–A plots, landslide source area domains and calanchi domains are entirely coincident in all basins, supporting a cause–effect relationship. Additional plotting of the frequency characteristics of the raw data in a new way supports the interpretation that calanchi frequently initiate in landslide scars. In general though, although the S–A plots can contribute to the disentanglement of geomorphological behaviour in some complex erosional landscapes, it became apparent that in this landscape, process domains do not separate out with clarity along the A axis as suggested by theory. Despite this, an alternative, broader-scale morphoevolutive model can be proposed for the development of within-landslide calanchi, driven by changes to basin connectivity to the base channel.