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

Abstract

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.

Urban geomorphology of a historical city straddling the Tanaro River (Alessandria, NW Italy)

“…Some very recent researches concerning urban geomorphology were carried out in a number of Mediterranean cities, in terms of geomorphological mapping, geomorphological heritage and characterization of anthropogenic landforms (Brandolini et al, 2018(Brandolini et al, , 2019Del Monte et al, 2016;Luberti et al, 2018Luberti et al, , 2019Mozzi et al, 2018). Most of these case studies are located in alluvial-coastal areas with more or less pronounced hills behind them (Brandolini et al, 2017(Brandolini et al, , 2018Luino et al, 2019;Roccati et al, 2019).…”

Geomorphology of the historic centre of theUrbs(Rome, Italy)

“…professionals and companies, archives, literature) were fundamental to detect the most ancient modifications not recorded by historical maps (methododological guidelines in papers e.g. : Brandolini et al, 2019;Luberti et al, 2018Luberti et al, , 2019Mozzi et al, 2018). The archaeological records provided many local, but essential insights into the man-made and infilled ground, whereas historical documentation (e.g.…”

“…the Roman-age Urbs within the ancient walls. Regarding this area, according to previous experiences in historical centres (Luberti et al, 2019, and references therein), a fundamental role towards the detection of anthropogenic modifications was played by the analysis of archaeological and historical data, which were matched with those provided by the data collected from both geognostic and geoarchaeological investigations. Citing three examples among several, previous researches highlighted how the archaeological facts regarding Circus Maximum and Tiberina Island have allowed to infer the palaeogeographical conditions present when Rome was founded (Del Monte et al, 2013), or the archaeological data on ancient marshy areas supported the reconstruction of the natural drainage network in the city centre (Luberti et al, 2018); moreover, the genesis of the Monte della Giustizia is related to the construction, since the 6th century BC, of a huge military-defence system, including walls (Servian Walls), a moat and an embankment, which elevated the previous structural surface at the top of the Esquiline hill as the highest relief of Rome on the left side of the Tevere (Luberti & Del Monte, 2020;Pica et al, 2017).…”

The Turin fluvial terraces as evidence of the new Holocene setting of the Po River

“…River embankments, bank defences, walking routes (locally named Murazzi) and boarding for the river navigation, combined with the accumulation of large quantities of anthropic deposits, diffusely cover the natural Po terraces. Similar sediments also characterize the setting of other cities (Del Monte et al, 2016;Luberti et al, 2017Luberti et al, , 2019. Modification of the natural scarps, essentially finalized to level the urban flowing roads, is particularly common (Forno & Lucchesi, 2014).…”