Qualitative and quantitative evaluation of the influence of anthropic pressure on subsidence in a sedimentary basin near Rome

This paper presents the results of analyses measuring variations in anthropic pressure and the influence of anthropic pressure on the variations in subsidence rates from 1954 to 2005 in the Tivoli-Guidonia area, located to the East of Rome, Italy. In the last 60 years, this area underwent exceptional demographic growth, as well as an increase in the quarrying and hydrothermal industries. The calculation of the increase in anthropic pressure was based on two factors: the expansion of built-up areas and the increase in quarrying. Photogrammetric techniques permitted a multi-temporal analysis of aerial photos taken in 1954, 1985, 1993, 1998 and 2005. The aim of this analysis was to estimate the increase in both urban surface area and travertine quarrying. Non-conventional techniques, such as the reconstruction of photograms using photo retouching software, allowed for the use of aerial photos from 1954. These photos were fundamental for establishing a medium-term evaluation of anthropic activity in the area. The results of the photogrammetric analysis were compared to the phases of acceleration and stabilization in subsidence phenomena, deduced from a RADAR interferometry study published by the Italian Ministry of the Environment. This comparison showed a close relationship between the rise and temporary halt of anthropic development and the rise and fall of subsidence rates. Furthermore, data on the distribution of private wells in the study area, variations in the groundwater table level and the precipitation regime were analyzed, but, although helpful in defining the geological context and considerable transformations of the territory, they were considered as qualitative data due to the lack of systematic measures or an unclear relationship to the variations in subsidence rate. Despite the difficulties involved in evaluating both the amount of anthropic pressure and the role of different human activities on environmental change, it was possible to estimate the variations in anthropic pressure and their influence on potentially dangerous geological processes.