Anthropogenic sinkholes in Rome are mainly linked to the presence of a dense network of underground cavities. These cavities are tunnels produced by ...
ACCADEMIA NAZIONALE
DEI
LINCEI
CONVEGNO
Resilienza delle città d’arte alle catastrofi idrogeologiche: successi e insuccessi dell’esperienza italiana ROMA, 4 - 5 NOVEMBRE 2014
DOCUMENTO FINALE
An important hydro geological catastrophe in Rome: the sinkholes phenomena.
Ciotoli G.* & Nisio S.**
*CNR-IGAG – Rome ; ** ISPRA- Geological Survey of Italy
Anthropogenic sinkholes in Rome are mainly linked to the presence of a dense network of underground cavities. These cavities are tunnels produced by historical mining activities, well, drainage tunnels and catacombs linked to a history of more than two thousand years. The presence of cavities may easily trigger the collapse of the shallow or deeper layers. Subordinate causes are associated to the loose of soil below the road surface linked to run-off phenomena concurrently with intense rainfall. Over the last decades, an increase in the occurrence of these collapses in the urban center determines risk conditions to citizenship, as well as disruption of roads and underground networks (sewers, water systems, electricity, telephone, etc.). Furthermore, the aspects related to the preservation of cultural heritage and of underground sites of historical and archaeological importance should be considered. Since 1875, 2600 anthropogenic sinkholes are censed in Rome. In this scenario the applicability of the concept of sinkhole risk is extremely difficult due to the lack of data about return times, and thus it is not possible to calculate probabilities of the event in a given time horizon. Then the concept of risk has been replaced with the most generic concept of susceptibility, which eliminates the probability term related to time, and defines the "risk" in spatial terms only: a collapse could occur in a certain area in an infinite time interval, and a certain area has characteristics that facilitate a collapse. In this work a methodology has been proposed to individuate the density of underground cavities and a susceptibility of the urban territory to the sinkholes. It includes the construction of a probabilistic model based on the evaluation of the statistical relationships between the known collapses and a group of conditioning factors (i.e., presence of unfilled cavities, adequate hydrological conditions, sediments prone to subsidence) by using Logistic Regression. In this way collapse susceptibility maps can be produced identifying the sinkhole prone areas in the Rome territory.
