Multi-scenario analysis of debris flow propagation on the archaeological site of Villa Romana del Casale (Sicily, Italy)

The cultural heritage of a nation represents its historical memory and its identity character, playing an important role in the economic, cultural, recreational and tourism sector of the country. However, numerous studies show that cultural sites, including historic buildings, city centers and archaeological sites, are exposed to natural risks. In particular archaeological sites are extremely vulnerable to extreme rainfall flooding and debris flow events and other associated natural phenomena, such as debris flows. The effects of different representations of the geometry of the archaeological area are evaluated through two-dimensional numerical modelling of debris flow propagation. The case study is represented by the archaeological site of Villa Romana del Casale in Piazza Armerina (EN), a UNESCO heritage site since 1997. A multi-scenario analysis is proposed to consider triggers of debris flows, upstream of the archaeological area. The results allow us to evaluate how different combinations of landslide events interact with the historical building. The impacts are evaluated in terms of arrival times of sediment flows at the archaeological area and of the volumes of debris and residual debris deposited at the site. Effectiveness of existing hydraulic defence works is also assessed. The results show that detailed modelling of the geometry of thestructure, with the inclusion of the perimeter openings, is crucial not only for estimating the risk in the internal areas of the Villa but also for avoiding overestimation of debris flows outdoors of the archaeological site. • Large and small scale 2D modelling of debris flows impacting archeological sites. • Modelling historical buildings as closed block allows the estimate of arrival times. • Actual risk for cultural heritage needs proper modelling of the perimeter openings.