Geomorphological hazard and cultural heritage: a case-study of the Roman bridges in the Finalese karstic area (Western Liguria - Italy)

This study presents the geological and geomorphological surveys that relate to hazards in the Ponci Valley, considered in light of an important archaeological site from the Roman era, in order to define its state of vulnerability. This site contains the remains of Via Iulia Augusta, built along this valley 2000 years ago. Five bridges cross the road which is between 150 m and 300 m in altitude. These constitute the most important and monumental traces of the Roman communication routes in Liguria. Since the Pietra di Finale (bioclastic limestone) is largely found in this area, this rock is mainly used for building these bridges, supplemented by dolomitic limestone, quartzites and other schists. The lithological features, geomorphological evolution and morpho-structural relationships between the outcropping lithotypes caused the formation of karstic landforms and hypogeal phenomena through rainfall infiltration and underground water flow. This study highlights the geological, environmental and cultural value of this site, which is acknowledged as a "geosite" of Mediterranean importance with respect to geomorphological risk scenarios. Firm hazard reduction measures are needed, in particular related to flash floods, rockslides and sinkhole events that could affect the Roman bridge remains.