GIS-based analysis of anthropogenic coastline advances and retreats of the eastern Friuli Venezia Giulia region (NE Italy) over the past 200 years

Coasts are land-ocean interfaces of high environmental and economic value, providing essential ecosystem services and representing highly dynamic areas where natural processes interact with increasing anthropogenic pressure. As areas of intense urban and economic development, they have been widely modified, resulting in the loss of natural resources, habitats and biodiversity, and the transformation of coastal landscapes from natural to anthropogenic. The Italian coastal area is highly anthropised, with 34% of the population permanently residing in coastal cities (Mirto, 2022). The Italian coastline is approximately 8,300 km long, 13% of which is occupied by artificial structures, with an increase in coastal artificialisation of over 100 km in the last 20 years. The study area is located along the eastern coast of the Friuli Venezia Giulia (FVG) region (north-eastern Italy), facing the north-eastern Adriatic Sea, and includes the municipalities of Monfalcone, Duino-Aurisina, Trieste and Muggia. 18% of the FVG coast is considered natural, while the remainder is classified as artificial (IRDAT FVG, 2022). Anthropogenic pressures are associated with the main industrial, port and urban activities (Pagano et al., 2023). The aim of the study is to evaluate and quantify coastline changes (advances and retreats), where the coast is predominantly rocky, caused by anthropogenic activities over the past 200 years, through the analysis of maps in a GIS environment. To conduct the analysis, a series of charts and maps of the study area from the past 200 years were collected. After georeferencing the charts, past coastlines were digitised and compared with each other and with the 2025 coastline using a Geographic Information System (GIS). The areas of advances and retreats were calculated, and periods of intense coastal change were identified, with each change analysed in relation to human pressure and the intended land and sea use at the time it occurred. Between Monfalcone and Muggia, a total advance of 7.1 km² and a total retreat of 1.4 km² have been quantified. In some areas, advances reached several hundred metres, mainly due to the construction of infrastructure, ports, and industrial settlements. In Monfalcone, the greatest coastline changes were related to dredging activities for the construction of the port (retreat of 1.019 km²) and the construction of a dredged material disposal site (advance of 1.517 km²). In Trieste, the advance was mainly due to the construction of the Old Port and urban development during the 19th century, and the New Port and industrial area development during the 20th century (advance of 2.825 km²). The greatest retreat is observed in the Bay of Muggia, caused by the construction of the Zaule navigable channel (retreat of 0.141 km²) . In Duino, changes are limited, with modest advances associated with tourism and urban areas.