ANALYSIS OF THE EVOLUTION OF ANTHROPOGENIC COASTLINE ADVANCE BETWEEN MONFALCONE AND MUGGIA (NE ADRIATIC SEA) OVER THE LAST 200 YEARS IN A GIS ENVIRONMENT

Coasts are land–ocean interfaces of high environmental and economic value. They are the most affected areas by urban settlements and economic and productive activities, and suffer from increasing anthropogenic pressure. About 10% of the world's population currently lives in coastal areas less than 10 m above sea level, and 40% within 100 km of the coast (UN indicators: http://www.un.org/esa/sustdev/natlinfo/indicators/methodology_sheets). The anthropization process has significantly modified and altered the natural and environmental characteristics of the coastal system, affecting the structure of natural ecosystems, the quality and quantity of natural resources and changing the landscape from natural to anthropic. In Italy, the morphology of the peninsula and its geographical position in the center of the Mediterranean make the coastal areas an extraordinary resource, both from an environmental, economic and cultural point of view. The Italian coastal area is highly anthropized, with 34% of the Italian population living permanently in coastal cities (ISTAT, 2022). The Italian coastline is about 8,300 km long, 13% of which is made up of artificial structures such as ports, hydraulic and coastal protection structures. In the last 20 years, 5 km of natural coastline has been lost every year due to the construction of new artificial structures (ISPRA, 2020). The study area is located in the Gulf of Trieste, a shallow semi-enclosed sea of about 500 km2 in the north-eastern Adriatic Sea, in the Italian region of Friuli Venezia Giulia (FVG). The FVG coastline are 111 km long, and the 55.4 % is highly anthropized (Fig. 1) (Zanchini et al, 2017). In the northern part of the gulf the coasts are characterised by beaches of fine or pebbly sand. In the eastern part, the coast is rocky, with narrow, pebbly and gravelly beaches (Brambati and Catani,1988), constituted by Eocene marls and sandstone of the Trieste formation and Cretaceous and Paleocene limestones. The coastal area near Trieste has been heavily modified by anthropogenic interventions that have altered both the natural coastline and the seabed. The southern part has rock coasts at the foot of abrasion escarpments, with several bays, such as those of Koper and Muggia. The aim of the study is to evaluate and quantify the evolution and the changes (advances) of the coastline and the consequent loss of the marine (littoral) environment and ecosystem between Monfalcone and Muggia, where the coastline is predominantly rocky, caused by anthropic activities over the last 200 years. To carry out the analysis, a series of historical charts of the study area from the last 200 years were collected. After georeferencing the charts, the past coastlines were digitized and compared with the current ones using the Geographic Information System (GIS). For example, Fig. 1 shows two of the past digitized coastlines, the one from 1922 and the one from 1927. The whole evolution of the coastline was analyzed, relating each change to the cause that produced it and the time period in which it occurred. The analysis highlighted that in some areas the advances caused by human activity were even hundreds of meters, mainly due to the construction of infrastructures, ports and industrial settlements. The only retreated section was in the Bay of Muggia (Fig. 1), where the changes were caused by the construction of a navigable canal. A good understanding of the rates of historical changes is a prerequisite for effective coastal zone management. Only by examining the risks and potential consequences it is possible to find high-quality and innovative solutions to protect the coasts and the social and economic activities based on them.