Socioeconomic vulnerability of a Mediterranean coastal lagoon : case of Ghar El Melah, Tunisia

The coastal lagoon system is undergoing pronounced shoreline retreats and floods as a consequence of the ongoing sea level rise resulting from global warming. The aim of this study is to assess shoreline changes, land use occupation and to evaluate socioeconomic vulnerability in the urbanized coastal lagoon in Ghar El Melah, Tunisia in central Mediterranean. Methods are based on the diachronic shoreline changes monitoring from satellite scene, aerial photograph, topographic, and bathymetric maps during the period 1882, 1936, 1974 and 2021. Shoreline movement is acquired according to the statistical Digital Shoreline Analysis System (DSAS) from 1882 to 2021 data sets. Land use classification was established from supervised algorithm using multiple satellites scenes of Landsat 5 (1985) and Landsat 8 (2021). The Socioeconomic Vulnerability Index (SVI) is calculated from five socioeconomic parameters: (1) population density, (2) land use, (3) coastal fishing (4) road network and (5) settlement. Our results reveal alarming erosion of the sandy barrier with a maximum value of Net Shoreline Movement (NSM) − 1580 m (± 6 m) between 1882 to 2021. Temporal classification of the Ghar El Melah landscape from 1985 to 2021 revealed the extended urban class over the lagoon internal ridge from 5.4% to 14 % respectively. Whereas the vegetation crops are decreasing by 10%. The statistical coastal (SVI) map reveals that 87% of the lagoon area are characterized by high to very high vulnerability (class 5). These high coastal vulnerabilities risk is primarily induced by the extensive land occupation since the last few decades.