Algerian shoreline changes (1986–2024) monitored and assessed using remote sensing and GIS techniques

Abstract

This paper assesses diachronic shoreline dynamics in Algeria. To achieve this, remote sensing and Geographic Information System (GIS) techniques were employed to analyse shoreline changes over the 38-year period from 1986 to 2024. Landsat mission satellite images were processed and analysed to extract the shoreline. Following verification and validation of the extracted shorelines, their evolution parameters were calculated using the Digital Shoreline Analysis System (DSAS). Net Shoreline Movement (NSM), End Point Rate (EPR) and Linear Regression Rate (LRR) were then used to quantify erosion and accretion rates along the Algerian shoreline. The most recent Algerian shoreline extraction revealed an estimated total length of 1,683.88 km. Significant changes to the Algerian shoreline were identified: accelerated erosion between 1986 and 2000; a stabilising trend between 2000 and 2014; and general accretion during the period 2014–2024. However, this long-term analysis (1986–2024) highlights significant heterogeneity in Algerian coastal dynamics, with a net trend towards coastal erosion. Indeed, 55.4% of the shoreline has eroded, 16.64% has been stable, and 27.96% has accreted. Furthermore, the average NSM was estimated to be approximately −7.6 m, indicating moderate shoreline retreat. The EPR and LRR values were −0.201 m/year and −0.218 m/year, respectively, confirming an overall trend towards coastal erosion.