Determination of Coastal Erosion Rate from Multitemporal Landsat Data at Barra Beach, Southern Mozambique

Abstract

This study analyzes the shoreline dynamics at Barra Beach, located in southern Mozambique, over a 24-year period. The main objectives were to quantify rates of coastal accretion and erosion and to identify key drivers of shoreline retreat. We utilized Landsat imagery, processed with the Google Earth Engine (GEE), to generate annual median composites, from which shoreline positions were extracted. These were then analyzed using the Digital Shoreline Analysis System (DSAS), applying the Weighted Linear Regression (WLR) method to compute rates of change. Our results indicate that 65.4% of transects exhibit erosion, with an average shoreline retreat rate of –2.72 m/yr (standard deviation of 3.18 m/yr). In contrast, 34.6% exhibit accretion, with an average progradation of 1.48 m/yr (standard deviation of 2.57 m/yr). The most extreme erosion rates (WLR = –11.02 m/yr) occurred in zones of intense tourism, where dune vegetation removal has compromised the natural buffer against marine intrusion. In conclusion, Barra Beach is undergoing predominantly erosional processes, albeit with considerable spatial variability. These findings underscore the urgent need for targeted mitigation strategies to enhance the region's coastal resilience and to preserve its environmental integrity.