Semi-automated shoreline extraction applied to estuarine coasts: A case study in the Río de la Plata estuary, Argentina

Abstract

Estuaries are dynamic coastal water bodies where river outlets meet the ocean, influenced by river and groundwater inflows, tidal forces, wind, and wave action. Climate change and human activities can accelerate sedimentary processes, impacting on the evolution of coasts. In this sense, remote sensing has become crucial for monitoring morphological changes, an asset that is essential for effective coastal management. The Río de la Plata (RdlP) estuary, covering an area of 35,000 km 2 , is one of the world’s most significant estuaries. Comprehensive long-term erosion analysis is challenging due to its extensive coastline. This study employs VedgeSat, a toolkit derived from CoastSat which utilizes Google Earth Engine database and processing capabilities to semi automatically extract shorelines from publicly available satellite images. This study aims to analyze shoreline changes over the past 40 years in the middle RdlP estuary to calculate change rates, compare them with previous studies, and evaluate the tool’s suitability for estuarine environments. In this study 550 shorelines were extracted for the period from 1984 to 2023 and were subsequently analyzed using the Digital Shoreline Analysis System (DSAS) to obtain net shoreline movement (NSM) and linear regression rate (LRR). The long-term shoreline analysis reveals distinct patterns of erosion, stability, and slight accretion with LRR and NSM averaging 1.6 m/yr, and 97.9 m, respectively. Decadal analysis identified changes in evolutionary trends, showing heterogeneous behavior along the studied area. Negative rates and coastline retreat predominate from 1984 to 2003, while slightly positive rates and accretion are observed from 2003 to 2023. Long-term monitoring performed utilizing tools like VedgeSat has proven valuable for understanding coastal change patterns and their management implications in estuaries and intertidal wetlands. Continuous records over several decades allow for the identification and evaluation of long-term trends, enhancing monitoring effectiveness and improving inputs for management measures.