Monitoring coastal erosion-driven LULC and shoreline changes along the Lagos Coastal Corridor with Sentinel-2 imagery and DSAS

The Lagos Coastal Corridor is a 180-km stretch of low-lying coastline along the Atlantic Ocean in south-western Nigeria, increasingly threatened by coastal erosion driven by sea-level rise, intensified hydrodynamic forcing, and rapid urban expansion. This study evaluates Land Use and Land Cover (LULC) dynamics and erosion-driven shoreline change between 2015 and 2025 using Sentinel-2 multispectral imagery and digital coastal analysis techniques. At the Lagos State scale (3577 km²), supervised classification, validated at an overall accuracy of 93.27% (Kappa = 0.91), indicates a substantial increase in built-up areas from 22% (836.63 km²) in 2015 to 49% (1826.48 km²) in 2025, accompanied by declines in vegetation and water bodies and an expansion of wetland classes. Focusing specifically on the Lagos Coastal Corridor, results reveal more pronounced coastal transformation, with built-up areas increasing from 22% (283.61 km²) to 53% (683.96 km²) over the study period. Concurrently, vegetation cover declined from 31% (399.44 km²) to 19% (247.14 km²), while water bodies decreased from 19% (249.21 km²) to 4% (46.49 km²). Wetland extent increased from 9% (119.82 km²) to 24% (307.92 km²), likely reflecting inundation, sediment redistribution, and classification sensitivity in transitional coastal environments. Normalized difference vegetation index (NDVI) trends indicate deterioration in vegetation health, with the maximum decreasing from 0.89 to 0.86 and increased visibility of non-vegetated areas. DSAS-derived shoreline change analysis across 3658 valid transects confirmed significant spatial heterogeneity in coastal dynamics, with erosion rates reaching −25.1 m/yr along the Okun-Ajah and Ibeju-Lekki axis and accretion rates up to +32.29 m/yr in depositional zones, statistically validated by an independent samples t-test, t(3645) = −38.61, p < 0.001.