Non-Uniform Morphodynamics of the Negro River Estuary Mouth, Argentina (2013-2021)

Estuarine mouths exhibit complex morphodynamics controlled by the interplay of river discharge, tides, longshore drift, and sediment transport, which can influence navigation, ecology, and coastal management. The objective of this study is to document the spatio-temporal evolution of the Negro River mouth by examining variations in the river’s width at different points along the estuary and analyzing the movement of sediment lobes present in the mouth. To achieve this, 62 Landsat-8 images (2013–2021) were analyzed, combining Mann-Kendall trend tests with multifractal metrics to assess persistence, complexity, and asymmetry along four transect sections (W1–W4). Results reveal distinct morphodynamic domains: W1 shows sustained widening, high complexity, and right-skewed variability associated with river–tide–sediment interactions; W2 exhibits dynamic equilibrium with no net trend, minimal complexity, and left-skewed behavior; W3 resumes widening under strong tidal and longshore influence; and W4 displays pronounced narrowing, low complexity, and a regime dominated by sandbank progradation. High persistence values (H ≥ 0.85) indicate strong system inertia, although longer-term cycles may not be captured. Direct local anthropogenic impacts were negligible, but river regulation and droughts may modulate flow patterns. These findings demonstrate the spatially heterogeneous evolution of the estuary mouth, providing a quantitative framework for attributing morphodynamic processes. The methodology and results are applicable to other delta-influenced estuaries, supporting improved understanding and management of estuarine systems under fluvial, tidal, and sedimentary controls.