Wave-Climate–Driven Seasonal Morphodynamic Changes on an Estuarine Beach (Río de la Plata, Argentina)

Abstract

Estuaries represent transitional environments where fluvial, tidal, and wave processes interact in complex ways that differ markedly from open coasts. The Río de la Plata estuary, covering ~ 35,000 km², is one of the widest in the world. Along its southern shore, characterized by marshes and scarce sandy beaches, a pronounced erosional trend has recently been reported. The objective of this study is to identify the main processes controlling shoreline morphodynamics on a beach within a sector of a wide-fetch estuary. To this end, high-resolution, semi‐annual monitoring was conducted over the 2020–2024 period using Structure from Motion Multi-View Stereo (SfM‐MVS) techniques at a site in the middle Río de la Plata estuary, together with a simultaneous analysis of the wave climate. Results indicate a net erosive trend across the entire beach, with strong spatial variability. The northern sector experienced the most severe erosion (up to − 1.5 m), including profile lowering, escarpment retreat, and exposure of underlying claystones. Waveclimate parameters show mean values of breaking wave height (Hb = 0.52 m), breaking wave angle (θb = 70°), and incident wave energy flux (Pib = 1.37 kJ/ms). Seasonality is pronounced: mean wave height increases by 18% from winter (0.47 m) to summer (0.56 m), accompanied by a shift in wave direction of 3°, while the frequency of moderate and extreme events also increases during summer. Spatio-temporal change patterns are linked to shoreline geometry, orientation, human activities and local wave conditions. Increasing wind-driven wave activity suggests heightened erosive forcing and highlights the need to reconsider current coastal protection strategies.