Morphodynamics and evolution of Laga Beach, Ibarrangelu, Biscay

Abstract

The integrated analysis of sediment characteristics, shoreline morphodynamics, and dune evolution at Laga Beach highlights a coastal system governed by the interplay of waves, winds, tides, and human interventions. Seasonal contrasts, dry summer conditions that favour aeolian sedimentation versus high‐energy winter humid regimes driving erosion, combine with mesotidal and semidiurnal tidal modulation to produce alternate phases of beach stabilization and retreat. The increase in the frequency and intensity of sea-storms of the last years generates prolonged high-energy conditions that prevent the beach from re-establishing its lost equilibrium profile. Sediment sampling surveys reveal well- to moderately sorted medium sand on the intertidal and nearshore slopes, low-carbonate fine sand in the dunes, and subtidal deposits rich in bioclasts (containing over 50% carbonate). Long‐term monitoring of the evolution of the High-Tide Line (HTL) and the Dune-Toe (DT) demonstrates a pronounced planform rotation: coastal retreat exceeding 1 m between 1983–2001 under the influence of storm events (> 4 m) and anthropogenic pressures, followed by uniform progradation (~ 0.6 m/yr.) because of the 1998 dune actions. From 2006–2024, escalating storm intensity reversed this trend, eastern shoreline retreat up to 1 m/yr. while western sector advanced up to 8 m. Dune restoration measures (1998–2003), including boardwalks, fencing, sand traps and pioneer species planting drove seaward DT advances of 1.5 m/yr. in the eastern sector, whereas in the west sectors DT retreated landward with the same rate. Public surveys among beach local visitors indicate limited awareness of past interventions but strong willingness (≈ 80%) to support future conservation.