Coastal Engineering Vol. 208 15 June 2026 Paper 105018
Wave climate change and sea-level rise (SLR) are expected to alter coastal morphodynamics over the coming decades in complex, non-linear ways, particularly along embayed beaches constrained by geological boundaries. This study quantifies the relative influence of wave direction, wave height, and SLR on storm-driven shoreline change and sediment transport within the open-ocean Port Fairy embayment, south-eastern Australia, using a process-based MIKE 21 coupled wave–hydrodynamic–sediment transport model with dynamic morphological updating. 35 storm scenarios of 30-h duration were simulated, systematically varying wave direction (Dm = 188°–208°), significant wave height (Hs = 2.8–6.3 m), and SLR (+0.21 m) to assess direction-dependent thresholds and non-linear interactions under mid-century (2050) conditions. Future scenarios apply mid-century SLR (+0.21 m) to present-day morphology across modal, storm, and extreme wave conditions, with extreme scenarios additionally incorporating projected wave climate intensification (+5% wave height and period), capturing storm-event hydrodynamic modifications without simulating multi-decadal shoreface translation. Results show that wave direction exerts a significant control on the spatial distribution of storm response, with ±10° shifts producing opposing erosion–accretion patterns. A critical threshold at Hs ≈ 4–4.6 m marked the transition from local to embayment-wide sediment mobilisation. Southerly storms (Dm = 188°–193°) generated widespread erosion, while south-westerly storms (Dm = 203°–208°) enhanced sediment retention through alongshore redistribution. Under mid-century SLR (+0.21 m), modal wave conditions transformed previously stable zones into erosional areas, while southerly storms intensified offshore export, demonstrating that elevated water levels reorganise storm-driven sediment pathways rather than uniformly amplifying erosion. Wave direction, wave height, and SLR each produced distinct effects on event-scale morphodynamic response: 1) directional shifts reorganised where erosion and accretion occurred, 2) wave height controlled the intensity and spatial extent of sediment mobilisation, and 3) SLR modified the system’s sensitivity to both. These findings demonstrate that projected mid-century changes in wave climate direction must be considered alongside wave height and SLR to assess storm-scale resilience and stability of embayed coasts, with implications for adaptive, directionally sensitive coastal management under climate change.
