RAPID COASTAL MORPHODYNAMICS: DIVERSE CASE STUDIES AND APPROACHES FOR SEDIMENTARY DYNAMICS (REA) ASSESSMENT

Coastal environments are inherently dynamic, shaped by natural forces such as waves, currents, and tides. Rapid Environmental Assessment (REA) offers a practical method for evaluating sediment transport impacts on coastal landforms, habitats, and infrastructure, particularly in the context of episodic events and transgressive settings linked to global sea-level rise. This work highlights three case studies in dynamic coastal systems using aerial imagery and detailed topographical surveys to assess morphology, sediment budgets, and ecological changes. (1) Piscinas Dune (Sardinia, Italy): UAV surveys and regional lidar data (2008–2024) provided quantitative insights into the migration of a unique transgressive dunefield. Key findings include significant erosion of the stoss slope and a self-regulating depositional system through lobes. Although sand drift risks were initially identified, recent data suggest diminished threats to nearby tourist areas. (2) Martignano Barrier Island (Northern Italy): monitoring captured morphological evolution of a washover fan formed following storm surges, revealing the barrier island's resilience capacity to transgressive phenomena. The beach-dune system with vegetation recovered completely in eight years, resulting in the formation of a relict washover fan and the establishment of a new habitat for Greater Flamingos. This example highlights the ecological advantages of episodic events in the safeguarding of biodiversity. (3) Lignano Beach (Northern Italy): seasonal defences (sandbags and geotextile tubes) were evaluated for their effectiveness against storm surges. Findings indicate that sandbags are more resilient than geotextile tubes, which fail completely upon breach. Recommendations include designing dissipative ramps with a gradient of 1:40 and placing defences at a minimum height of 2 metres to mitigate erosion effectively. These case studies demonstrate the importance of a REA in guiding coastal management, combining UAV surveys, sediment budget analysis, and ecological assessments. The proposed protocols aim to balance human use with natural preservation, providing critical data for informed decision-making in the face of accelerating sea-level rise and extreme weather events.