Abstract
This study provides a detailed integrated analysis of the erosional processes affecting the volcanoclastic headlands of a pocket beach, of a typical Tyrrhenian volcanic island (Ventotene, south Italy). It compares the survey carried out in 2012 and the recent landslides that occurred in 2018–2020. The studied tuff cliff is characterised by steep, up to overhanging walls affected by a fracture network, which locally isolates blocks in precarious equilibrium. The stability conditions of the southern Cala Nave Bay sea cliff were evaluated by integrating a geological field survey, structural analysis of discontinuities, and a detailed topographic survey consisting of a terrestrial laser scanner (TLS) and photogrammetry data acquisition and processing, providing a three-dimensional (3D) model of the sea cliff. The 3D model of the area affected by the recent landslides was created using proximity photogrammetry, the Structure for Motion (SfM) methodology. The fracture network was represented by using high-resolution digital models and projected to realize geostructural vertical mapping of the cliff. The data acquired in 2012 were more recently compared with further surveys carried out, following rock failures that occurred in winter 2019–2020. The detachment planes and failure modalities coincide perfectly with the ones previously assessed. The applied techniques and the comparison with the recent rock failures have proven to be important in defining these conditions to address risk mitigation interventions.
Highlights
Embayed pocket beaches in rocky coasts are highly attractive segments of coasts, and are tourism sites to drive the economy, especially on small islands [1]. These beaches are frequently backed by rocky headlands [2,3,4,5,6], which are characterised by rapid geomorphological evolution due to waves and weathering action, which result in failure processes and irreversible loss of land [7]
The base of the cliff is covered by slope breccia and gravelly beach deposits together with meter scale tuff blocks originated by rockfall
This study provided a detailed integrated analysis of the erosional processes affecting the evolution of coastal morphology in a typical Tyrrhenian volcanic island (Ventotene, south Italy)
Summary
Embayed pocket beaches in rocky coasts are highly attractive segments of coasts, and are tourism sites to drive the economy, especially on small islands [1]. These beaches are frequently backed by rocky headlands [2,3,4,5,6], which are characterised by rapid geomorphological evolution due to waves and weathering action, which result in failure processes and irreversible loss of land [7]. Rocky coasts may reach steep slopes; their response to wave action is further affected by the discontinuity (fracture and fault) network [8]. Where the bathymetric setting is favourable, sandy beaches develop and protect cliffs from further marine erosion [13]
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