*2.3. The Test Areas*

To assess the most recent shoreline changes with the use of UAV-derived data, we selected two test areas (A and B, Figures 1 and 2). These test areas allowed us to investigate two different situations: one concerning conditions of essential stability for both the shoreline and the beach–dune system, and the other relating to evident erosion and destabilization, either recent or perhaps ongoing, which involve previously stable coastal segments.

Test area A falls under segment S3 (northern Molise coast, Figure 2) and is part of the Petacciato coastline. It consists in a 400 m long stretch of coast located 500 m south of Marina di Petacciato. This area is characterized by a sandy beach about 30 m wide, supported by a well-preserved dune system that is wider than 10 m and up to 4 m high.

Test area B is located along the southern Molise coast in the northernmost part of segment 9 (Figure 2), at approximately 1.5 km south of the Campomarino touristic port, and is part of erosion area E4, indicated by Buccino et al. (2020) [10]. It consists in an approximately 200 m long coastal stretch that is characterized by a 6–25 m wide sandy beach and an up to 4 m high dune system, whose original dune front has been replaced by a sub-vertical erosion scarp up to 2.5 m high that clearly separates the dune from the backshore. In front of test area B, 160–200 m from the shoreline, there are three breakwaters. They belong to a row of nine (originally) emerged and detached breakwaters approximately 700 m long, oriented slightly obliquely to the coast, and placed between 2001 and 2005. Furthermore, in front of the central part of area B, a detached groin (placed in 2011–2014) is located approximately 30 m from the shoreline (for further details, see Section 4.2).
