Terraced landscapes located in areas of great value for touristic purposes as an irreversible practice

Since Neolithic, terraced landscapes have been an essential element for moulding mountain or steep slope into habitable arable areas. Over the last decades, they have been subjected to a quick abandonment because of their inadequate economic competitiveness causing a gap in their maintenance and, consequently, incrementing the hydrogeological instability of those areas. Minori is a small municipality (256 ha), protected by UNESCO, located in Amalfi Coast. That area is well known not only for the beauty of its territory but also for some catastrophic raining events, like in 1954 when a rain shower of 500 mm topped up to 24 hours. The current research work intends to analyse the landscape changes in Minori over sixty year period (1956 - 2017) for assessing the new values taken on the land use and the agricultural sites. A detailed orthophoto and a high resolution Digital Elevation Model (DEM) of the study area have been reconstructed using the historical photogrammetric photos of 1954, acquired by the Italian Military Geographic Institute (IGM), and the aerial photogrammetric pictures of 2017, obtained by an own flight. DEM and orthophoto have been reconstructed applying Agisoft Photoscan Professional. The resolution of the generated DEM is equal to 0.48 and 0.1 m for 1956 and 2017, respectively. The orthophoto resolution is of 0.24 and 0.07 for 1956 and 2017, respectively. Comparing the generated products of the two periods, it is pointed out that terraces extension has not been amended, while the amount of human constructions have increased of about 800%. To give a first idea of the most vulnerable areas to be investigated more in depth through simulation procedures, a first proposal of an expeditious index of vulnerability (EVI) has been introduced and tested. It is based on the ratio between the amount of surface occupied by buildings and the amount of areas subjected to a debris flow event. The increase of the vulnerability, exposure values and probability of accident occurring involve a risk rise.