Unmanned aerial vehicle system-based remote sensing for monitoring landscape degradation

The uncontrolled water flooding in an abandoned open pit mine modifies the rock mass stability, causing rock wall falls and surface erosion that may affect great volumes of material. As regards Sardinia quarries, most of the open pit excavations need a recovery plan. The last mostly depends upon knowledge of the relationship between the geomorphological asset and the nature of weathering and related erosion processes. The aim of this paper is to evaluate the land degradation with a detailed photogrammetric survey based on Unmanned Aerial Vehicle System (UAS) to generate detailed 3D point cloud models. In this paper we focus mainly on the evolution of the surface erosion that affects an abandoned mine located in the SE Campidano Region (Sardinia-Italy), causing deep drainage and transformation of the landforms, followed by the transportation of material outside of the mining area. The monitoring of the quarry during the last five years allowed to compare different digital surface models, to evaluate the landscape degradation processes in act. The application of UAS survey was developed through several periodical flights, using the same waypoints grid. In this way we obtained very accurate and comparable photogrammetric 3D digital models to highlight in detail the different processes taking place. The comparison of the digital models allowed an accurate analysis of the surface erosion and accumulation processes occurring inside the quarry. This work is intended to be a preliminary study for the planning of an effective future recovery project to minimize hazards related to mine closure processes.