Monitoring and Quantifying the Fluvio-Geomorphological Changes in a Torrent Channel Using Images from Unmanned Aerial Vehicles

Abstract

The study attempts to monitor geomorphological changes (e.g., erosion/deposition) with innovative tools at a typical Mediterranean torrent. The torrent’s geomorphological conditions are studied for an entire affected stream reach. The investigation utilizes two different environments/point views: (a) traditional terrestrial and (b) innovative aerial. The traditional methods include erosion pins at streambanks and field cross-section measurements of the stream channel. For the innovative methods, utilizing an unmanned aerial vehicle, in order to monitor the geomorphologic changes in the entire reach during different days over the last 3 years (2020–2022), there was a total of six flights. The results from innovative methods showcase the episodic nature of stream channel changes since erosion and deposition were captured during the different monitoring periods. Even during one flight in one cross-section, the stream bed and two banks in many cases experienced different changes. The significant erosion and deposition recorded showcase the disequilibrium in the torrent. In addition, the impact of the anthropogenic structure (Irish bridge) is evident, since upstream, more substantial deposition was recorded compared to downstream. The similarity of the results between the innovative method and the traditional methods indicates the method’s effectiveness and the potential usefulness in using UAV images for stream bank and bed monitoring. One of the biggest advantages is the ability to monitor the entire reach at substantially lower costs and time compared to the traditional methods. Still, more testing needs to be conducted in different stream and river environments to better refine the method in order to be adopted by land and water managers to be used for stream and river monitoring.