River Sand and Gravel Mining Monitoring Using Remote Sensing and UAVs

The development of methodologies for analyzing the evolution and pressures exerted on the river channel network is one of the main concerns of researchers today. The assessment of natural or artificial changes of river channels and beds plays an important role in environmental protection, but also in the implementation of integrated water resource management plans. Given the episodic and dynamic nature of river bank and bed erosion, along with the difficulty of reaching certain reaches, a methodological approach that uses aerial imagery, initially from satellite sources and afterwards from unmanned aerial vehicles, is proposed. This approach was utilized in a perennial river in Romania but also in an ephemeral torrent channel in Greece, in order to test the prevalent types of hydrographic network in the Mediterranean and Black Sea region. The methodology used was able to identify the location and the volume of the bed material extracted and the time frame in which it occurred. These encouraging results showcase an accurate but also relevantly low-cost monitoring method for illegal anthropogenic activities that can be easily adopted by the responsible authorities. The adoption of the method will contribute to the more efficient monitoring of river protection, by accurately and timely identifying areas of illegal river bed extraction that will enable authorities to enforce European Union and national legislation.