Geospatial Surveying for Floating Waste Mitigation Systems: A Multisensor Case Study on the Someșul Mare River

River pollution represents an environmental issue in Romania in recent years, particularly in the context of environmental protection and water quality monitoring. In the north-western region of Romania, upstream from the city of Beclean, the Someșul Mare River flows through numerous settlements. This has led to continuous changes in the river’s physical characteristics and an alarming increase in waste accumulation. The primary cause of this phenomenon is the local population’s improper waste disposal practices, where garbage is dumped directly into the riverbed. Even minor flood events mobilize and carry this waste downstream, further exacerbating the pollution problem. This research focuses on the collection of topographic and bathymetric data using photogrammetry, LiDAR, and sonar technologies, enabling a comprehensive analysis of the target area. These data support the mapping and planning of floating structures intended for biodiversity conservation and water management. Topographic surveys were conducted to provide accurate geospatial data from the field. To enhance topographical information, the UAS DJI Matrice M210 was used for collecting photogrammetric and LiDAR data, while underwater data was achieved using the Alpha Mi single beam echosounder system.