Unmanned-System-Based Solution for Coastal Submerged Outfall Detection

Land-based sewage discharge is closely related to the marine environment, and it is necessary to monitor, evaluate, and regulate this discharge in a scientific and comprehensive manner. However, it is often difficult to effectively detect and monitor the large number and concealment of submerged coastal outfalls. To address this challenge, we present an unmanned system submerged outfall detection method utilizing an unmanned aerial vehicle (UAV) thermal infrared sensor and an unmanned surface vehicle (USV) side-scan sonar operating in concert. Taking a typical coastal area of Shanghai submerged outfall detection as an example, the unmanned system detection methods identified 51 suspected submerged outfalls in a shoreline survey area of approximately 35.5 km, of which 49 were reviewed and confirmed to exist, with a survey success rate of 96.1%. Specifically, 18 newly discovered submerged outfalls and 31 known submerged outfalls were also identified, i.e., the success rate for the registered submerged outfalls reached 100%. The data not only verified the effectiveness and reliability of the detection method, but also provided essential data for transparent and standardized sewage discharge, scientific and accurate sewage treatment, and protection of the water quality and biodiversity in coastal areas.