Research on Underwater Flaw Detection in the Forebay of Tatay Hydropower Station Based on Multibeam Bathymetry

To resolve the challenges posed by the complex underwater structures of dams, where traditional contact-based inspection methods carry high risks, low efficiency, and insufficient accuracy, research is being conducted to explore the feasibility of developing a non-contact underwater flaw detection method. This approach integrates a high-resolution multibeam bathymetric system (Ultra High Density mode), high-precision positioning and attitude determination, and sonar imaging. An automated defect detection method based on multi-beam 3D point cloud contour line recognition was developed. This approach establishes high-resolution 3D models and is validated through manual inspection, underwater camera imaging, and automated defect identification, precise localisation, and quantitative analysis. A case study involving safety inspection of a minor seepage pit upstream of a foreign hydropower dam demonstrated: the system's bathymetric accuracy exceeded 0.5% × water depth, with a model resolution of 0.1m. Flaw detection, localisation, and quantitative analysis proved reliable, while the automated recognition algorithm matched manual identification, confirming the method's viability. This provides high-precision data support for subsequent emergency repair works and dam safety diagnostics, offering valuable technical reference for similar engineering flaw detection in steep, deep-water environments.