Experimental Study Demonstrating a Cost-Effective Approach for Generating 3D-Enhanced Models of Sediment Flushing Cones Using Model-Based SFM Photogrammetry

Abstract

Accurate measurements of sediment flushing cone geometry (SFCG) are essential for determining sediment removal efficiency in reservoirs. SFCG measurements are related to the point-to-point height that affects bathymetry accuracy, and they are used to develop a digital elevation model (DEM). Conventional bathymetry monitoring techniques require a longer time for data processing and output data with insufficient accuracy despite being inexpensive and simple. In the current research, a close-range photogrammetric method called the structure from motion (SFM) method was investigated to determine the SFCG in an experimental study. The regular geometric shape of a cube was used to verify the SFM. Additionally, measurements between model control points (MCPs) on the flushed sediment bed were compared with those from the SFM method. The results indicated that the calculated SFM values were consistent with the measured values. To determine the SFCG, two sets of images were captured with 70% average overlapping before and after the completion of each test. After processing and post-processing via the SFM tool AgiSoft Metashape, a georeferenced 3D model was achieved. The accuracy of the surveyed data in terms of the dimensions, cross-sections, and temporal developments of the sediment flushing cone was investigated to verify the SFM method. Finally, the results revealed good agreement (R2=0.99 and average error of 0.03–0.74 mm) between the DEMs created by the SFM method and the actual model.