3D modeling and identification of post-dredging sediment layer types using hydroacoustic instruments

Sedimentation in harbor areas is a serious problem because it can interfere with ship navigation activities due to silting depth. Overcoming the siltation problem requires dredging to transport most sediment on the bottom of the water. In 2023, dredging was carried out to overcome the siltation problem, where the dredged layer was a soft layer and a small part of the hard layer. This research focuses on identifying the type of bottom sediment layer in PT Gresik Jasatama after dredging, modeling the sub-bottom layer and its depth and in addition, analyzing the difference in depth before and after dredging and interpreting the Side Scan Sonar image. The method used is an acoustic method, which consists of various instruments used to perform the analysis. The sub-bottom Profiler uses the acoustic wave reflection principle to determine the sediment layer type. Multibeam Echosounder is used to analyze the difference in bathymetry depth in 2021 and 2023 while analyzing the type of layer based on the digitation of the Sub-bottom Profiler. An echo-logger is used to analyze the difference in depth generated by low and high frequencies. Side Scan Sonar is used to provide a visual appearance of the shape of the seabed or objects on the seabed, and Backscatter MBES is used to analyze the type of sediment at the bottom of the water. Overlay between the difference data of Echologger, Sub-bottom Profiler, and bathymetry in 2023, a hard layer in the study area indicates dredging. In addition, the bathymetry measurement in the research area in 2021 was 1-8 meters, while in 2023, it was 7-12 meters, and the depth difference between the two depths was 4 meters. Side Scan Sonar interpretation shows the hard layer and soft layer by the borehole retrieval point, and the results of the water bottom characteristics show sediments in the form of gravel, gravel silty sand, clay, and sandy clay.