Relating side scan sonar backscatter data to geotechnical properties for the investigation of surficial seabed sediments

Side scan sonar is a common tool for seafloor imaging and surveying due its efficiency and high resolution. The backscatter information from side scan sonar enables to identify sediment types and seabed roughness, often used to study sediment dynamics. Theory suggests that side scan sonar backscatter can be correlated to the geotechnical properties of the seabed surface. This could enhance the prediction of erodibility and efficiency of seabed sediment characterization, considering that side scan sonar can offer large spatial coverage in a short time. In this study, high-frequency (1000 kHz) side scan sonar backscatter data, sediment samples, and in-situ seabed strength profiles were collected of the seabed surface at ten locations. Statistical analysis of the backscatter data compared with geotechnical data showed trends between mean backscatter, soil strength, and textural sediment properties. Generally, mean backscatter increased when sediment strength and mean grain size increased and when water content and fines content decreased. However, roughness from bedforms, the presence of oysters, shell hash as well as variations in water content (i.e., porosity) of the seafloor heavily influenced the backscatter and sometimes masked any relationships with the strength properties directly.