Using multibeam acoustic remotely sensed data to investigate seabed sediment grain size characteristics

Acoustic remote sensing is the only effective technique to investigate the deep seabed. Modern high-frequency multibeam echo-sounders transmit and receive backscatter signals from hundreds of narrow-angle beams which generate small footprints on the seabed. They can produce bathymetry and backscatter data with a spatial resolution around 2% of water depth, which enables us to map the seabed with great detail and accuracy. After calibration, the backscatter intensity is largely controlled by three seabed physical properties: the acoustic impedance contrast (often called 'hardness'), apparent interface roughness (relative to acoustic frequency) and volume inhomogeneity [6, 7, 11]. These seabed physical properties are directly related to sediment grain size.