Acoustic Observations of Fluid Mud and Interfacial Waves, Hangzhou Bay, China
Keywords:Cohesive sediments, fluid mud, suspended sediment, concentration, turbidity
By using an acoustic suspended sediment monitor (ASSM), layered structures were found in a proposed navigational channel at neap tide in Hangzhou Bay: downwards these are low concentration suspension; high concentration suspension; and fluid mud. Acoustic images revealed four different frequencies of interfacial waves. Type I is low-frequency interfacial wave between low concentration suspension and high concentration suspension. Type II is low frequency internal wave between high concentration suspension and mobile fluid mud. Type III is cautiously interpreted as low-frequency interfacial wave between mobile fluid mud and stationary fluid mud, on which are superimposed Type IV high-frequency interfacial wave. These interfacial waves act as the secondary dynamic forcing, which enhances local cohesive sediment resuspension and re-entrainment.