Acoustic imaging of cohesive sediment resuspension and re-entrainment in the Changjiang Estuary, East China Sea

Vertical profiles of instantaneous cohesive suspension concentration, obtained from an acoustic suspended sediment monitor in the Changjiang Estuary, indicate that near-bed high-concentration suspensions consist of upper and lower high-concentration suspensions, separated by a natural breakpoint at ca. 2 g l-1. Acoustic images revealed near-bed high-frequency resuspension events of a few seconds, which contribute mainly to the formation of the lower near-bed high-concentration suspension. Upper and lower lutoclines are also indicative of re-entrainment of lower and upper high concentration suspension, respectively. Near-bed high-frequency resuspension is caused by turbulence, while re-entrainment is probably attributable to internal wave activity.