Fluid Mud Sondes & Acoustic Imaging Methods for Coastal Dredging.

A new method or protocol for measuring fluid mud and muck using passive sondes and an acoustic imaging method is described. Results made during two recent dredging projects are reported. The desired result in terms of environmental remediation dredging was to reduce the movement of fluid mud and muck. The movement of fluid mud and muck is measured quantitatively in terms of a flux density (mass L^-2 T^-1) using in-situ direct sondes. The muck management goal was to measure fluid mud and muck movement reduction (MMR) in coastal Indian River Lagoon. Prior fluid mud methods rely upon surrogate or indirect methods and have limitations because they sample a point in space at an instant in time. The use of vertical and horizontal sondes deployed for 12-48 hours represent a monitoring protocol for measuring fluid mud and muck movement. In conjunction with the vertical and horizontal placements of sondes, stationary acoustic fanbeam imaging was conducted. The fan beam imaging shows the presence of moving nephelometric layers and a moving bottom lutocline. This near bottom deformable fluid mud layer is thus measured with the sondes to directly estimate directional fluxes of dense particulate fluidized material in the coastal bottom boundary layer. Results of measuring deposition and resuspended fluxes of total particulate matter fluxes in the bottom boundary layer is also presented at a transect and at individual stations. [ABSTRACT FROM AUTHOR]