Numerical Assessment of Turbidity Currents Generated by Cutter Suction Dredgers
Type:
Presented during:
CEDA Dredging Days 2024
Authors:
M. Mahgoub, S. Alhaddad and G.H. Keetels
Abstract
Dredging-induced sediment plumes can cause severe damage to the aquatic environment; turbidity-related light reduction decreases the photosynthesis activities and oxygen release, which in turn negatively affects the growth of aquatic flora and fauna. In addition, the settlement of sediment particles over sensitive aquatic habitats like coral reefs could cause smothering of such valuable ecosystems (Erftemeijer et al., 2012; Jones et al., 2019; Becker et al., 2015). To anticipate this damage, an Environmental Impact Assessment (EIA) is carried out. EIA includes far-field hydrodynamic and sediment transport modeling of the plume to predict the spatial distribution of the sediment concentration levels and the temporal evolution. Based on these far-field predictions, an ecological assessment is performed, as each environmental receptor can sustain certain stresses (sediment concentration) for certain periods. Sediment plumes can be generated during one or more of the three processes of dredging: excavating, transporting, and reallocating bed material. A key input to the far-field modeling process is the rate of sediment release due to dredging activities, i.e. the source-term which is dependent on the near-field dynamics around the dredging equipment. Accurate estimation of the source-term is essential for a realistic EIA and requires a good representation of the physical processes and resuspension mechanisms taking place in the near-field environment. Any uncertainty in the source-term prediction will propagate through the whole EIA process and may result in misestimated stresses and environmental impacts.
Keywords: Turbidity blumes, turbidity currents, environmental impact assessment, sensitivity analysis