Marine Dredging Sedimentation

Sedimentation generated during marine dredging operations may occur both during the dredging process and during offshore disposal (dumping) of dredged materials. Dredging is performed for a wide range of purposes, including deepening and widening navigation channels, trenching for submarine pipelines, offshore drilling, offshore platform construction, submarine pipeline protection, seabed material extraction, and other marine engineering activities. The magnitude of sediment resuspension largely depends on the type of dredging equipment employed. Dredging methods include mechanical excavation, high-pressure water jetting, cutter dredging, suction dredging, material fragmentation, and grab (bucket) dredging. The greatest sediment resuspension generally occurs when dredging involves high-pressure water jetting or mechanical fragmentation of seabed materials. Likewise, hydraulic suction dredgers that discharge dredged materials into the water column can substantially increase suspended sediment concentrations. Consequently, selecting the appropriate dredging equipment is essential not only for maximizing operational efficiency but also for minimizing environmental impacts. Similarly, offshore disposal sites for dredged materials should be carefully selected by considering hydrodynamic conditions, including currents and waves, together with potential environmental impacts.

Numerical modeling provides a robust scientific basis for selecting the most appropriate dredging method and determining environmentally suitable offshore disposal sites, thereby improving the efficiency and effectiveness of dredging operations. Modeling scenarios are developed according to dredging techniques, operational procedures, and sediment disposal strategies. Numerical simulations predict sediment transport pathways, suspended sediment plumes, and deposition patterns on the seabed. If the predicted sediment plume avoids environmentally sensitive areas and does not create undesirable sediment accumulation or navigation hazards elsewhere, the selected dredging strategy can be considered environmentally sound and operationally effective.

The modeling framework typically integrates Hydrodynamic Models to simulate currents and water-level variations, Spectral Wave Models to evaluate wave-induced circulation and sediment resuspension, and Bed Sediment Transport, Suspended Sediment Transport, and Particle Tracking Models to simulate sediment transport processes and deposition characteristics. Ecosystem Models are then used to assess the impacts of sedimentation on the physical, chemical, and biological conditions of the aquatic environment and to evaluate potential ecological consequences.

The numerical modeling modules commonly applied for marine dredging sedimentation assessments include: